The Classification of Lower Organisms Ernst Hkinrich Haickei, in 1874 From Rolschc (1906). By permission of Macrae Smith Company. C f 3 The Classification of LOWER ORGANISMS By HERBERT FAULKNER COPELAND \ PACIFIC ^., ^,kfi^..^ BOOKS PALO ALTO, CALIFORNIA Copyright 1956 by Herbert F. Copeland Library of Congress Catalog Card Number 56-7944 Published by PACIFIC BOOKS Palo Alto, California Printed and bound in the United States of America CONTENTS Chapter Page I. Introduction 1 II. An Essay on Nomenclature 6 III. Kingdom Mychota 12 Phylum Archezoa 17 Class 1. Schizophyta 18 Order 1. Schizosporea 18 Order 2. Actinomycetalea 24 Order 3. Caulobacterialea 25 Class 2. Myxoschizomycetes 27 Order 1. Myxobactralea 27 Order 2. Spirochaetalea 28 Class 3. Archiplastidea 29 Order 1. Rhodobacteria 31 Order 2. Sphaerotilalea 33 Order 3. Coccogonea 33 Order 4. Gloiophycea 33 IV. Kingdom Protoctista 37 V. Phylum Rhodophyta 40 Class 1. Bangialea 41 Order Bangiacea 41 Class 2. Heterocarpea 44 Order 1. Cryptospermea 47 Order 2. Sphaerococcoidea 47 Order 3. Gelidialea 49 Order 4. Furccllariea 50 Order 5. Coeloblastea 51 Order 6. Floridea 51 VI. Phylum Phaeophyta 53 Class 1. Heterokonta 55 Order 1. Ochromonadalea 57 Order 2. Silicoflagellata 61 Order 3. Vaucheriacea 63 Order 4. Choanoflagellata 67 Order 5. Hyphochytrialea 69 Class 2. Bacillariacea 69 Order 1. Disciformia 73 Order 2. Diatomea 74 Class 3. Oomycetes 76 Order 1. Saprolegnina 77 Order 2. Peronosporina 80 Order 3. Lagenidialea 81 Class 4. Melanophycea 82 Order 1 . Phaeozoosporea 86 Order 2. Sphacelarialea 86 Order 3. Dictyotea 86 Order 4. Sporochnoidea 87 V ly Chapter Page Orders. Cutlerialea 88 Order 6. Laminariea 89 Order 7. Fucoidea 91 VII. Phylum Pyrrhophyta 94 Class Mastigophora 95 Order 1. Cryptomonadalea 96 Order 2. Adiniferidea 98 Order 3. Cystoflagellata 99 Order 4. Cilioflagellata 102 Order 5. Astoma 105 VIII. Phylum Opisthokonta 110 Class Archimycetes Ill Order 1. Monoblepharidalea Ill Order 2. Chytridinea 113 IX. Phylum Inophyta 119 Class 1. Zygomycetes 121 Order 1. Mucorina 121 Order 2. Entomophthorinea 124 Class 2. Ascomycetes 125 Order 1. Endomycetalea 129 Order 2. Mucedines 130 Order 3. Perisporiacea 131 Order 4. Phacidialea 133 Order 5. Cupulata 134 Order 6. Exoascalea 137 Order 7. Sclerocarpa 137 Order 8. Laboulbenialea 140 Class 3. Hyphomycetes 140 Order 1. Phomatalea .... 141 Order 2. Melanconialea 141 Order 3. Nematothecia 141 Class 4. Basidiomycetes 142 Order 1. Protobasidiomycetes 146 Order 2. Hypodermia 147 Order 3. Ustilaginea 149 Order 4. Tremcllina 149 Order 5. Dacryomycetalea 150 Order 6. Fungi 150 Order 7. Dermatocarpa 152 X. Phylum Protoplasta 157 Class 1. Zoomastigoda 157 Order 1. Rhizoflagellata 158 Order 2. Polymastigida 163 Order 3. Trichomonadina 166 Order 4. Hypcrmastiglna 168 Class 2. Mycetozoa 171 Order 1. Enteridiea 171 Order 2. Exosporea 177 vi Chapter Page Order 3. Phytomyxida 177 Class 3. Rhizopoda 179 Order 1. Monosomatia 183 Order 2. Miliolidea 185 Order 3. Foraminifera . . . 185 Order 4. Globigerinidea 187 Order 5. Nummulidnidea 188 Class 4. Heliozoa 189 Order 1. Radioflagellata 190 Order 2. Radiolaria 194 Order 3. Acantharia 195 Order 4. Monopylaria 198 Orders. Phaeosphaeria 198 Class 5. Sarkodina 200 Order 1. Nuda 201 Order 2. Lampramoebae 205 XI. Phylum Fungilli 206 Class 1. Sporozoa 207 Order 1. Oligosporea 209 Order 2. Polysporea 211 Order 3. Gymnosporidiida 211 Order 4. Dolichocystida 214 Orders. Schizogregarinida 215 Order 6. Monocystidea 215 Order 7. Polycystidea 216 Order 8. Haplosporidiidea 218 Class 2. Neosporidia 219 Order 1. Phaenocystes 219 Order 2. Actinomyxida 221 Order 3. Cryptocystes 222 XII. Phylum Ciliophora 223 Class 1. Infusoria 228 Order 1. Opalinalea 228 Order 2. Holotricha 229 Order 3. Heterotricha 230 Order 4. Hypotricha 233 Order 5. Stomatoda 233 Class 2. Tentaculifera 235 Order Suctoria 235 List of Nomenclatural Novelties 237 Bibliography 238 Index 271 VII LIST OF ILLUSTRATIONS Portrait of Ernst Heinrich Haeckel Frontispiece Figure Page 1. Structure of cells of blue-green algae 13 2. Photographs of Escherichia coli . . . 15 3. Caulobacterialea; Myxobactralea; Cristispira Veneris 26 4. Coccogonea; Gloiophycea 32 5. Bangialea 42 6. Nuclear phenomena in Polysiphonia violacea 45 7. Heterocarpea 48 8. Ochromonadalea 54 9. Ochromonadalea; Silicoflagellata 56 10. Vaucheriacea 64 11. Choanoflagellata 68 12. Hyphochytrialea 70 13. Bacillariacea 72 14. Oomycetes 78 15. Stages of nuclear division in Stypocaulon 84 16. Familiar kelps of Pacific North America 90 17. Microscopic reproductive structures of Laminaria yezoensis ... 92 18. Cryptomonadalea 97 19. Cystoflagellata; Cilioflagellata 104 20. Astoma 106 21. Astoma 108 22. Monoblepharidalea 114 23. Chytridinea 116 24. Zygomycetes 122 25. Ascomycetes 132 26. Ascomycetes 136 27. Mycosphaerella personata 138 28. Basidiomycetes 144 29. Fruits of Agaricacea 153 30. Rhizoflagellata 160 31. Polymastigida; Trichomonadina 164 32. Hypermastigina 170 33. Mycetozoa 176 34. Ceratiomyxafruticulosa 178 35. Life cycle of "Tretomphalus" i. e., Discorbis or Cymbalo por a . . . 180 36. Shells of Rhizopoda 184 37. Radioflagellata 192 38. Radiolaria; Acantharia; Monopylaria; Phaeosphaeria 196 39. Chaos Protheus 200 40. Sarkodina 204 41. Life cycle of Goussia Schuhergi 208 42. LUe cycle of Plasmodium; Babesia bigemina 212 43. Life cycle of Myxoceros Blennius 220 44. Infusoria, order Hypotricha 232 45. Tokophrya Lemnarum 234 ix Chapter I INTRODUCTION The purpose of this work is to persuade the community of biologists that the ac- cepted primary classification of living things as two kingdoms, plants and animals, should be abandoned; that the kingdoms of plants and animals are to be given definite limits, and that the organisms excluded from them are to be organized as two other kingdoms. The names of the additional kingdoms, as fixed by generally accepted principles of nomenclature, appear to be respectively Mychota and Protoctista. These ideas originated, so far as I am concerned, in the instruction of Edwin Bingham Copeland, my father, who, when I was scarcely of high school age, admitted me to his college course in elementary botany. He thought it right to teach freshmen the fundamental principles of classification. These include the following: The kinds of organisms constitute a system of groups; the groups and the system exist in nature, and are to be discovered by man, not devised or constructed. The system is of a definite and peculiar pattern. By every feature of this pattern, we are inductively convinced that the kinds of organisms, the groups, and the system are products of evolution. It is this system that is properly designated the natural system or the natural classification of organisms. It is only by metaphor or ellipsis that these terms can be applied to systems formulated by men and published in books. Men have developed a classification of organisms which may be called the taxo- nomic system. Its function — the purpose for which men have constructed it — is to serve as an index to all that is known about organisms. This system is subject to cer- tain conventions which experience has shown to be expedient. Among natural groups, there are intergradations; taxonomic groups are conceived as sharply limited. Natural groups are not of definite grades; taxonomic groups are assigned to grades. When we say that Pisces and Filicineae are classes, we are expressing a fact of human conven- ience, not a fact of nature. The names assigned to groups are obviously conventional. Since the taxonomic system represents knowledge, and since knowledge is ad- vancing, this system is inherently subject to change. It is the right and duty of every person who thinks that the taxonomic system can be improved to propose to change it. A salutary convention requires that proposals in taxonomy be unequivocal: one proposes a change by publishing it as in effect; it comes actually into effect in the degree that the generality of students of classification accept it. The changes which are accepted are those which appear to make the taxonomic system, within its conven- tions, a better representation of the natural system. Different presentations of the taxonomic system are related to the natural system as pictures of a tree, by artists of different degrees of skill or of different schools, are related to the actual tree; the taxonomic system is a conventionalized representation of the natural system so far as the natural system is known. These statements are intended to make several points. First, as a personal matter, advancement of knowledge of natural classification, and corresponding improvement of the taxonomic system, have been my purpose during the greater part of a normal lifetime. Secondly, I have pursued this purpose, and continue to pursue it, under the guidance of principles which all students of classification will accept (perhaps with variations in the words in which they are stated). In the third place, I have tried to answer the question which scientists other than students of classification, and likewise the laity, are always asking us: why can one not leave accepted classification undis- 2 ] The Classification of Lower Organisms turbed? One proposes changes in order to express what one supposes to be improved knowledge of the kinds of organisms which belong together as facts of nature. If here I place bacteria in a different kingdom from plants, and Infusoria in a different king- dom from animals, it is because I believe that everyone will have a better understand- ing of each of these four groups if he does not think of any two of them as belonging to the same kingdom. The course of evolution believed to have produced those features of the natural system to which the present work gives taxonomic expression is next to be described. Life originated on this earth, by natural processes, under conditions other than those of the present, once only. These are the opinions of Oparin ( 1938) 1, and appear sound, although some of the details which he suggested may not be. When the crust of the earth first became cool, it was covered by an atmosphere of ammonia, water vapor, and methane, and by an ocean containing the gases in the atmosphere above it and minerals dissolved from the crust. This is to state the hypotheses that organic matter in the form of methane is older than life; and that whereas conditions on the face of the earth tend now to cause oxidation, they tended originally to cause reduc- tion. In a medium of the nature of the supposed primitive ocean, spontanous chemical changes will occur and produce organic compounds of considerable complexity: this has repeatedly been demonstrated by experiment. To convert a solution of ammonia, methane, and minerals into protoplasm, Oparin postulates a very long series of changes, producing successively more complicated compounds and mixtures, and re- quiring perhaps hundreds of millions of years. The changes are conceived as acci- dents; they are supposed to have been probable accidents, like throwing a seven at dice, not events which could only very rarely occur by accident, like throwing twenty sevens in succession. By supposing that some of these processes used up the m.aterials neces- sary for them, Oparin provides an explanation of the single origin of life: we are confident that all life is of one origin, because all protoplasm is of the same general nature, and all life consists of essentially the same processes. The course of events described would have yielded, as the original form of life, anaerobic saprophytes; this is in harmony with the fact that anaerobic energesis is in a sense the basic metabolic process. The original organisms would scarcely have possessed nuclei: Oparin's theories indicate, as the most primitive form of life which has been able to survive, the anaerobic bacteria. The anaerobic bacteria are indeed very far removed from any lifeless things; their protoplasm and their metabolism are fundamentally the same as ours. Life requires energy. Under anaerobic conditions, an organism can obtain energy by converting sugars to alcohol, but it can not use alcohol as a source of energy. This example means that anaerobic energesis yields energy in strictly limited quantity and produces incompletely oxidized compounds. So long as all life was anaerobic, it was engaged in converting the organic matter upon which it depended into forms which it could not use; life under these conditions, at least if they persisted for any great period of time, was surely very sluggish. A further scries of changes in the metabolic system, occurring accidentally in certain organisms and preserved by natural selec- tion, brought photosynthesis into existence. The purple bacteria are believed to rep- resent stages in the evolution of photosynthesis, which exists in its fully developed form, involving the release of elemental oxygen, in the blue-green algae. Once photo- ^ Dates in parentheses are references to works which have been consulted and listed in the bibliography. Introduction [ 3 synthesis was established in certain organisms, aerobic energesis became possible both to these and to others. This made possible a manner of life more vigorously active than before. The inconsiderable groups of autotrophic bacteria — the organisms which live by oxidizing inorganic matter — appear to be secondary developments dependent upon the existence of photosynthesis. The organisms whose origin has been suggested thus far — the ordinary bacteria, anaerobic and aerobic, the autotrophic bacteria, the purple bacteria, and the blue- green algae — are relatively simple in structure and function; all consist of minute physiologically independent cells. The first step in the evolution of more complex organisms was the evolution of the nucleus. Morphologically, the nucleus is a part of a protoplast which is set apart by a mem- brane and which originates ordinarily by division of a pre-existent nucleus in the manner called mitosis. In this process, a definite number of definite chromosomes appear and undergo equal division. The nucleus exercises control over the protoplast in which it lies. Its controlling action depends upon the chromosomes which go into it, and mitosis has the effect that all nuclei which are derived from one original nu- cleus strictly by normal processes of mitosis are identical in the controlling effects which they exert. Thus the nucleus serves for the precise transmission of a compli- cated heredity. Beside mitosis, there are two other processes — two only — meiosis and karyogamy, by which nuclei may produce other normal and enduringly viable nuclei. In a sequence of generations of individuals sexually produced, these processes occur alternately, each one at one point in each cycle of sexual i-eproductlon. Mendelian heredity is produced by changes, in the sets of chromosomes (or parts of chromo- somes) in individual nuclei, which occur during meiosis and karyogamy. The role of the nucleus in sexual reproduction is one of its essential characters: the nucleus is re- lated to sexual reproduction, including Mendelian heredity, as structure to function. The existence of organisms without nuclei shows that the nucleus evolved after life did: it did not evolve at the same time as protoplasm. The essential uniformity of the nucleus and of its association with sexual reproduction shows that these things evolved only once, and together. There are a very few organisms, as Porphyridium and Prasiola, in which the presence or absence of nuclei is not certain; there is ac- cordingly scant evidence for speculation as to the manner of this evolution. As to the tim.e, we know only that microfossils representing nucleate organisms occur in the uppermost strata of the Proterozoic era. By making possible the precise transmission of a complicated heredity, the nucleus has made possible the development of complexities of structure and function exceed- ing by far anything occurring in non-nucleate organisms. It appears that as soon as the nucleus was in existence, organisms provided with it entered upon evolution in many characters and gave rise to many distinguishable groups. Among these groups, those which consist respectively of the typical plants and the typical animals are the greatest. There is, however, neither any a priori reason, nor any evidence from nature, for a belief that all groups of nucleate organisms must naturally belong to one or the other of these two. Several other groups, in general much less considerable than these, are thoroughly distinct and appear equally ancient. E. B. Copeland understood the history of life very much as it has just been pre- sented. In his teaching, he treated the bacteria and blue-green algae as standing en- tirely apart both from plants and from animals, and pointed out several other groups which are not as a matter of nature either plants or animals. It was his opinion that these groups should be treated as a series of minor kingdoms; he excused himself 4 ] The Classification of Lower Organisms from the attempt to formulate a definite and comprehensive system. This teaching was the original stimulus which has led to the present work. I bear witness that E. B. Copeland taught these things in 1914; he did not publish them until he had ceased to teach (1927). In the year 1926, when the teaching of elementary botany was first fully my own responsibility, I came to the conclusion that the establishment of several kingdoms of nucleate organisms in addition to plants and animals is not feasible; that all of these organisms are to be treated as one kingdom. This is one of the few points of originality which I claim for my work. It is true that the kingdom thus described is not very different from the third kingdom which various early authors proposed and which Haeckel (1866) named Protista. Haeckel, however, in his varied presentations of the kingdom Protista, included always the bacteria. By setting apart the bacteria and blue-green algae as yet another kingdom, one meets, at least in part, the objection to the "third kingdom" that it is heterogeneous beyond what can be tolerated. It has been necessary to meet also the objection that the "third kingdom" substi- tutes, for an acknowledgedly vague boundary between plants and animals, two vague boundaries: it has been necessary to recognize characters by which sharp definition can be given to plants and animals. It is my contention that these characters have long been known. The kingdom of plants, as the taxonomic representation of a natural group, is to be defined by the system of chloroplast pigments described by Willstatter and Stoll (1913), and also by the production of certain carbohydrates which occur only sporadically elsewhere. The kingdom of animals is defined by em- bryonic development through the stages called blastula and gastrula, as pointed out by Haeckel (1872). It is believed that no organisms exhibit both of these sets of characters; the "third kingdom" includes the nucleate organisms which exhibit neither. The kingdoms of plants and animals as here defined are essentially those which are traditionally and popularly accepted. They include all the creatures which Linnaeus listed as plants and animals, with the exceptions of forms of which he knew little, and which he listed superficially at the ends of his treatments of the respective kingdoms. Of course, the definitions are not warranted to describe the kingdoms without ex- ception. For one thing, each is supposed to have come into existence by evolution through a line of organisms which exhibited its characters imperfectly. For another, evolution can erase what it has created; it is proper to include in a group organisms which have by degeneration lost its formal characters. These things are true of all taxonomic groups. In due form, then, the system of kingdoms here maintained is as follows: Kingdom I. Mychota. Organisms without nuclei; the bacteria and blue-green algae. Kingdom II. Protoctista. Nucleate organisms not of the characters of plants and animals; the protozoa, the red and brown algae, and the fungi. Kingdom III. Plantae. Organisms in whose cells occur chloroplasts, being plastids of a bright green color, containing the pigments chlorophyll a, chlorophyll h, carotin, and xanthophyll, and no others; and which produce sucrose, true starch, and true cellulose. Kingdom IV. Animalia. Multicellular organisms which pass during development through the stages called blastula and gastrula; typically predatory, and accordingly consisting of unwalled cells and attaining high complexity of structure and function. This system has twice been given brief publication (1938, 1947). I am glad to say Introduction [ 5 that Barkley (1939, 1949) and Rothmaler (1948) maintain a system of kingdoms which differs from this in a single significant detail. Assuming that this system is tenable as a matter of reason, it will nevertheless not be accepted among taxonomists unless they have some knowledge of what it means in detail. No person is called upon to recognize the kingdoms Mychota and Protoc- tista until systems of their subordinate groups are available. The bulk of the present work consists of such systems. Complete systems of divisions or phyla, classes, and orders are presented. Groups of lower rank are presented in part, as examples. As a matter of facility, the groups of lower rank are presented more fully in the smaller or better known groups than in the larger or more obscure. The preparation of this work has taken more than ten years. In the course of it I have received much help. Among those who have answered queries, or who have in various drafts scrutinized the whole work or parts of it for faults of every degree of significance, are Dr. G. M. Smith of Stanford University; Dr. A. S. Campbell of St. Mary's College; Dr. Herbert Graham, formerly of Mills College; Dr. Lee Bonar, Dr. G. L. Papenfuss, and Dr. H. L. Mason of the University of California at Berkeley; Dr. E. R. Noble of the University of California at Santa Barbara; and Dr. H. C. Day of Sacramento Junior College. The counsel of E. B. Copeland has not been withheld. It is a matter of grief that two distinguished zoologists of the University of California, Dr. S. F. Light and Dr. Harold Kirby, have passed away during the long course of this work; as have two colleagues who were my closest friends, Dr. H. J. Child and Dr. C. C. Wright. The portrait of Haeckel which is my frontispiece is used by permission of Macrae Smith Company, Philadelphia. Two figures of Chrysocapsa are used by permission of the Cambridge University Press. Numerous figures have been taken from the Archiv filr Protistenkunde with the gracious permission of Prof. Dr. Max Hartmann. We do well to realize our indebtedness to libraries and librarians. To a great extent, this work has been made possible by the unstinted hospitality of the Biology Library of the University of California at Berkeley. Two statements appear regularly in prefaces; they are of truths which are strongly impressed upon authors. In the first place, those who have given help have made the work better; the author alone is responsible for deficiencies. The foregoing list of good friends and good scholars does not claim them as proponents of the thesis of this work. In the second place, the work is not offered as perfect or nearly so. The scholar in a strictly limited field may become master of the available knowledge. One who at- tempts studies in a broad field realizes that he is dealing with many subjects of which others know far more than he; that he has not wrung dry the existing literature; that some of the problems which puzzle him will be solved if he will wait a little longer. His colleagues have a right to raise these matters as criticisms. But surely, it is not desired that studies in broad fields be never attempted or indefinitely delayed. A matter which is particularly likely to arouse criticism is that of the names which are here applied to the groups. The principles according to which this has been done are set forth in the following chapter. I beg my colleagues, in dealing with this chapter and with the names subsequently applied, not to imagine that I have acted without grave thought. I have decided, that as in classification, so also in nomenclature, I should set before the community of biologists an experiment in the application of principles; among which principles there are surely some whose strict application will be to the good of our science. Chapter II AN ESSAY ON NOMENCLATURE Whoever sets forth a system of groups finds himself under the necessity of making responsible decisions as to names. The kingdoms have received more names than one (Table 1 ), and so have nearly all of the major groups within them: it has here been necessary to decide as to the validity and application of the names Flagellata and Mastigophora, Rhodophyceae and Florideae, Rhizopoda and Sarcodina, and many others. TABLE 1. Names Applied by Various Authors to the Kingdoms OF Systems of Four Kingdoms Authors Kingdoms Copeland, 1938, and Rothmaler, Copeland, Haeckel, 1894 Barkley, 1939 1948 1947 and here I Protophyta Monera Anucleobionta Mychota II Protozoa Protista Protobionta Protoctista III Metaphyta Plantae Cormobionta Plantae IV Metazoa Animalia Gastrobionta Animalia In dealing with plants, with animals, or with bacteria, it is necessary to observe the codes of nomenclature enacted by international congresses for the respective groups: the botanical code (Fournier, 1867; Lanjouw, 1952), with amendments enacted in 1954; the zoological code of 1889 as amended in 1948 and 1953 (issue of an edition incorporating the amendments is expected; Hemming, 1954); and the bacteriological code (Buchanan et al., 1948). Breach of the appropriate code renders an author liable to the penalty of having his work treated as nullity. The existence of three sets of rules for one thing, and the continual amendment of the older codes, are evidence of imperfection. It will not be purely destructive to point out certain anomalies in the codes as they stand. The zoological code pretends to overrule the principles of grammar in treating specific epithets as names. It is true that some of these words are names: the Catus in Felis Catus is a name of the cat, and the Mays in Zea Mays is a name of maize. But the great majority are adjectives; the sapiens in Homo sapiens is not by itself a des- ignation of man, and the vulgarc in Hordeum vulgarc is not a name of barley. It is a further offense against grammar that the code prescribes, as the names of all families of animals, adjectives in the feminine. Applied originally to families of birds, Aves, these names were unobjectionable; but the names of the kingdom and of the over- whelming majority of its subordinate groups are neuter. The botanical code as published with its appendages makes a book of more than two hundred pages. A statement of principles, in which the last clause provides for exceptions, occupies two pages. The definite rules and recommendations occupy about thirty-five pages; one who studies them critically will find that they prescribe more than one procedure not warranted by principle. A list of names maintained or rejected irrespective of principle occupies about seventy pages. These things mean that current botanical nomenclature is only within limits a matter of rule; it is to a considerable extent governed by enactments of the nature of ex post facto laws and bills of attainder. An Essay on Nomenclature [ 7 The bacteriological code is for the most part a condensation of an earlier edition of the botanical code. It includes the odd feature that the name of a genus of bacteria is to be changed if it had previously been used either among plants or among Protozoa. Since there is an earlier Phytomonas among flagellates, bacteriologists have given a new name to the bacterium Phytomonas. The avoidance of homonyms which they desire will not, however, be attained: no zoologist will allow a new name for the flagellate Klebsiella on account of an earlier Klebsiella among bacteria. The grounds upon which these things are treated as wrong are provided by a passage in the botanical laws of 1867 which is believed to define the legitimate authority of congresses and codes: "Les regies de la nomenclature ne pouvent etre ni arbitraires ni imposees. Elles doivent etre bassees sur des motifs assez clairs et assez forts pour que chacun les comprenne et soit dispose a les accepter." It is implied by this statement that principles, appealing to the reason and found sound by the trial of experience, were in existence when it was written; and this is the truth. By this statement, the legitimate powers of congresses are those of courts of common law, which avoid the explicit making of law, but discover the law, inter- pret it, and apply it. Congresses and codes may legitimately (a) state explicitly corollaries of the principles when they are not obvious; and (b) determine arbitrarily matters which are necessarily determined arbitrarily, not being within the range of principle. One would not in theory deny a power (c) to validate breaches of principle when these are of an expedience verging on necessity; but its use by botanical con- gresses to produce a roll of exceptions of twice the bulk of the text of the code leads one to doubt the expedience of this admission. It has been through failure to recog- nize the legitimate limits of their powers — through a conception that their powers are sovereign or plenary — that international congresses have come to enact codes conflicting with each other and giving incomplete satisfaction in themselves. Under these circumstances, a nomenclature of superior legitimacy can be applied in groups treated as removed from the jurisdiction of the codes. Not without diffi- dence, this assumption is extended to the bacteria; it will be agreed that the nomen- clatural practice applied to the bacteria must be the same as that which is applied to the blue-green algae. Here one attempts a brief formulation of those principles, appealing to reason and proven sound in practice, to which all nomenclature must conform. 1. Scientific names are words of the Latin language. They are not "of Latin form" or "construed as Latin"; they are Latin. This is to treat Latin as a living language and scientific names as subject to the rules of its grammar. They are not code-designa- tions, nor words of any language or none, as chemical names are. 2. The name of a group of the kind called a genus is a proper noun in the singular. Linnaeus replaced all generic names which were adjectives; all of us his successors should do likewise. 3. The names of groups of genera are proper nouns, or adjectives used as proper nouns, in the plural. The foregoing principles are of pre-Linnaean origin; beginning with his first sig- nificant work (1735), Linnaeus took them for granted. For the principle next to be stated, authority is the practice of Linnaeus in later works (1753 and subsequently) : 4. The name of a species consists of the name of the genus to which it belongs fol- lowed by one epithet, ordinarily an adjective, occasionally a noun in apposition or in the genitive. 8 ] The Classification of Lower Organisms A fifth principle represents Linnaean practices as subsequently modified: 5. Named taxonomic groups are necessarily of certain fixed ranks called categories, i.e., lists. There are seven principal categories, specified as follows. Every individual organism belongs to a group conceived as the single kind and called a species. Every species belongs to a genus; every genus to a family; every family to an order; every order to a class; every class to a division or phylum; ever)' division or phylum to a kingdom. These conventions have the effect that the groups of each principal category embrace the entire range of the kinds of organisms. The categories of genera and species come down from classic antiquity. Linnaeus originated orders; he originated classes in the sense of named definite groups; and it appears that he is responsible for kingdoms: the writer knows of no earlier authority for the traditional three kingdoms of nature. The category next below that of king- doms has been variously called; originally it was emhranchements (Cuvier, 1812). The history of the category of families is somewhat involved. It originated in the work of Adanson (1763); in the following year, Linnaeus (1764) treated the groups which Adanson had called families as natural orders. Botanists for a long time held that families and orders are the same thing. Zoological practice gradually made fam- ilies a separate category. Authority for the list of seven principal categories as given is Agassiz (1857). Nothing prevents the assignment of groups to categories other than these, to sub- classes, tribes, and the like. These may be called subordinate categories. The groups of any subordinate category embrace only fragments of the range of kinds of organisms. The work of Linnaeus was largely innovation, and he did not have the face to de- clare binding the generally accepted rule of priority. Definite authority for the rule is de Candolle (1813). As currently applied, it may be stated as follows: 6. The valid name of a group is its oldest published name, conforming to the rules, and not previously applied in the same kingdom. As corollaries of the rule of priority, when groups are combined, the oldest name of any of them must be applied to the whole, and when a group is divided, its name must be retained for one of the parts. The part to which the original name is to be applied is determined by the method of types, formulated by Strickland and his as- sociates (1843) : 7. When a group is divided, its name must be applied to the portion which includes whatever part of it the original author would have regarded as typical. The part thus specified is the nomcnclatural type of the group. In the application of these principles to the naming of the groups of Mychota and Protoctista, the following practices appear expedient. A name is applied by publication in such fashion that the community of biologists may reasonably be held responsible for knowing of its existence and recognizing the entity to which it is to be applied. This means that it is to be printed in a technical book or journal and defined in a language for which the generality of biologists will not require an interpreter, namely Latin, English, French, or German. Any regulation more detailed than this is an excuse for breaches of priority. Definition is not neces- sarily by description: nearly all of the Linnaean genera of plants were established by the listing of species in the Species Plantarum. When two or more groups published in the same work at the same time are to be combined, their names are of equal priority. The choice of one of their names by the first author who combines them is binding. An Essay on Nomenclature [ 9 A type as specified in the original publication of a group, or as implied by the in- clusion of a single subordinate group, is unchangeable. Linnaeus and his immediate successors had no conception of the device of types, and it is practically impossible to be certain of the elements which they would have regarded as typical in some of their groups. It remains necessary that the type system be applied to these groups. In some of them, it may be expedient that international authority, proceeding with due caution, declare types arbitrarily. An individual scholar will do better to call what he supposes to be the type of a group by a difTerent term, namely standard (Sprague, 1926) : the standard of a group is a supposed type which remains open to debate. The framers of codes have undertaken to make binding the choice of a type by the first author who divides a group. On various occasions, however, this action has been demonstrably mistaken. Certain venerable names, as Vermes and Algae as used by Linnaeus, were applied to altogether miscellaneous collections of organisms among which the selection of a standard would be purely arbitrary. Such names are called nomina confusa, and are to be abandoned. It follows from the principle of the binomial nomenclature of species that no genus is named until one or more of its species are designated by binomial names. It fol- lows also that in works in which the nomenclature of species is not definitely binomial no names are of any standing. Hence, the point of time from which priority is effective is that of the introduction of binomial nomenclature, namely 1753. The enactment of other starting points for the nomenclature of particular groups is pretended law which is not law, like the pretended laws of American states which attempt to regu- late interstate commerce under the appearance of doing something else. The original spelling of names, so far as it is tolerable Latin, is not to be changed. Errors of gender or number, obvious mistakes of spelling, and misprints, are to be corrected. Good Latin is written without diacritical marks: a German Umlaut in a name as published is corrected by inserting an e; accents, cedilles, and other barbar- isms are dropped. The codes err in prescribing changes in spelling beyond those which are here admitted. If they should establish uniformity in the future, it would be at the expense of divergence from the most respected works of the past. Specific epithets are capitalized if they are ( 1 ) names in the nominative, in ap- position with the generic names; (2) names of persons, places, or organisms in the genitive; (3) adjectives derived from names of persons. Transfer of groups from one kingdom to another does not warrant any meddling with names. When a group is transferred from one kingdom to another, its valid name in the former — its oldest name not previously used in the kingdom in which it was originally published — has priority from the date of its original publication. Names of groups higher than genera are in the plural. Some are proper nouns; the remainder are adjectives used as proper nouns, agreeing in gender with the names of the kingdoms in which they are included; either expressing characters of the groups which they designate, or consisting of generic names modified by terminations signi- fying "resembling" or "of the group of." Plurals of generic names are not tenable (de Candolle, 1813) : Ericae means the species of the genus Erica; it does not mean, and can not be used to designate, the genus together with its allies. Names consisting of words other than generic names modified by terminations signifying "resembling" or "of the group of" are not tenable, because they are nonsense: the name Conifer- inae, applied by Engler to a class, is an adjective with an additional adjectival termi- nation superimposed. 10 ] The Classification of Lower Organisms A name once applied in any principal category may not be transferred to another, unless it be of a form barred in the former and prescribed in the latter. The main clause of this statement is a consequence of the rule of priority. The exception is a concession to the practice of using names with uniform endings in certain categories. Names of groups not of principal categories do not have priority as against names applied in principal categories. This practice, which denies to names in subordinate categories the full sanction of priority, is justified by the fact that groups in these cate- gories are of concern only to specialists in the groups in which they occur; one is not in reason responsible for being aware of their names in groups outside of ones own specialty. Almost all families of plants have had names with the uniform ending -aceae from the point of time at which the category of families was distinguished from that of orders. Such names were applied to algae, liverworts, and mosses by Rabenhorst (1863) and to higher plants by Braun (in Ascherson, 1864). They are adjectives in the feminine, agreeing with the name of the kingdom Plantae. It is altogether expe- dient that names of this form be held obligatory throughout the kingdom of plants. A uniform termination for names of families of animals has been in use for many years, but these names are not equally positively sound both grammatically and by priority. There has been a strong tendency to apply uniform terminations to the names of groups of other categories. So far as concerns groups of subordinate categories — suborders, subfamilies, and so forth — this practice appears expedient; these groups being of concern only to experts in the groups in which they occur, it is as well that their designations be of the nature of code designations rather than names. In at- tempting to put this practice into effect, some zoologists have made the mistake of applying the same adjective in different genders to different groups; they have not realized that Amoebida is the same word as Amoebidae. Meanwhile, uniform termi- nations for names of phyla, classes, and orders, beside involving wholesale violation of priority, is something of an insult to the intelligence. The terminations of ordinal names in -ales and of family names in -aceae, currently in use among the Mychota, are here changed to -alea and -acea to agree with the neuter name of the kingdom. A change of the gender of an adjective does not create a new word, and the original authorities for the names will stand. Accordingly: The name of an order of Mychota, if based on that of a genus, must bear the termi- nation -alea. Names of this form are valid in no other category of this kingdom, and may be reapplied to orders. They have priority and authority by publication explicitly as orders. Such names do not supersede older ordinal names not based on names of genera. The name of a family of Mychota is formed of the stem of a generic name (not necessarily a valid name, but never a later homonym) by adding the termination -acea. Names of this form are not valid in any other categor)', and may be reapplied to families. They have priority and authority by publication explicitly as families. The names of families of Protoctista, unlike those of Mychota, of plants, and of animals, do not have by priority prevalently a uniform termination. Many of the oldest were first named in -ina. Those of flagellates and myxomycetes have double sets of names, respectively in -aceae and -idae, in current use. It is not expedient to impose uniform terminations on the names of these groups, at least not in the present work. Accordingly: Each group of Protoctista is called by its oldest name of tenable form in the cor- rect category, barring any previously used in other principal categories, irrespective An Essay on Nomenclature [ 1 1 of termination. All names which are adjectives are used in the neuter, but ascribed to the original authors. The practices described have resulted in the use of many names which will seem strange, producing lists which are undeniably heterogeneous. A friendly critic notes as an example of these things the Hst of classes, Heterokonta, Bacillariacea, Oomy- cetes, and Melanophycea, on page 55. It will be realized that the three among these names which are adjectives must be in the feminine if the groups are construed as Plantae, neuter if Protoctista. Taking this fact into account, these are actually the first names, not previously used in other principal categories, applied to these groups as classes. What other names could one use? Everyone will know what groups are intended. Would any person understand them better if new names had been created by applying a uniform termination to the old roots? Enough about nomenclature. We should begin to deal with organisms. Chapter III KINGDOM MYCHOTA Kingdom I. MYCHOTA Enderlein Stamm Moneres Haeckel Gen. Morph. 2: xxii ( 1866), in part. ScHizoPHYTAE Cohn in Beitr. Biol. Pfl. 1, Heft 3: 201 (1875). Class ScHizoPHYTA or Protophyta McNab in Jour, of Bot. 15 : 340 ( 1877 ) ; not sec- tion Protophyta nor cohors Protophyta Endlicher (1836). Kingdoms Protophyta and Protozoa Haeckel Syst. Phylog. 1: 90 (1894), in part; not Protophyta Endlicher nor class Protozoa Goldfuss (1818). Subdivision Schizophyta Engler in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. la: iii (1900). Division Schizophyta Wettstein Handb. Syst. Bot. 1 : 56 ( 1901 ). Phylum Protophyta Schaffner in Ohio Naturalist 9: 446 (1909), in part. Kingdom Mychota Enderlein Bakt.-Cyclog. 236 (1925). Kingdom Monera Copeland f. in Quart. Rev. Biol. 13: 385 (1938). Kingdom Anucleobionta Rothmaler in Biol. Zentralbl. 67: 248 (1948). Organisms without nuclei. The common name of Mychota in general is bacteria, but those which contain chlorophyll together with other pigments which make the green color impure are called blue-green algae. The cells of Mychota are always separate or physiologically independent: multi- cellular bodies with distinct tissues do not occur. The cells are of various shapes; most often they are cylindrical, being of diameters from a fraction of one micron to a few microns, rarely more. Except in the groups of myxobacteria and spirochaets, they are walled; the thickness of the walls is of the order of 0.02^ (Knasyi, 1944). The walls may contain cellulose, but consist chiefly of pectates, compounds of slightly oxidized polysaccharides with sulfate, calcium, and magnesium (Kylin, 1943). These compounds are readily rendered gelatinous by hydration or hydrolysis, and the cells are often imbedded in gelatinous layers called sheaths or capsules. In describing the Mychota as lacking nuclei, one commits himself to one side of a controversy of many years duration. Because of the greater size of the cells of the blue-green algae, the facts are more easily ascertained in this group than in the proper bacteria. The cells of blue-green algae (Gardner, 1906; Swellengrebel, 1910; Haupt, 1923) are divided into outer and inner parts which are not sharply distinct. Pigments occur in a dissolved or colloidal condition in the outer part, which contains also granules of stored food. The granules are not carbohydrate, although a form of glycogen dis- tinct from that of higher organisms has been extracted (Gardner; Kylin, 1943). The inner part contains rods and granules, some of which stain like chromatin, while others ("red granules of Biitschli") are stained red by methylene blue. Cell division is by constriction. Olive (1904) interpreted the inner part of the cell as a nucleus continually in process of mitosis, and accordingly without a membrane. It is true that in series of disk-shaped cells one may recognize series of corresponding granules. Where the cells are more elongate, the rods and granules of the interior are divided at random. Haupt expressed the impropriety of calling any part of these cells a nucleus. Kingdom Mychota [13 Recent studies of typical bacteria by conventional microtechnical methods (Rob- inow, 1942, 1949; Tulasne and Vendrely, 1947) and by the electron microscope (Hil- lier, Mudd, and Smith, 1949) have made it possible to recognize the essential identity of the structure of their cells with those of the blue-green algae. The protoplast con- sists of outer and inner parts. The outer part, considered as a substance, may be called ectoplasm (Knasyi, 1930), and the inner, considered as a body, may be called the central body (Biitschli, 1890). The ectoplasm is very thin, occupying usually less than one fifth of the radius of the cell. The spiral bands which have often been seen % Bi^i Ss;.- Z# )ii-i'- "ji;-^ Irx •■■•;i©\ ^-> '■l-i" V ^ .?.. ■fw .^,.'^» ■; ^vWfe ■4 m Fig. 1.- — Structure of cells of blue-green algae, a, Symploca Muscorum after Gardner (1906). b, Oscillatoria Princeps after Olive (1904). C, Lyngbya sp. from a slide prepared by Dr. P. Maheshwari, x 1,000. d, Anabacna circinnalis after Haupt (1923) x 2,000. in cells of bacteria, and which Swellengrebel ( 1906) mistook for a nucleus, are thick- enings of the ectoplasm. Specific stains for nucleoprotein (chromatin), as Feulgen or Giemsa, usually color uniformly the entire central body. If the cells are exposed to hydrochloric acid, a part of the nucleoprotein, containing ribonucleic acid, dissolves. The remainder, containing desoxyribonucleic acid, persists in the form, basically, of a single fairly large granule in each cell. In rod-shaped bacteria, this granule appears usually to divide by constriction before the cell begins to divide, and may redivide, so that the cell may contain two dumb-bell shaped bodies. De Lamater and Hunter (1951) succeeded in a partial de-staining of the dumb-bell shaped bodies and inter- preted them as dividing nuclei containing centrosomes and definite numbers of chromosomes; typical chromosomes, however, are never as small as the bodies they describe, and are not imbedded in bodies of nucleoprotein from which they can be distinguished only by the most refined technique. Enderlein (1916) observed in rod- shaped bacteria series of granules of which some at least are identical with the dumb- 14 ] The Classification of Lower Organisms bell shaped bodies. He named these granules mychits. It might be held that the mychit is a chromosome, and the central body of bacteria a nucleus of a single chromosome, if it were not true that the blue-green algae contain comparable bodies of variable form and indefinite number. Many bacteria swim by means of flagella. The diameter of the flagella, as revealed by the electron microscope, is of the order of 0.02 [J.. Their positions and lengths were made known, before the invention of the electron microscope, by the technique of Loeffler (1889), which consists essentially of depositing upon them a heavy layer of tannic acid. By the absence or presence and arrangement of flagella, bacteria are classified as of four types: atrichous, without flagella; monotrichous, with one flagel- lum at one end; lophotrichous, with a tuft of flagella at one end; peritrichous, with flagella on the sides. Myxobacteria, spirochaets, and such blue-green algae as are sheathless filaments, are capable of bending movements (some spirochaets, observed with the electron microscope, are found also to have flagella at the ends of the cells). Spirochaets swim vigorously; in myxobacteria and blue-green algae, the bending movements are a mat- ter of slow writhing. Filaments and cells of blue-green algae are capable also of a moderately rapid gliding movement. The mechanism of this movement has been the subject of much speculation, reviewed by Burkholder ( 1934), but remains uncer- tain. The appearance of the movement is as though it were caused by local secretion of substances affecting surface tension. The normal reproduction of Mychota is by constriction of the cells, each into two equal daughter cells; whence the various names in schizo- (Greek axi^co, to split). Henrici (1928) studied the changes undergone by bacteria during multiplication. As the cells become numerous, decreasing the food supply and producing substances harmful to themselves, they begin to attain greater length before dividing. Subse- quently there is a gradual transition to enlarged and distorted forms called involution forms, which divide irregularly, cutting off minute fragments. These observations suggest the idea that the involution forms are the true normal forms of bacteria, the so-called normal forms being a temporary stage adapted to rapid multiplication under favorable conditions. In many rod-shaped bacteria, when conditions cease to be ideal, the protoplasts produce within themselves walled bodies of dehydrated protoplasm called spores (endospores). In general, each cell produces only one spore. No experiment has definitely shown how long these spores can remain alive; it is surely a matter of cen- turies, doubtfully of millenia. Lohnis and Smith (1916, 1923) observed of Azotobactcr that numbers of proto- plasts might escape from their walls and unite in a common mass, which they named the symplasm. The existence of this stage has never been confirmed by other authori- ties. If the symplasm exists, it is a device for achieving the effect which nucleate or- ganisms attain by sexual reproduction, that is, combination of the heredity of differ- ent lines of ancestry. Tliat Mychota can actually combine characters from different linos of ancestry was first demonstrated beyond question by Tatum and Ledcrberg (1947). They mixed cultures of pairs of varieties of Escherichia coli, differing in two or more physiological characters, and isolated from the mixtures races having characters de- rived from both components. Further Mork, reviewed by Ledcrberg and Tatum (1953), has abundantly demonstrated phenomena analogous to typical sexual reproduction. Kingdom Myrhola [15 '9^ ^ V* ••% ^ ^ ^^ m^ W 9m w% #^., li.^ Fig. 2. — Photographs of Escherichia coli by Dr. C. F. Robinow, reproduced by Hillier, Mudd, and Smith (1949); left, stained to show the ectoplasm, in which there are thickenings which tend to be spiral; right, stained to show the large re- peatedly dividing granule in the central body. About x 2,000. By courtesy of Dr. Robinow and of the Society of .\merican Bacteriologists. Kingdom Mychota [17 The metabolic systems of the Mychota are remarkably diverse. The most super- ficial list of physiological types would include the following: (a) anaerobic parasites and saprophytes; (b) facultatively aerobic parasites and saprophytes; (c) the vinegar bacteria, being apparently the only known organisms which, while requiring organic matter, are incapable of anaerobic energesis; (d) the autotrophic bacteria, the only organisms which maintain life by oxidation of inorganic matter; (e) organisms living by incomplete photosynthesis; and (f) organisms capable of typical photosynthesis. Geologically, the Mychota are ancient. Iron deposits and certain other formations believed to have been produced by them occur in Archeozoic rocks estimated as more than a billion years old. More than five thousand names have been applied to species of bacteria, but in the attempt to distinguish them, only about fifteen hundred are enumerated (Ber- gey's Manual, 6th ed., 1948). The species of blue-green algae are probably fewer than one thousand. The classification of this group is inescapably highly tentative. The morphology is simple and not highly varied; the physiological characters likewise appear simple, but are highly varied, including many which are not known in other groups. The antiquity of the Mychota makes it probable that many groups which appear to be- long together consist actually of parallel developments. The undoubted antiquity of the apparent main groups would lead one to place them in the category of divisions or phyla; but it is not expedient to make many divisions of a group of 2500 species: this would produce too many divisions of a single class or classes of a single order. The kingdom is accordingly treated as a single phylum, and its main divisions as classes. Phylum ARCHEZOA Haeckel yhylB. Archephyta and Archezoa Haeckel Syst. Phylog. 1:90 (1894); not Phylum Archephyta Haeckel (1866). Phylum Myxophyceae Bessey in Univ. Nebraska Studies 7: 279 (1907). Phyla Dimychota and Monomychota Enderlein Bakt.-Cyclog. 236 (1925). Bacteriophyta and Cyanophyta Steinecke (1931). Stamme Cyanophyta and Schizomycophyta Pascher in Beih. bot. Centralbl. 48, Abt. 2: 330 (1931). Divisions Cyanophyta and Schizomycetae Stanier and van Niel in Jour. Bact. 42: 464 (1941). Characters of the kingdom. Archezoa is Haeckel's name, at the point cited, for the bacteria. The name had been applied othervv^ise by Perty (1852), but not in a principal category. It will not be considered inappropriate, if it be remembered that the meaning of zoe is as much life as animal. The conventional division of the group into two classes, bacteria and blue-green algae, is not perfectly natural. All of the recognized blue-green algae belong together; but the recognized bacteria are a wide miscellany, some of them belonging with the blue-green algae. Here three classes are recognized. 1. Cells without internal pigment, heterotrophic or living by chemosynthesis; not usually pro- ducing filaments with prominent sheaths. 18 ] The Classification of Lower Organisms 2. Cells with firm walls, non-motile or motile by means of flagella Class 1. Schizophyta. 2. Cells with thin walls or none, motile by means of changes of shape, also some- times by flagella Class 2. Myxoschizomycetes. 1. Cells mostly with internal pigment, living by photosynthesis or chemosynthesis, exception- ally heterotrophic; often producing filaments with prominent sheaths Class 3. Archiplastidea. Class 1. SCHIZOPHYTA (Cohn) McNab Schizomycetes Nageli ex Caspary in Bot. Zeit. 15: 760 (1857). Class Schizophyta or Protophyta McNab in Jour, of Bot. 15: 340 (1877). Class Schizomycetes Winter in Rabenhorst Kryptog.-Fl. Deutschland 1, Abt, 1: 33 (1879). Class Schizomycetae SchafTncr in Ohio Naturalist 9: 447 (1909). Classes Holocyclomor pha and Hemicyclomorpha Enderlein Bakt.-Cyclog. 236 (1925). Dependent or chemosynthetic Mychota, with walled cells, without photosynthetic pigments and not producing sheathed filaments. This class includes as orders the typical bacteria and two minor groups. 1. Cells solitary or loosely gathered into clusters or filaments, spherical, rod-shaped, or spiral, not differentiated along the axis Order 1. Schizosporea. 1. Consisting of branched filaments not divided into cells Order 2. Actinomycetalea. 1. Cells attached by stalks, the attached and free ends differentiated Order 3. Caulobacterialea. Order 1. Schizosporea [Schizosporeae] Cohn in Hedwigia 11: 17 (1872). Order Schizomycetes (Nageli) McNab in Jour, of Bot. 15: 340 (1877). Order Eubacteria Schroter 1886. Order Haplobacteriacei Fischer in Jahrb. wiss. Bot. 27: 139 (1895). Orders Cephalotrichinae and Peritrichinae Orla-Jensen in Centralbl. Bkt. Abt. 2,22: 334,344 (1909). Order Eubacteriales Buchanan in Jour. Bact. 2: 162 (1917). Mychota whose cells in the typical condition are without internal pigment, walled, of the form of rods, spheres, or spirals, not differentiated along the axis. As this is a numerous group, likely with advancing knowledge to require division, it will be well to provide it with a nomenclatural standard, and to suggest as such Cohn's principal discovery among bacteria, namely Bacillus sublilis. These are the typical bacteria. As originally described by Leeuwcnhoeck (1677), they were taken to be a few kinds of "animacules" distinguished only by extremely small size. Only after many years were they shown to be numerous and varied, and highly important as causes of diseases and of other natural phenomena. The natural classification of the typical bacteria has been hard to discern. The characters by which groups can be distinguished include forms of cells and of clusters of cells; absence or presence and arrangement of flagella; non-formation or formation Kingdom My c hot a [ 19 of endospores; metabolic products; and the peculiar character called Gram reaction. The method of staining invented by Gram, 1884, consists of staining successively with gentian violet and iodine. It gives an intense blue-black color. From some bac- teria, this color is washed out by alcohol; others retain it; the former are said to be Gram negative, the latter Gram positive. In practice one applies successively gentian violet, iodine, alcohol, and safranine, the last being a red dye whose function is to make the Gram negative bacteria visible. The substance stained by gentian violet plus iodine is believed to be lipoid, such as occurs in all cells. The Gram positive quality is believed to consist in a relatively low isoelectric point, a capacity, that is, to combine with anions in a relatively acid medium. This quality lies in the ectoplasm of the cells and disappears in aging cultures. The classification given in Bergey's Manual (1923, 1925, 1930, 1934, 1939, 1948) is accepted (at least among Americans) as standard. The following system of thirteen families is a moderate rearrangement of the Bergeyan system, with certain ideas or names from Enderlein (1917, 1925), Buchanan ( 1925), Pribram (1929) and Stanier andvanNiel (1941). 1. Gram positive, with exceptions many of which are intracellular parasites; atrichous or peritrichous. 2. Spheres dividing in more planes than one. 3. Gram positive Family 1. Micrococcacea. 3. Gram negative; intracellular patho- gens in animals Family 2. Neisseriacea. 2. Rods, or spheres dividing in one plane. 3. Not producing endospores. 4. Atrichous. 5. Not intracellular parasites. . Family 3. Corynebacteriacea. 5. Intracellular parasites Family 4. Rickettsiacea. 4. Peritrichous Family 5. Kurthiacea . 3. Producing endospores Family 6. Bacillacea. 1. Gram negative. 2. Atrichous or peritrichous, requiring com- paratively complicated organic food. 3. Not plant pathogens. 4. Not fixing nitrogen. 5. Capable of growth on or- dinary media Family 7. Achromobacteriacea. 5. Requiring special media; minute atrichous pathogens. Family 8. Pasteurellacea. 4. Fixing nitrogen Family 10. Azotobacteriacea. 3. Plant pathogens Family 9. Rhizobiacea. 2. Atrichous, monotrichous, or lophotrich- ous; the atrichous representatives, and many others, can survive with organic foods simpler than carbohydrates, or with none. 3. Mostly requiring at least carbo- hydrates Family 11. Spirillacea. 20 ] The Classification of Lower Organisms 3. Not requiring carbohydrates. 4. Oxidizing alcohol to acetic acid, and acetic acid to CO2 and H2O Family 12. Acetobacteriacea. 4. Not as above; many examples strictly autotrophic Family 13. Nitrobagteriacea. Family 1. Micrococcacea [Micrococcaceae] Pribram in Jour. Bact. 18: 370, 385 (1929). Family Coccaceae Zopf 1884; but the genus Coccus is a scale insect. Gram positive spheres producing packets or irregular masses. Micrococcus, saprophytic or parasitic, producing irregular masses of cells; the pathogenic species have been treated as a separate genus Staphylococcus. Sarcina, saprophytic or commensal spheres pro- ducing packets. Family 2. Neisseriacea [Neisseriaceae] Prevot ex Bergey et al. Manual ed. 5 : 278 (1938). Family Neisseriacees Prevot in Ann. Sci. Nat. Bot. ser. 10, 15: 119 (1933). Obligate parasites, the Gram negative spherical cells occurring chiefly in pairs within leucocytes in the lesions of disease. Neisseria gonorrhoeae, the gonococcus; A^. ]Veich- selbaumii Trevisan {N. intracellularis, N. meningitidis, Auctt.), the meningococcus. Family 3. Corynebacteriacea [Corynebacteriaceae] Lehmann and Neumann 1907. Family Corynebacteriidae Enderlein in Sitzber. Gess. naturf. Freunde Berlin (1917) : 314. Family Lactobacillaceae Winslow et al. in Jour. Bact. 2: 561 (1917). Family Lactobacteriaceae Orla-Jensen 1921. Family Leptotrichaceae Pribram in Jour. Bact. 18: 372 (1929), not family Leptotrichacei Schroter 1886. Gram positive rods, or spheres dividing in one plane and producing chains, non-motile. Streptococcus, spheres in chains; saprophytes in milk, involved in the making of butter and cheese; and commensals and serious pathogens causing, for example, abscesses, septicemia, erysipelas, and pneumonia. Diplococcus, spheres usually in pairs, encapsulated. D. pneumoniae occurs in many immunologically distinct races which are the usual causes of pneumonia. Lactobacillus, rods, microaerophilic, producing lactic acid. In milk, involved in the making of butter and cheese; in the oral cavity, being the usual agent of dental caries (Rosebury, Linton, and Buchbinder, 1929); common in sewage. Leptotrichia, rods which become exceptionally long before dividing. Oral cavity of man and beasts. Corynebacterium, rods, becoming club-shaped, staining in a banded pattern. The type species is the agent of diphtheria, C. diphthcriae; the genus includes also many harmless commensals important only as making diagnosis difficult. The cells divide in an exceptional fashion, by breaking violently from one side to the other near one end; the cut-off end swings around beside the main body and proceeds to grow. Repeated division in this manner produces clusters of parallel cells (Park, \V'iliiams, and Krumweide, 1924). Family 4. Rickettsiacea [Rickettsiaceae] Pinkerton 1936. Families Bartonellaceae Gieszszykiewicz 1939 and Chlamydozoaceae Moshkovsky 1945. Minute obligate intra- cellular parasites of varied form, commonly Gram negative but with Gram positive granules. There have been many observations of bodies of the characters stated, but a satis- factory classification of them is not yet possible. Howard Taylor Ricketts showed that Rocky Mountain spotted fever is transmitted by the tick Dcrmocentor, and observed, in the cells of diseased tissues, minute irregularly staining bodies; in 1910, Kingdo7n Mychota [21 in the course of further studies of the disease, he contracted it and died. Stanislas Prowazek, called into the Austrian military medical service in 1914, began to study typhus, which is transmitted by lice; observed similar intracellular bodies; contracted typhus, and died in February, 1915 (Hartmann, 1915). The cause of Rocky Mountain spotted fever is Rickettsia Rickettsii, and that of typhus. is R. Prowazekii. Several other species are known. By serological methods, Anigstein (1927) showed that R. Melophagi is closely related to Corynebacterium. In cases of the disease of the west slope of the Andes called verruga peruana, Oroya Fever, or Carrion's disease, there occur intracellular bodies named Bartonella bacillijormis. Noguchi and others (192H) completed the demonstration that the disease is transmitted by biting flies of the genus Phlebotoyniis. Good authority has construed Bartonella as a sporozoan. Students of flagellates, Sarkodina, and Infusoria have occasionally observed in the cytoplasm or nuclei of these organisms minute bodies multiplying to form consid- erable masses. These parasites have generally been construed as chytrids, but have little in common with proper chytrids. The genus Caryococcus Dangeard includes at least a part of them. Family 5. Kurthiacea, fam. nov. Gram positive peritrichous rods, not producing endospores. Kurthia, harmless; Listeria Pirie ex Murray in Bergey's Manual 6th ed. 408 (1948), pathogenic in sheep and man. Family 6. BaciUacea [Bacillacei] Fischer in Jahrb. wiss. Bot. 27: 139 (1895). The spore-forming rods, always Gram positive, mostly peritrichous, very numerous in species, common, and important. Bacillus Cohn 1872, is one of the oldest generic names of rod-shaped bacteria which can be definitely applied: it can be definitely applied because the type species B. subtilis was so described as to be recognizable. The genus has been used to include rods in general or at random. Defined as aerobic spore-formers, as proposed by Buchanan, 1917, it is a thoroughly natural group. As treated in the fifth edition of Bergey's Manual, it included nearly 150 duly distinguished species; in the sixth edition, this number is cut to thirty-three. The great majority are saprophytic. Ex- ceptions, important pathogens, are B. anthracis; and B. alvei and other species causing foulbrood of bees. The anaerobic spore-formers constitute the genus Clostridium. The type species wa? discovered and named three times in different connections. As an anaerobe involved in the fermentations which give butter its flavor, it is C. butyricum Prazmow- ski. As an organisms whose cells contain granules staining like starch, it is Bacillus Amylobacter van Tieghem. It has the property of fixing nitrogen; discovered in this capacity by Winogradsky (1902) it was named C. Pastorianum. The species of Clostridium, as of Bacillus, are numerous. They are primarily saprophytic, but many species produce powerful toxins and are serious pathogens. Examples are C. tetani; C. botulinum; and C. septicum and a whole roll of other species, causing various forms of gangrene, occasion for the study and distinction of which was found during World War I. Family 7. Achromobacteriacea [Achromobacteriaceae] Breed 1945. Family Bac- teriaceae McNab in Jour, of Bot. 15: 340 (1877), based on a generic name which must be abandoned as a nomen conjusum. Family Enterobacteriaceae Rahn 1937, not based on a generic name. Gram negative rods which lack the dictinctive characters of the families subsequently to be treated. 22 ] The Classification of Lower Organisms The nine genera listed first occur normally in animals, mostly in the gut and mostly as commensals; exceptions are important pathogens. Most of them produce acid, and many of them produce gas, from sugar. These genera are the traditional colon-typhoid-dysentery group. Escherichia coli, the colon bacillus, and Aerohacter aerogenes, the gas bacillus, are common commensals which produce acid and gas from dextrose and lactose. The standard method of testing waters for contamination is essentially a test for the presence of these organisms. Klebsiella also produces acid and gas from sugars. It inhabits the respiratory tract. The cells are heavily capsulated and non-motile. The type species K. pneumo- niae is an important pathogen, the pneumobacillus of Friedlander. Proteus vulgaris (this is at least the third genus to bear the name Proteus, but the first in this kingdom) produces acid and gas from dextrose but not lactose, and liquefies gelatine. It is usually isolated from spoiled meat. Salmonella is distinguished from Proteus by non-liquefaction of gelatine. Many of its species are harmless commensals; others cause paratyphoid fevers. Immunologi- cal study of cultures of Salmonella from cases of disease and from waters have re- sulted in the distinction of fully 150 races, mostly unnamed and identifiable only by immunological reactions. Eberthella includes motile rods producing acid but not gas from sugars, and belonging to the same immunological system as the various races of Salmonella. Eberthella typhi causes typhoid fever. Shigella is distinguished from Eberthella by non-motility. The Shiga bacillus, S. dystenteriae, is the cause of dystentery. Bacteroides is a numerous group of acid-producing gut bacteria, motile or non- motile, generally harmless.^ distinguished from the foregoing as strictly anaerobic. Alcaligenes fecalis, an apparently harmless organism isolated from intestinal con- tents, does not produce acid from sugars; grown in milk, it produces an alkaline reaction. Numerous races of bacteria which have been isolated from soil and are capable of attacking cellulose are assigned to the genus Cellulomonas. Bacteria which produce an extracellular red pigment are Serratia (one of the oldest generic names for bac- teria); those which produce yellow pigment are Flavobacterium; those which produce blue, black, or violet growths are Chromobacterium. Cultures which lack the distinc- tive characters of all of the above named genera (most such cultures have been isolated from water) are called Achromohacter. Family 8. Pasteurellacea nom. nov. Family Parvobacteriaceae Rahn; there is no corresponding generic name. Minute non-motile Gram negative rods, pathogenic, requiring special media for cultivation. Pasteurclla avicida is the cause of chicken cholera, upon which Pasteur made important studies. Of greater direct importance to man is Pasteurella pestis, the cause of plague. Hemophilus includes the agents of whooping cough, soft chancre, and conjunctivitis. Brucella includes the organisms which cause Malta fever, undulant fever. Bang's disease, contagious abortion. Pfeif- ferella mallei is the cause of glanders. Family 9. Rhizobiacea [Rhizobiaceae] Conn in Jour. Bact. 36: 321 (1938). Gram negative rods, atrichous or peritrichous, parasites on plants. Cultured in the presence of sugars, these organisms produce acid; they are evident allies of the colon group. Erwinia commemorates Erwin F. Smith, the discoverer of many bacteria pathogenic to plants. Typical species cause blights, wilts, or dry necroses. The discovery by Burrill, 1882, of Erwinia amylovora, the cause of the fire blight of pears, should Kingdom Mychota [ 23 have prevented the formulation of a theory, once entertained, that all bacteria require neutral media, and are accordingly incapable of causing diseases of plants. The species of Pectobacterium, as P. carotovorum, cause rots. Those of Agro- bacterium cause galls; A. tumefaciens causes crown gall of many plants. Rhizobium includes the species which produce little galls ("nodules") on the roots of plants and which benefit their hosts by fixing nitrogen. The best known hosts of Rhizobium are plants of the family Leguminosae; the relationship between Leguminosae and Rhizobium is a classic example of symbiosis. There are several or many species of Rhizobium, scarcely distinguishable morphologically, but living on different groups of legumes. The race which was first recognized and isolated, R. Leguminosarum Frank 1890 [Schinzia Leguminosarum Frank 1879; Bacillus Radicic- ola Beijerinck 1888) is that which attacks plants of the pea tribe. Bewley and Hutch- inson (1920) accounted for the variety of forms which Rhizobium can assume. In the roots of plants it occurs as involution forms. In culture, it is a peritrichous rod, but the flagella are often reduced to one, and it has been confused with the mono- trichous bacteria (Conn and Wolfe, 1938). Family 10. Azotobacteriacea [Azotobacteriaceae] Bergey, Breed, and Murray in Bergey's Manual 5th ed., preprint, v and 71 (1938). These are the organisms which were originally isolated by Beijerinck (1901) by inoculating with garden soil shallow layers of a nitrogen-free nutrient solution containing mannite. The commonest species, Azotobacter Chroococcum, is usually seen as ellipsoid cells, as much as \\x thick and 7[J. long, solitary, with peritrichous flagella, or forming non-motile clusters imbedded in a heavy capsule. Beijerinck observed the occurrence of globular involution forms as much as 15^ in diameter. Lohnis and Smith (1916) made a thorough study of variations in form, and reported a remarkable variety of other stages, including the symplasm. The Pasteurellacea and Rhizobiacea are apparently reasonably close allies of the Achromobacteriacea. The Azotobacteriacea stand somewhat apart. The remain- ing families of the present order are more definitely distinct, being marked by mono- trichous or lophotrichous flagella. Family 11. Spirillacea [Spirillaceae] Migula 1894. Family Pseudomonadaceae Winslow et al. in Jour. Bact. 2: 555 (1917). Rods and spirals, Gram negative, mono- trichous or lophotrichous; not producing much acetic acid, and mostly heterotrophic. Pseudomonas is a numerous genus of rods which may or may not produce a fluores- cent pigment soluble in water; they do not produce a yellow pigment which is in- soluble in water. The original species, P. aeruginosa, was isolated from pus, in which it produces a blue-green discoloration; it is by itself weakly if at all pathogenic. Other species have been isolated from fresh and salt waters and brines; the bacteria which produce phosphorescence on salt fish are of this genus. Many further species arc: pathogenic to plants, producing chiefly leaf spots. Phytomonas Bergey et al. 1923 {Xanthomonas Dowson 1948) includes numerous plant pathogens which in culture produce an insoluble yellow pigment; among them are the causes of cabbage rot, walnut blight, and leaf spots on many plants. Pacinia Trevisan 1885 includes monotrichous curved rods. The type species P. cholerae-asiaticae is the cause of Asiatic cholera. Among numerous other species the majority are harmless saprophytes in waters. Recent authorities have treated the cholera organism as the type of the genus Vibrio Miiller (1773); their action is an in- tolerable falsification of the usage of a full century preceding the discovery of the cholera organism. 24 ] The Classification of Lower Organisms Spirillum includes the typical spirals, lophotrichous, a small number of species of harmless saprophytes in foul waters. Thiospira includes large lophotrichous spirals, colorless, containing granules of sulfur. They are believed to live by chemosynthesis. Family 12. Acetobacteriacea [Acetobacteriaceae] Bergey, Breed, and Murray 1938. As gross objects, growths of Acetobacter aceti Beijerinck have been known since prehistoric times. With included yeasts they constitute mother of vinegar (the old names Mycoderma mesentericum Persoon, Ulvina aceti Kiitzing, and Umbina aceti Nageli designated the combination of bacteria and yeasts, and it seems proper to reject them). Free-swimming cells with polar flagella have been observed; ordinarily the cells appear as rods in chains, heavily encapsulated, or as involution forms. The organic food required by Acetobacter is alternatively alcohol, which is oxidized to acetic acid, or acetic acid, which is oxidized to carbon dioxide and water. These processes are strictly aerobic: to make vinegar, one exposes wine to air; to preserve it, one seals the vessels. Family 13. Nitrobacteriacea [Nitrobacteriaceae] Buchanan in Jour. Bact. 2: 349 (1917). Organisms oxidizing the simplest organic compounds; or facultatively capa- ble of chemosynthesis; or living strictly by chemosynthesis and strictly aerobic: mostly Gram negative monotrichous or atrichous rods. Methanomonas is capable of oxidizing methane; Carboxidomonas of oxidizing carbon monoxide; Hydrogenomonas, of oxidizing elemental hydrogen. Thiobacillus includes organisms which oxidize hydrogen sulfide or elemental sulfur. Winogradsky had discovered chemosynthesis in the course of studies of Beggiatoa and other sulfur-oxidizing organisms before he undertook to isolate bacteria which cause nitrification, that is, the natural production of nitrates in soil and waters. He achieved success (1890) by inoculating, with soil or sewage, media which con- tained salts of ammonia but no food; he saw the nitrifying organisms first as minute motile rods which he named Nitromonas. Further study and the use of solid media showed that nitrification takes place in two stages and is the work of several kinds of organisms. Winogradsky distinguished Nitrosomonas europaea and N. javaneyisis, monotrichous rods from different regions as indicated, oxidizing ammonia to nitrites; Nitrosococcus, non-motile spheres from South Amerca, effecting the same oxidation as Nitrosomonas; and Nitrobacter, non-motile rods oxidizing nitrites to nitrates. Subsequent authors have validated Winogradsky's names by creating the combina- tions Nitrosococcus nitrosus and Nitrobacter VVinogradskyi. Subsequently, Winograd- sky discovered yet other bacteria capable of the same oxidations. The presence of nitrifying bacteria is necessary for the normal growth of most crops. So active are the nitrifying bacteria that no more than traces of ammonia and nitrites are found in normal soils, and so avidly do plants absorb nitrates that these accumulate only in fallow fields. Order 2. Actinomycetalea [Actinomycetales] Buchanan in Jour. Bact. 2: 162 (1917). Organisms which consist typically of slender filaments not divided into cells, but which are capable of producing conidia, that is, minute spherical or elongate bodies cut off by constriction from the ends of the filaments, or of breaking up into cells of the form of regular or irregular rods. Non-motile; Gram positive or Gram negative; often of the staining character called acid fast. The order may be treated as a single family. Kingdom Mychota [ 25 Family Mycobacteriacea [Mycobacteriaceae] Chester 1907. Family Actinomyce- taceae Buchanan in Jour. Bact. 3: 403 (1918). Family Streptomycetaceae Waksman and Henrici 1943. Characters of the order. Three genera require discussion. Streptomyces Waksman and Henrici 1943. The original name of this genus is Streptothrix Cohn (1875); there is an older genus Streptothrix among plants, and the numerous species of the present genus have generally been included in Actino- myces. Cultures are readily isolated from air or soil. They appear as slowly growing colonies which may at first be of various colors and have shiny surfaces. Their texture is tough; a blunt needle will more often tear a colony from the medium than pene- trate it. As the colonies grow, they become truncate; the exposed surfaces become white and powdery; pigments, black, brown, red, or yellow, in various races, are produced, and discolor the medium. The toughness of the colonies is a consequence of their structure, of myriad crooked branching filaments about 1|J. in diameter, without joints; the white and powdery surface is produced by myriad conidia released in basipetal succession. The cultures are of an odor which may be described as that of earth under the first rain after drouth: undoubtedly, this familiar odor is that of Streptomyces in the soil. Drechsler (1919), from careful study of several species of Streptomyces, concluded that they are fungi; their filaments are, however, much finer than those of fungi, and no definite nuclei have been seen. Certain species of Streptomyces cause a scabbiness of potatoes. Except for this, the genus was for a long time regarded as quite unimportant. When the capacity of the fungus Penicillium notatum to inhibit the growth of bacteria had been observed, and had led to the discovery of the drug penicillin, Waksman, the leading authority on the classification of Actinomycetalea, sought comparable drugs produced by Streptomyces, and had the great success of discovering streptomycin. Actinomyces Bovis Harz 1877 is one of several species of the same general nature as Streptothrix which are pathogenic to animals. It causes lumpy jaw of cattle. Mycobacterium Lehmann and Neumann 1896 is typified by M. tuberculosis, the agent of one of the most important diseases of man, supposed originally to have attacked cattle, and to have spread around the world with European cattle. It is a chronic disease, destroying the tissues slowly and producing a nugatory sort of im- munity which makes it possible to test for the disease, but does not check it. The cells are recognized in sputum and in diseased tissues by the acid fast reaction: the dye carbol fuchsin must be applied hot in order to color them; once it has done so, it does not wash out in acid alcohol. It is cultivated with difficulty. The growth is dry, powdery, wrinkled, with an odor described as sickening-sweet. It consists of branching filaments which break up readily into rod-shaped or irregular fragments. Lesions of leprosy contain acid fast organisms named Mycobacterium leprae. Gay (1935) has discussed the results of attempts to cultivate this species. They have yielded either "diphtheroid" cells or a "streptothrix." He concludes that most of the reports are of the same organism reacting variously to various conditions. Order 3. Caulobacterialea [Caulobacteriales] Henrici and Johnson in Jour. Bact. 29: 4 (1935). Aquatic bacteria, the cells of most examples secreting gelatinous matter in such a manner as to produce stalks. Henrici and Johnson provided a system of four families, five genera, and nine species. Stanier and van Niel (1941) rejected the group as artificial, placing some of the genera among Eubacteria and leaving others unplaced. The order may be maintained for the accommodation of the latter and divided into two families. 26] The Classification of Lower Organisms m Fig. 3 — a-e, Caulobacterialea after Henrici and Johnson (1935) x 2,000: a, Nevskia sp.; b, Caulobacter vibrioides; c, Caulobacter sp.; d, Pasteuria sp.; e, Blasto- caulis sp. f. Various stages of Cytophaga Hutchinsonii [Spirochaeta cytophaga) after Hutchinson and Clayton ( 1919). g-k, Myxobactralea after Thaxtcr (1892), the cells X 1,000, in the fruits x 200. g, h, Cells and fruit of Chondromyccs crocatus; i, fruit of C. aurantiacus; j,k, vegetative cells and spores, and fruit, of Myxococcus coralloi des. I, m, Dividing cells of Cristispira Veneris after Dobell (1911) x 2,000. Kingdom Mychota [ 27 Family 1. Leptotrichacea [Leptotrichacei] Schroter 1886. The cells not elongated in the direction of the axis of the stalk. Didymohelix ferruginea (Ehrenberg) Griffith (first named, and usually listed, under Gallionella, which is a misspelling of the name of a genus of diatoms) occurs in waters containing iron. Older authors described it as consisting of paired filaments, less than 1^ in diameter, colored bright yellow with imbedded iron oxide, and coiled about each other. In fact, the supposed paired filaments are the margins of a single twisted band, which is not itself an organism but the stalk secreted by a terminal cell. Spirophyllum Ellis is either the same species or a closely related larger one. Leptothrix Kiitzing Phyc. Gen. 198 ( 1843) was inadequately described; the species which was first named, and which is accepted as the type, was L. ochracea. It is be- lieved that this name properly designates the masses of ochraceous matter seen in iron springs. Under the microscope, this matter is seen to consist of fine yellow filaments, straight and unbranched. Ellis (1916) described them as consisting of a cylinder of protoplasm, not divided into cells, enclosed in a sheath. Almost surely, these structures, generally recognized as of the same nature as Didymohelix, are like- wise stalks secreted by minute terminal cells. Siderocapsa Molisch and Sideromonas Cholodny, described as minute spheres or rods imbedded in capsules colored by ferric oxide and attached to plants in waters containing iron, are perhaps to be interpreted as stalkless members of the present group. Nevskia Famintzin, forming minute gelatinous colonies floating on water, does not accumulate iron. Family 2. Caulobacteriacea [Caulobacteriaceae] Henrici and Johnson 1. c. (1935). The cells elongated in the direction of the long axes of the stalks. Caulobacter, Pas- teuria, and Blastocaulis, colorless saprophytes in waters or parasites in aquatic animacules. Class 2. MYXOSCHIZOMYCETES Schaffner Class Myxoschizomycetae Schaffner in Ohio Naturalist 9: 447 (1909). Class Polyyangidae Jahn Beitr. bot. Protistol. 1: 65 (1924). Class Spirochaetae Stanier and van Niel in Jour. Bact. 42 : 459 ( 1941 ) . Parasitic or saprophytic Mychota, the elongate cells with thin walls or none, capable of bending movements and sluggishly or actively motile. In many examples there is a resting stage: the cell contracts generally, so as to diminish the surface, and deposits a definite wall. The structure so produced is a spore of the type called an arthrospore or chlamydospore. The two orders Myxobactralea and Spirochaetalea have not previously been combined to form a separate class. A certain species which Hutchinson and Clayton (1919) described as a spirochaet, Spirochaeta cytophaga, has subsequently been found to be a myxobacterium. The hint of relationship thus conveyed is confirmed by the whole character of both groups, as may be seen from the discussions of them by Stanier and van Niel (1941) and Knasyi (1944). Order 1. Myxobactralea [Myxobactrales] Clements Gen. Fung. 8 (1909). Order Myxobacteriaceae Thaxter in Bot. Gaz. 17: 389 (1892). Order Myxobacteriales Buchanan in Jour. Bact. 2: 163 (1917). The cells not definitely of spiral form, sluggishly motile. In typical examples, the 28 ] The Classification of Lower Organisms cells occur in swarms imbedded in slime; the entire mass moves concertedly, and is eventually converted into macroscopically visible fruiting bodies. The group was first recognized by Thaxter. He took note that the fruiting bodies of Chondromyces had already been described by Berkeley and Curtis as those of a gasteromycete, and learned subsequently that Polyangium Link, also described as of the puffball group, is an older name for his Myxobacter. The swarms of cells live in air on damp substrata (commonly the feces of various kinds of animals), moving across them and digesting and absorbing food as they proceed. Labratory culture is fairly easy. As a reaction, apparently, to exhaustion of the available food, the cells change into chlamydospores; the masses of spores held together by dried slime are called cysts. These may be borne on simple or branched stalks built up from the slime as a preliminary to the formation of the cysts and spores. The group is of essentially no economic importance. The accepted classification is that of Jahn (1924); to the four families which he recognized, one more has been prefixed for the accommodation of the genus Cytophaga. family 1. Cytophagacea [Cytophagacae] Stanier 1940. The chlamydospores formed sporadically by individual cells, not in cysts. Cytophaga Hutchinsonii Wino- gradsky [Spirochaeta cytophaga Hutchinson and Clayton) is one of several species discovered as active fermenters of cellulose. The slenderly spindle-shaped cells are sluggishly motile, and produce ellipsoid chlamydospores resembling yeasts. Family 2. Archangiacea [Archangiacae] Jahn op. cit. 66. Spores elongate in irregu- larly extensive masses, not in cysts. Archangium, Stelangium. Family 3. Sorangiacea [Sorangiaceae] Jahn op. cit. 73. Spores elongate, the cysts angular, in masses, not stalked. Sorangium. Family 4. Myxobacteriacea [Myxobacteriaceae] (Thaxter) E. F. Smith 1905. Family Polyangiaceac Jahn op. cit. 75. Spores elongate, in distinct rounded cysts, clustered or solitary, sessile or borne on simple or branched stalks. Polyangium Link 1795 [Myxobacter Thaxter 1892), Stelangium, Melitangium, Podangium, Chondromyces. Family 5. Myxococcacea [Myxococcaceae] Jahn op. cit. 83. Spores spherical; cysts indefinite or definite. Myxococcus, Chondrococcus, Angiococcus. Order 2. Spirochaetalea [Spirochaetales] Buchanan in Jour. Bact. 2: 163 (1917). Cells solitary, spiral in shape, actively motile. The first known species of this group was Spirochaeta plicatilis, observed in foul waters by Ehrenberg (1838). The next was the species now known as Borrelia recur- rentis (Lebert) Bergey et al., observed in the blood of relapsing fever patients by Obermeier, 1873. During the last years of the nineteenth century, many attempts to identify the agent of syphilis by standard bacteriological methods were unsuccessful. The German government directed Schaudinn and Hoff'mann to continue this work. Fritz Schau- dinn, 1871-1906 (Stokes, 1931), had attained distinction as a student of pathogenic protozoa. Within a few weeks, by the microscopic examination of lesions, he attained success where the bacteriologists had failed, and discovered Treponema pallidum (Schaudinn and Hoffmann, 1905). Spirochaets were first cultivated by Noguchi; few others have been successful in this difficult practice. It requires a medium of aseptic, not sterilized, animal ma- terial, under more or less anaerobic conditions. Each species requires its peculiar variant of the conditions, to which it is quite sensitive. Kingdom Mychota [ 29 Spirochaeta plicatilis and other saprophytic species, together with certain species parasitic in mollusks, are fairly large. The species which are parasitic or commensal in other animals may be extremely small. It is chiefly by study of the larger species that the structure is known. The internal structure is septate. Dobell (1911) found in Cristispira, at the margin of each septum, a whorl of granules staining like chroma- tin, and interpreted these granules collectively as a nucleus. Noguchi (in Jordan and Falk, 1928) saw in the interior of the smaller species no chambered structure, but a lengthwise rod. This has been interpreted as a nucleus, as a locomotor or skeletal structure, or as an artifact. The electron microscope has shown actual flagella at the ends of cells of Treponema pallidum. Reproduction is normally by transverse divi- sion into two. During division, the daughter cells may coil about one another, giving a false appearance of lengthwise division. Gross (1913) observed that Cristispira is capable of breaking up into cylindrical Stdhchen corresponding to the chambers. The discovery of Treponema by an eminent protozoologist; the character of spirochaetal diseases, several of which are spread by biting insects, and produce only that nugatory immunity which makes diagnosis possible but does not check the disease; and the supposed lengthwise division of the cells; led to the hypothesis that the spirochaets are protozoa. Dobell was surely correct in dismissing this hypothesis, insisting that the spirochaets are neither protozoa nor typical bacteria, but a group sui generis. The larger and smaller spirochaets are reasonably treated as separate families. Family 1. Spirochaetacea [Spirochaetaceae] Swellengrebel 1907. The cells com- paratively large, 80-500(1 long. Spirochaeta, Saprospira, Cristispira. Family 2. Treponematacea [Treponemataceae] Robinson in Bergey Man. 6th ed. (1948). Family Treponemidae Schaudinn 1905. The cells 4-15^ long. Treponema Schaudinn. The cells comparatively loosely coiled. T. pallidum, the agent of syphillis. T. pertenue, the agent of yaws. T. macrodentium and T. micro- dentium, harmless commensals in the mouth. Borrelia Swellengrebel is doubtfully distinct from the foregoing; Noguchi reduced it. B. recurrentis and other species cause relapsing fevers. B. Vincenti causes Vincent's angina (trench mouth). The fusiform cells always found associated with it and supposed to be ordinary bacteria of a genus Fusiformis or Fusobacterium may be its chlamydospores. Leptospira Noguchi. The cells tightly coiled. L. icterohaemorrhagiae is the agent of infectious jaundice. L. icteroides, isolated by Noguchi in South America, sup- posedly from cases of yellow fever, is perhaps the same thing: it is now known that yellow fever is caused by a virus. It was in pursuing in Africa his study of yellow fever that Noguchi lost his life by this disease (Flexner, 1929; Eckstein, 1931). Class 3. ARCHSPLASTIDEA Bessey Myxophykea Wallroth 1853. Myxophyceae Stizenberger 1860. Division (of Class Algen) Pkycochromaceae and order Gloiophyceae Rabenhorst Krytog.-Fl. Sachsen 1: 56' (1863). Cyanophyceae Sachs Lehrb. Bot. ed. 4: 248 (1874). OrAtx Cyanophyceae or Pkycochromaceae yicNdLhm]o\iT. oi'Qot. 15: 340 (1877). Schizophyceae Cohn 1879, not suborder Schizophyceae Rabenhorst Deutschland's Kryptog.-Fl. 2, Abt. 2: 16 (1847). 30 ] The Classificatio7i of Lower Organisms Order Schizophyceae Schenck in Strasburger et al. Lehrb. Bot. 1894. Class Schizophyceae Engler in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. la: iii (1900). Class Archiplastideae Bessey in Univ. Nebraska Studies 7: 279 (1907). Class Cyanophyceae Schaffner in Ohio Naturalist 9: 446 (1909). Class Myxophyceae G. M. Smith (1918). Subclass Myxophyceae Setchell and Gardner in Univ. California Publ. Bot. 8, part 1: 3 (1919). Cyanophyta Steinke ( 193 1 ) . Stamm Cyanophyta Pascher in Beih. Bot. Centralbl. 48, Abt. 2: 330 (1931). Mychota most of which live by phytosynthesis of primitive or typical character, many of them, and most of the saprophytic and chemosynthetic organisms included with them, being of the form of sheathed filaments. This is primarily the group of the blue-green algae. Blue-green algae are familiar things as forming dark scums in water and on wet surfaces. Rabenhorst (1863) ap- pears first to have recognized them as a group definitely distinct from green algae; he named most of the recognized families. Revisions by Thuret (1875), Bomet and Flahault (1886-1888), and Gomont (1892) failed to provide a satisfactory system of the group; Kirchner's revision (in Engler and Prantl, 1898) is the accepted system. One of the important contributions of Cohn was his suggestion that the bacteria and blue-green algae belong together. He emphasized this view by mingling the genera of the two groups in two new groups, "tribes," named in effect slime-formers and thread-formers (1875). In this he went too far; but some of the arrangements which he suggested appear natural. Beggiatoa, the type of order Thiobacteria of Migula, appears to be a variant of the common blue-green alga Oscillatoria, differing from it in living by chemosynthesis. Most of the so-called iron bacteria, family Chlamydobacteriaceae of Migula, fall readily into scattered places among the blue- green algae. Only the genus Sphaerotilus remains at loose ends. It is credibly reported to produce cells swimming by means of flagella; no proper blue-green algae do this. A variety of purple bacteria — bacteria, that is, which contain a red pigment — have been discovered from time to time. Engelmarm (1888) observed that they swim toward the light, and convinced himself that they live by photosynthesis. Van Niel confirmed this, and showed that photosynthesis is in this group of a peculiar character; it requires the presence of reducing agents and does not release oxygen. This type of photosynthesis appears, in fact, to represent a stage of the evolution of typical photo- synthesis; the group in which it occurs appears to represent the ancestry of the typical blue-green algae. The poorly known green bacteria appear to belong with the purple bacteria. Various members of this class have been proved capable of fixing nitrogen (Sisler and ZoBell, 1951; Williams and Burris, 1952). Four orders may be distinguished: 1. Possessing a red ("purple") intracellular pigment, or a green pigment not masked by others Order 1 . Rhodobacteria. l.With green pigment masked by others, or colorless. 2. Producing cells with flagella; non-pig- mented sheathed filaments not accumu- lating ferrugineous matter Order 2. Sphaerottlalea. Kingdom Mychota [ 31 2. Never producing cells with flagella. 3. Cells dividing in more planes than one, growing to full size before re- dividing; unicellular or colonial, not filamentous Order 3. Coccogonea. 3. Cells dividing in one plane, and accordingly producing filaments; exceptional examples reproducing by budding (unequal division) or by repeated division into minute spores Order 4. Gloiophycea. Order 1. Rhodobaeteria Molisch Purourbakterien 27 (1907). Rods, spheres, and spirals, solitary or colonial, with red or green pigment, per- forming in the presence of light and reducing substances a sort of photosynthesis in which no oxygen is released. These organisms have generally been included in Thiobacteria, but do not include Beggiatoa, the type of that order. Molisch divided them into two families, Thiorho- daceae, aerobic, accumulating granules of sulfur, and Athiorhodaceae, microaero- philic or anaerobic, not accumulating granules of sulfur. The green bacteria are to be placed as a third family. The names originally applied to the families are not tenable. Family 1. Chromatiacea (Migula) nomen familiare novum. Subfamily Chro- MATiACEAE Migula. Family Rhodobacteriaceae Migula; Family Thiorhodaceae Molisch; the family does not include genera with corresponding names. Purple bac- teria, aerobic, accumulating granules of sulfur. Chromatium Perty includes the or- ganism of foul waters which was originally named Monas Okenii. It is a plump rod, often bent, sometimes exceeding \0\Ji in length, monotrichous or lophotrichous. There are a dozen other genera, rods, spheres, and spirals [Thio spirillum., which belongs here, is to be distinguished alike from Spirillum, Thiospira, and Rho do spirillum), solitary or colonial, motile or non-motile. Most of them were discovered by Wino- gradsky. Family 2. Rhodobacillacea nom. nov. Family Athiorhodaceae Molisch. Molisch named in this family a genus Rhodobacterium, but the name Rhodobacteriaceae had already been applied by Migula to the preceding family. Purple bacteria, anaerobic, not accumulating granules of sulfur. Molisch discovered all known members of the present family. The method of culture was to place a mass of organic matter, for example an egg, in the bottom of a cylinder of water (the original account specified water of the River Moldau), cover the surface with oil, place in a north window, and wait several weeks. This method yielded organisms which were assigned to seven genera. Those of spiral form are Rhodospirillum. All others are by van Niel treated as a single genus, which may be called Rhodobacillus Molisch {Rhodopseudomonas van Niel). Family 3. Chlorobiacea nom. nov. Family Chlorobacteriaceae Geitler and Pascher ex van Niel in Bergey's Manual ed. 6: 869 (1948). Geitler and Pascher (in Pascher Siisswasserfl. Deutschland, 1925) did not place this group in a definite category and name it unequivocally: they called it Cyanochloridinae or Chlorobacteriaceae. Minute spherical or elongate cells with a green pigment different from typical chlorophyll, anaerobic, non-motile, producing irregular or regular gelatinous colonies. Chlorobium, Pelodictyon, Clathro Moris, with a half a dozen known species. Certain 32] The Classification of Lower Organisms Fig. 4. — Coccogonea: a, Chroococcus sp.; b, C, Achromatiuni oxalijerum. Gloio- phycea: d, Oscillatoria splendida; e, Phormidium sp.; f, Beggiatoa sp.; g, Chamae- siphon incrustans; h, Anabaena inacqualis; \, Cylidrospcrmum majus; j, Chlarnydo- thrix ochracea; k, 1, m, Clonothrix fusca after Kolk (1938); n, Dermocarpa protea after Setchell and Gardner ( 1919); o, Crenothrix polyspora after Kolk ( 1938). All X 1,000. Kingdom Mychota [33 organisms of this group, occurring in symbiotic combinations with larger bacteria or with protozoa, have been named as additional genera; one of these is Chlorobacterium Lauterborn, but the name is a later homonym. Order 2. Sphaerotilalea nom. nov. Order Desmobactcrialcs Pribram in Jour. Bact. 18: 376 (1929); there is no cor- responding generic name. Cells colorless, elongate, in sheathed filaments which branch freely in the manner called "false": the cells divide strictly in one plane; those at a distance from the tip may so multiply as to break the continuity of the series by pushing a growing point laterally out of the sheath. The cells may escape from the filaments, become lophotri- chous, and function as swarm spores. There is a single family: Family Sphaerotilacea [Sphaerotilaceae] Pribram 1. c. There is probably only one species, Sphaerotilus natans Kiitzing {Cladothrix dichotoma Cohn). It is found as minute gelatinous colonies fioating on stagnant water; cells 2-4^ in diameter. Order 3. Coccogonea [Coccogoneae] (Thuret) Campbell Univ. Textb. Bot. 84 (1902). Tribe Chroococcaceac [Coccogoneae) Thuret in Ann. Sci. Nat. Bot. ser. 6, 1: 377 (1875). Subclass Coccogoneae Engler in Engler and Prantl Nat. Pfianzenfam. I Teil, Abt. la: iii (1900). Order Coccogonales Atkinson 1903. Orders Chroococcales and Entophysalidales Geitler in Pascher et al. Siisswasserfl. Deutschland 12: 52, 120 (1925). Cells solitary or colonial, not filamentous, never flagellate; mostly of blue-green color and living by photosynthesis. Kirchner (in Engler and Prantl, 1898) placed here two families, Chroococcaceac and Chamaesiphonaceae, but the second belongs to the following order. A proper second family includes the colorless organisms of genus Achromatium. Family 1. Chroococcacea [Chroococcaceac] (Nageli) Rabenhorst Kryptog.-Fl. Sachsen 1:69 (1863). Order Chroococcaceac Nageli Gatt. einzell. Alg. 44 (1849). Unicellular or colonial blue-green algae. Chroococcus, Gloeocapsa, Merismopedia, Coelosphaerium, Gomphosphaeria, etc., occur as plankton or as masses on damp surfaces or the bottoms of bodies of water. Certain species occur as symbionts or parasites within the cells of the green algae Glaucocystis and Gloeochaete. The re- sulting bodies, having the color of blue-green algae with the structure of green algae, resisted classification until Geitler (1923) explained their nature. Family 2. Achromatiacea [Achromatiaceae] Buchanan. Cells solitary, large, ellip- soidal, without flagella, non-pigmented; protoplasm alveolar, with or without granules of sulfur in the alveoli. Half a dozen species have been described; Bersa (1920) was probably correct in reducing all to the original one, Achromatium oxaliferum Schewiakoff. It occurs on mud under still waters rich in organic matter. Order 4. Gloiophycea [Gloiophyceae] Rabenhorst Kryptog.-Fl. Sachsen 1 : 56 (1863). Tribe Nostochineae {Hormonogoneae) Thuret in Ann. Sci. Nat. Bot. ser. 6, 1: 377 (1875). 34 ] The Classification of Lower Organisms Family Hormogoneae Bomet and Flahault in Ann. Sci. Nat. Bot. ser. 7, 3 : 337 (1886). Subclass Hormogoneae Engler in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. la: iii(1900). Order Hormogoneae Campbell Univ. Textb. Bot. 84 (1902). Order Hormogonales Atkinson 1905. Blue-green algae whose cells divide predominantly in one plane, so that filaments are produced, together with related colorless organisms. So far as cell division is strictly in one plane, any branching of the filaments is of the type called "false": it occurs by breaks in the continuity of the series of cells, followed by the outgrowth, beside the original series, of the newly formed tips. In some members of the group, however, the cells are not strictly confined to division in one plane, with the result that "true" branching is possible. There are a few appar- ently derived examples in which cell division takes place freely in all planes. Many of these algae produce spores of the type called arthrospores by the direct conversion of normal cells into thick-walled resting spores. Many (almost but not quite exactly the same ones which produce arthrospores) produce peculiarly differ- entiated cells called heterocysts (the word means "different cells"). These are en- larged thick-walled cells with colorless contents; their most obvious function is to furnish breaking points for the filaments. They are believed to be variants of the arthrospores; they have been seen to germinate and give rise to normal filaments. Ten families may be distinguished as follows: 1. Cells dividing strictly in one plane; branch- ing none or of the "false" type. 2. The filaments not branching nor taper- ing nor producing spores or heterocysts. 3. Filaments elongate. 4. Pigmented, blue-green Family 1. Oscillatoriacea. 4. Colorless organisms accumu- lating sulfur Family 2. Beggiatoacea. 3. Filaments reduced to single cells which reproduce by budding Family 3. Chamaesiphonacea. 2. Filaments branching or tapering, or pro- ducing spores or heterocysts, or showing several of these characters. 3. Filaments not tapering. 4. Filaments not branching Family 4. Nostocacea. 4. Filaments branching. 5. Blue-green algae mostly producing heterocysts Family 5. Scytonematacea. 5. Minute colorless filaments without heterocysts Family 6. Chlamydotrichacea. 3. Filaments tapering Family 7. Rivulariacea. 1. Cells dividing in more planes than one, usual- ly after a preliminary filamentous phase. 2. Pigmented, blue-green. 3. Producing extensive filaments with heterocysts Family 8. Sirosiphonacea. Kingdom Mychota [35 3. Filaments more or less reduced, re- producing by minute spores (gon- idia) formed by repeated division in all planes Family 9. Pleurocapsacea. 2. Colorless; filamentous, reproducing by gonidia Family 10. Crenotrichacea. Family 1. Oscillatoriacea [Oscillatoriaceae] Harvey 1858. Blue-green algae con- sisting of unbranched filaments, not tapering, without spores or heterocysts; mostly actively motile by mechanisms as yet unknown. In the commonest genus, Oscillatoria, the filaments are straight and lack sheaths. Lyngbya and Phormidium produce sheathed filaments, in the latter genus very slender. Microculeus and Hydrocoleum have more than one filament in each sheath. In Arthrospira and Spirulina the fila- ments are coiled; those of Spirulina are not visibly septate, and are said to be uni- cellular. Family 2. Beggiatoacea [Beggiatoaceae] Migula 1895. Beggiatoa Trevisan includes slender colorless filaments, actively writhing, containing granules of sulfur, found in foul waters and sulfur springs. The species were originally included in Oscillatoria. Winogradsky (1887) showed that they live by chemosyn thesis, and discovered the related genera Thiothrix and Thioploca. From the time of these discoveries, these organisms were construed as bacteria of an order Thiobacteria. Under the current hypri thesis that chemosynthesis is a derived character, we are free to believe that the position originally assigned to the species of Beggiatoa was the natural one. Family 3. Chamaesiphonacea [Chamaesiphonaceae] Borzi 1882. Order Chamaesi- pkonales Smith Freshw. Alg. 74 (1933). The only genus is Chamaesiphon, minute organisms epiphytic on freshwater plants. The ellipsoid cells are attached at one end and are enclosed in tenuous sheaths. They reproduce by transverse division, which cuts loose small cells from the free ends. By the time two or three such cells are produced, the sheath is ruptured at the free end, and the small cells drift away to repi educe the organism elsewhere. Family 4. Nostocacea [Nostocaceae] (Nageli) Rabenhorst Kryptog.-Fl. Sachsen 1: 95 (1863). Order Nostocaceae Nageli 1847. Of this family the most familiar genus is Nostoc, seen as gelatinous bodies, usually globular, green, blue-green, yellow, or brown, of sizes from barely visible to the naked eye up to 10 cm. or more in diameter, in fresh water or on damp earth. Under the microscope, these bodies or colonies are seen to consist of myriad crooked and tangled filaments of bead-like cells imbedded in a gelatinous matrix. Heterocysts are always, and spores usually, present. If in water one finds filaments of much the same structure as those of Nostoc, but comparatively short, straight, and free or at least not in definite colonies, these represent the genus Anabaena. Filaments floating on water, with cylindrical spores not confined to the ends of the filaments, are Aphanizomenon. Filaments each with one heterocyst and one spore at one end are Cylindrospermum. Family 5. Scytonematacea [Scytonemataceae] Rabenhorst op. cit. 106. Members of this family produce heavily sheathed filaments like those of Lyngbya, with the difference that heterocysts are usually present. The multiplication of the cells of a filament may produce the result that the cell next to a heterocyst is driven out of line and forced obliquely through the sheath. With further growth, the file of cells ending in one which was forced out of line may appear to be the main axis of a system of branches, while the original summit of the filament appears to be a lateral branch. The description of "false" branching thus given applies particularly to Tolypothrix. 36 ] The Classification of Lower Organisms In Scytonema, the pressure of multiplying cells causes waves of the filament to break laterally through the sheath and produce branches in pairs. Plectonema branches like Tolypothrix but has no heterocysts. Family 6. Chlamydotrichacea [Chlamydotrichaceae] Pribram in Jour. Bact. 18: 377 (1929). Aquatic organisms consisting of colorless cylindrical cells in sheathed filaments, without heterocysts but exhibiting false branching, the sheaths of young filaments thin and colorless, those of older ones thick and yellow to brown. Chlamydo- thrix ochracea Migula was intended as a new name for Leptothrix ochracea Kiitzing, but the entity to which it is believed to apply is totally different from the one to which the latter name was applied above. Chlamydothrix is a filament of definite cells about 1 ^ in diameter. The only other definitely characterized species of this family is Clonothrix fusca Roze, the cells about 2^ in diameter, those near the tips of the fila- ments dividing repeatedly (always in one plane) to produce spherical non-motile gonidia (Kolk, 1.938). Family 7. Fdvulariacea [Rivulariaceae] Rabenhorst op. cit. 101. The filaments include heterocysts and exhibit the false branching of Tolypothrix; the outgrowth of the filament below each heterocyst gives to the original terminal part the appear- ance of a branch of which the heterocyst is the basal cell. The ends of the filaments become attenuate and colorless. In Calothrix the filaments are mostly solitary; in other genera they remain together in gelatinous colonies. Rivularia is without spores; in Glocotrichia there is a large cylindrical spore next to each heterocyst. Family 8. Sirosiphonacea [Sirosiphonaceae] Rabenhorst op. cit. 114. Family Stigonemataceae Kirchner 1898. This family takes its name from the ancient generic name Sirosiphon Kiitzing 1843, which turned out to be identical with Stigonema Agardh 1824. The cells divide at first in one plane and produce filaments. Presently they exhibit a capacity to divide in other planes, and may produce true branches or multiseriate filaments or both. Heterocysts and spc^es are generally produced. Family 9. Pleurocapsacea [Pleurocapsaceae] Geitler in Pascher et al. Siisswasser- Fl. Deutschland 12: 124 (1925). This group was formerly included in Chamaesi- phonacea, but it appears probable that Chamae siphon is related to Oscillatoria, and the present group to Stigonema. Most of the Pleurocapsacea are marine, epiphytic on seaweeds. Their apparently typical behavior, as exemplified by Hyella and Radaisia, consists of the production of branching filaments whose terminal eel's be- come enlarged, after which their contents undergo division in many planes to produce numerous minute spores called gonidia. In Pleurocapsa and Xenococcus there is no filamentous phase; the gonidium gives rise to a cluster of cells all of which produce gonidia. In Dermocarpa the gonidium gives rise to a single vegetative cell which divides only to produce gonidia. Family 10. Crenotrichacea [Crenotrichaceae] Hansgirg. This family includes the single known species Crenothrix polyspora Cohn, one of the traditional iron bacteria. There is every appearance that it is a colorless variant of the Pleurocapsacea. A germi- nating gonidium gives rise to an unbranched filament of cells, about 2^ in diameter, in a sheath which is at first thin and colorless, later becoming thicker and discolored by ferric oxide. Some cells may burst from the free end of the sheath as macrogonidia. Others may begin to divide lengthwise. These may at first grow before re-dividing, and may swell the sheath to a fusiform or trumpet-like shape. By further division they produce numerous microgonidia, which may sift out of the sheath or be re- leased by its decay. Such are the Mychota, the organisms which may properly be characterized as lacking nuclei. Chapter IV KINGDOM PROTOCTISTA Kingdom !l. PROTOCTISTA Hogg Regne Psycho diaire, Psychodies, Bory de Saint Vincent Diet. Class Hist. Nat. 8: 246 (1825), 14: 329 (1828). Kingdom Protozoa Owen Palaeontology 5 (1860), not class Protozoa Goldfuss (1818). Regnum Primigenium seu Protoctista Hogg in Edinburgh New Philos. Jour. n.s. 12: 223 (1860). Kingdom Acrita or Protozoa Owen Palaeontology ed 2: 6 (1861). Kingdom Primalia Wilson and Cassin in Proc. Acad. Nat. Sci. Philadelphia 1863: 117 (1864). Kingdom Protista Haeckel Gen. Morph. 2: xix (1866). Kingdom Protobionta Rothmaler in Biol. Centralbl. 67: 243 (1948). Nucleate organisms other than Plantae and Animalia: the marine algae and the fungi and protozoa. Amiba diffluens may be construed as the standard. The name Protista, of Haeckel, is the most familiar among those which have been applied to the kingdom here to be discussed, but it is not the earliest. Among fol- lowers of Cuvier, the animal kingdom consisted necessarily of four branches. Presum- ably, it was this tradition that induced Owen to refer the Infusoria and Amorphozoa (sponges) to a separate kingdom, which he called Protozoa. A year later, Owen pub- lished an alternative name for this kingdom; but Hogg had already published modi- fications of two of Owen's names, Protoctista and Amorphoctista(KTi^co,to establish, create), for the reason that names in -zoa appeared inappropiiate to groups excluded from the animal kingdom. The limits here given to the kingdom Protoctista were proposed by the present author (1938, 1947). They have been accepted, with exception in a single significant point, by Barkley (1939, 1949) and Rothmaler (1948). It is assumed that the evolutionary origin of the Protoctista consisted of the evolu- tionary origin of the nucleus, and that all nuclei are essentially the same thing. Kofoid (1923) insisted that enduringly viable nuclei originate among protozoa, as among plants and animals, regularly by mitosis, never by binary or multipe fragmentation, nor by aggregation of stainable granules. He did not recognize the nucleus as essen- tially a device for sexual reproduction. Several considerable groups of protozoa, how- ever, which Kofoid listed as not known to reproduce sexually, have been found to do so. Here, then, it is maintained that all nuclei, in this kingdom as among plants and animals, are the same thing; and that the nucleus is essentially a device for sexual reproduction, that is, for processes of reproduction which involve always one act of meiosis and one of karyogamy, and which produce Mendelian heredity as an effect. Photosynthesis is believed to have evolved only cnce. As it occurs both among non- nucleate and nucleate organisms, the nucleus is believed to have evolved in organisms living by this function. The closest approach between non-nucleate and nucleate or- ganisms is believed to be between the blue-green algae and the primitive red algae (Smith, 1933; Tilden, 1933). Thus it appears that the original nucleate organisms were not capable of swimming by means of flagella. Flagella appear to have evolved in unicellular nucleate photosynthetic organisms as a device for dissemination (Bes- 38 ] The Classification of Lower Organisms sey, 1905). The flagella of nucleate organisms are not homologous with those of bacteria; they are much larger and of much more complicated structure. The origin of flagella was apparently associated with a simplification of the system of photosynthetic pigments, by the loss of chromoproteins, leaving systems of chloro- phylls and carotinoids. The association of these two courses of evolution may have been merely coincidental; Tilden suggested the idea that the loss of chromoproteins may have been occasioned by increasing illumination of the waters of the face of the earth. Organisms of the body type of solitary walled cells, having chlorophylls and caro- tinoid pigments but not chromoproteins, and producing flagellate reproductive cells, appear to have undergone radiating evolution, producing a wide variety of types of organisms, distinguished by different specific chlorophylls and carotinoids, different types of flagella, and different specific metabolic products. The types of flagella oc- curring in nucleate organisms are here particularly to be noted. Loeffler (1889), in the original publication of the standard method of staining the flagella of bacteria, remarked that he had applied this method also to certain larger organisms. He found that the flagellum of Manas bears numerous lateral appendages, and that the cilia of a certain infusorian bear solitary terminal appendages. Loeffler's method is difficult, and has not been much used. Fischer (1894) used it and coined terms, Flimmergeisseln and Peitschengeisseln, designating structures of the respective types seen by Loeffler. Petersen (1929), having applied Loeffler's method to a reason- able variety of flagellates, introduced refinements of terminology. Flagella of the type of the larger flagellum of Monas (the organism bears also a minute simple flagel- lum) became allseitswendige Flimynergeisseln; those of Euglena, which bear a single file of appengages, became einseitswendige Flimmergeisseln. Deflandre ( 1934) devised a different method for seeing the appendages on flagella, and substituted, for the Teutonisms just quoted, French terms based on Greek. These may be Anglicised as follows. ( 1 ) The acroneme flagellum bears a single terminal appendage. The flagellum without appendages is said to be simple; so far as it ap- pears among nucleate organisms, it appears to be a variant of the acroneme type. (2) The pantoneme flagellum bears appendages on all sides. (3) The pantacroneme flagellum bears both terminal and lateral appendages. It is a rarity, known only in the collared monads, and may be supposed to be a variant of the pantoneme type. (4) The stichoneme flagellum bears a single file of appendages. The point in which Barkley and Rothmaler take exception to the limits here given to kingdom Protoctista is this, that they include in this kingdom the green algae. In the present work, scant attention is given to organisms whose plastids are bright green, containing chlorophylls a and b, carotin, and xanthophyll, and no other pig- ments; whose motile stages have acroneme flagella, more than one (usually two), and equal; and which produce essentially pure cellulose, true starch, and sucrose. These organisms represent the undoubted evolutionary origin of the higher plants; a classification which attempts to represent nature includes them necessarily in the plant kingdom. Rothmaler set up a system of only four phyla, being the red organisms, basically without flagella; those which are typically yellow to brown, having pantoneme flagel- la; those with acroneme flagella, including the green algae; and the euglcnid group, which have stichoneme flagella. The non-pigmented Protoctista were distributed among these groups. The system appears unsound by the fact that large blocks of non-pigmented organisms are placed where only portions of them belong. Kingdom Protoctista [ 39 In the present work, a less symmetrical system of phyla is offered. Its basis is an ingenuous system of red algae, brown algae, fungi, and the four traditional groups of protozoa; this has been radically modified in view of the great accumulation of knowledge subsequent to the formulation of these groups. The phylum Pyrrhophyta as here limited is tentative; the phylum Protoplasta, marked only by negative char- acters, amounts to a dumping ground for groups whose relationships are altogether obscure. 1. Living by photosynthesis, which takes place in plastids containing red or blue chromo- protein pigments; never producing flagellate cells Phylum 1. Rhodophyta. 1. Without chromoprotein pigments. 2. Typically living by photosynthesis, brown, yellow, or green in color. 3. Producing flagellate cells each with one pantoneme or pantacroneme flagellum, often with additional acroneme flagella Phylum 2. Phaeophyta. 3. Producing flagellate cells whose fla- gella are never pantoneme or pan- tacroneme, often stichoneme Phylum 3. Pyrrhophyta. 2. Dependent; motile cells with acroneme flagella or cilia, or amoeboid, or none. 3. Not producing cilia, i. e., structures of the nature of acroneme flagella, numerous and widely distributed on the surfaces of the cells. 4. Cells walled in the vegetative condition. 5. Producing motile cells with single posterior fla- gella; bodies mostly with tapering rhizoids Phylum 4. Opisthokonta. 5. Producing no motile cells; bodies filamentous Phylum 5. Inophyta. 4. Cells not walled in the vegeta- tive condition. 5. Mostly predatory, flagel- late or amoeboid or with flagellate or amoeboid stages Phylum 6. Protoplasta. 5. Parasitic in animals, pro- ducing flagellate cells only as rare exceptions Phylum 7. Fungilli. 3. With cilia .Phylum 8. Ciuophora. Chapter V PHYLUM RHODOPHYTA Phylum 1. RHODOPHYTA Wettstein Order Floridees Lamouroux in Ann. Mus. Hist. Nat. Paris 20: 115 ( 1813) . Florideae C. Agardh Synops. Alg. Scand. xiii (1817). Order pLORroEAE C. Agardh Syst. Alg. xxxiii (1824). Division (of order Algae) Rhodospermeae Harvey in Mackay Fl. Hibern. 160 (1836). Class Heterocarpeae Kiitzing Phyc. Gen. 369 (1843). Class Florideae J. Agardh Sp. Alg. 1: v (1848). Rhodophyceae Ruprecht in Middendorff Sibirische Reise 1, Part 2: 200 (1851). Stamm Florideae Haeckel Gen. Morph. 2: xxxiv (1866). Phylum RHODOPHYTA Wettstein Handb. syst. Bot. 1: 182 (1901). Division Rhodophyceae Engler Syllab. ed 3: 18 fl903). Phylum Carpophyceae Bessey in Univ. Nebraska Studies 7: 291 (1907). Phylum Rhodophycophyta Papenfuss in Bull. Torrey Bot. Club 73: 218 (1946). Definitely nucleate organisms {Porphyridium and Prasiola doubtfully so); with few exceptions living by photosynthetic processes involving red and blue pigments (phycocyanin and phycoerythrin) as well as green and yellow (chlorophylls a and d and carotinoids); not producing true starch, and producing cellulose only in small quantity, the cells walled chiefly with modified carbohydrates which tend to become gelatinous; never producing flagellum-bearing cells, but sometimes producing cells which move in water without the use of definite organelles. Tilden (1933) and Smith (1933) are authority for placing the red algae next to the blue-green algae, thus suggesting the inference that they include the most primi- tive of nucleate organisms. The resemblances between blue-green and red algae are in the following points. Both groups possess, along with the chlorophylls and carotinoids usual in photosynthetic organisms, other pigments, both blue and red. To these pigments as found in both groups, the same names, phycocyanin and phycoery- thrin, are applied; they are not, however, the same chemical species (Kylin, 1930). Neither group produces true starch; carbohydrate is stored as substances of the general nature of dextrin or glycogen (occuring in the red algae as solid granules called floridcan starch). Both groups produce cellulose only in scant quantities (Miwa, 1940; Kylin, 1943); the cell walls consist chiefly of materials, of the general nature of carbohydrates, which tend to become gelatinous. They share the negative character of never producing flagella, and the positive one of producing cells which call move actively upon surfaces, without motor organelles, by a mechanism as yet unknown (Roscnvinge, 1927). The phylum is divisible into two classes: 1. Cells of most examples each with one central plastid, without protoplasmic interconnec- tions, in aggregates of indefinite extent or or- ganized as filaments or thalli with intercalary growth; zygotes producing spores directly by division Class 1. Bangialea. Phylum Rhodophyta [41 1. Cells with protoplasmic interconnections, containing except in the lowest examples sev- eral parietal plastids, organized as filaments with apical growth, the filaments usually massed as thalloid bodies; zygotes giving rise to spores indirectly Class 2. Heterocarpea. Class 1. BANGIALEA (Engler) Wettstein Subclass Bangioideae de Toni Sylloge Algarum 4: 4 (1897). Subclass Bangiales Engler in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. 2 : ix (1897). Class Bangiales Wettstein Handb. syst. Bot. 1: 187 (1901). Class Bangioideae and orders Bangiales and Rhodochaetales Bessey in Univ. Ne- braska Studies 7: 291 (1907). Class Bangieae SchaflFner in Ohio Naturalist 9: 448 (1909). Protoflorideae Rosenvinge in Mem. Acad. Roy. Sci. Lett. Danemark, ser. 7, Sciences 7: 55 (1909). Abtheilung (of Stamm Rhodophyta) Bangiineae Pascher in Beih. bot. Centralbl. 48, Abt. 2: 328 (1931). Subclass Protoflorideae Smith Freshw. Algae 120 (1933). Red algae (exceptionally green or of other colors), the cells with solitary central plastids (exceptionally with multiple parietal plastids), lacking protoplasmic inter- connections, in irregular colonial masses or forming filaments or thalli with intercalary growth; the zygote produced in sexual reproduction dividing to produce spores directly. The group is of one order, five families, about fifteen genera; the number of known species is about eighty. Order Bangiacea [Bangiaceae] Nageli 1847. Characters of the class. 1. Cells forming irregular aggregates Family 1. Porphyridiacea. 1. Cells forming filaments or thalli. 2. Vegetative cells becoming spores with- out dividing Family 2. Rhodochaetacea. 2. Vegetative cells undergoing division to produce spores. 3. Organisms red, purplish, etc Family 3. Porphyrea. 3. Organisms green Family 4. Schizogoniacea. 2. Spores formed solitary in special cells Family 5. Compsopogonacea. Family 1. Porphyridiacea [Porphyridiaceae] Kylin in Kungl. Fysiog. Sallsk. Forhandl. 7, no. 10: 4 (1937). Order Porphyridiales Kylin 1. c. The only well known species is Porphyridium cruentum (C. Agardh) Nageli (1849). It is widely dis- tributed in damp climates, forming extensive red patches like blood on damp earth or stone. The spherical cells are reported as varying widely in diameter (5-24^), and Geitler (1932) and Kylin (1937) have distinguished additional species. Porphyridium has been classified among blue-green, red, and green algae. Lewis and Zirkle (1920) found in each cell a central red plastid, occupying most of its volume, and having rays extending to the cell membrane. Within the plastid there is 42] The Classification of Lower Organisms Fig. 5. — a, Porphyra laciniata, thallus x 1/2. b-g, Porphyra tenera after Ishikawa (1921); b, cells; c, cell dividing to produce sperms; d, sperms; e, fertilization; f, "carpospores," i.e., cells produced by division of the zygote; g, stages of nuclear division x 2,000. h, i, Porphyra umbilicaris after Dangeard ( 1927); h, fertilization; i, stages of nuclear division x 2,000. All figures x 1,000 except as noted. Phylum Rhodophyta L 43 a moderately large stainable granule; outside the plastid, a single additional granule can usually be found. When a cell is to divide, the granules break up into consid- rable numljers of smaller ones, some of which become organized as a system of strands forming an irregular network on the surface of the plastid. The protoplast, the network, and the plastid undergo constriction; the processes by which the daughter cells return to the original structure were not clearly seen. Interpretation of these observations is difficult. It is possible that the granule outside of the plastid is a nucleus of the type of those which have been observed in Bangia and Porphyra. Family 2. Rhodochaetacea [Rhodochaetaceae] Schmitz in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. 2: 317 (1896). Family Goniotrichaceae Smith Freshw. Algae 121 (1933). Branching filaments, sometimes becoming multiseriate by length- wise division, the vegetative cells capable of escaping and functioning as spores. Sexual reproduction unknown. Asterocystis, uncommon, in fresh water; the remain- ing genera marine, epiphytic on other algae. Goniotrichum. Rhodochaete and Gonio- trichopsis, the cells with numerous plastids. Family 3. Porphyrea [Porphyreae] Kutzing (1843). Family Porphyraceae Raben- horst 1868. Family Bangiaceae (Nageli) Schmitz (in Engler and Prantl, 1896). Filaments or thalli of a red or purple color; the cells, in producing spores, may re- lease their protoplasts as wholes or may undergo division into many. Rosenvinge (1927) observed the active motion of these spores. The most important genus is Porphyra; the individuals are thalli up to several centimeters in diameter, on rocks or other algae in ocean water along coasts. They are called purple lavers, tsu'ai, amanori; they are used as food, for making soup or in condiments, and are extensively cultivated in Japan (Tseng, 1944). Bangia is either freshwater or marine; in structure it differs from Porphyra in having filementous bodies, uniseriate or pluriseriate. During nuclear division in Porphyra tenera as described by Ishikawa (1921), polar appendages form at both ends of the nucleus, which becomes elongate and appears to consist of three strands. The strands break transversely, and each set of three fuses into a mass. Dangeard (1927), dealing with Porphyra umbilicaris and Bangia fusco- purpurea, observed nuclei 5^ in diameter, each consisting of a karyosome, that is, a mass of chromatin, lying in a clear space surrounded by a membrane. In mitosis, the membrane and the unstained matter disappear. Polar appendages grow out from the karyosome, and their tips become cut off as granules which may be regarded as cen- trosomes. The remainder of the karysome becomes organized as two masses, evidently chromosomes, connected to the centrosomes by fibers. Each chromosome divides into two; the daughter chromosomes move to the centrosomes and fuse with them to form karyosomes about which new membranes appear. This description represents a defi- nite, if primitive, process of mitosis. Sexual reproduction, here where we first encounter it, involves differentiated ga- metes. Naked sperms, indistinguishable from spores, move to the surface of other cells which function as eggs. A strand of protoplasm grows through the gelatinous wall of the egg from the sperm to the egg protoplast, and the protoplast of the sperm migrates through the passage thus formed. The zygote divides two or three times, producing spores. During the first two divisions, the two masses of chromatin which appear are somewhat different in appearance from the vegetative chromosomes (Dangeard, op. cit.); it may be supposed that these masses are tetrads and diads, and that the divisions are meiotic. Evidently, this is a life cycle of the primitive type, in which all cells except the zygotes are haploid. 44 ] The Classification of Lower Organisms Family 4. Schizogoniacea [Schizogoniaceae] Chodat. Family Prasiolaceae West. Family Blastosporaceae Wille. Filamemous or thallose algae, freshwater or marine, of the structure of Porphyrea, but of a green color; sexual reproduction unknown. Kylin (1930) found the pigmentation to be that of green algae rather than of red. Copeland (1955) was unable to discern nuclei. The sole genus Prasiola {Schizo- gonium represents a stage of development) is of about fifteen species. Setchell and Gardner (1920) and Ishikawa (1921) suggested the place in Bangiacea here given to this group. Family 5. Compsopogonacea [Compsopogonaceae] Schmitz in Engler and Prantl Nat. Pflenzenfam. I Teil, Abt. 2: 318 (1896). Family Erythrotrichiaceae Smith Freshw. Algae 122 (1933). Filaments, unbranched or branched, uniseriate or pluri- seriate, or thalli. Spore-formation is accomplished by the division of a vegetative cell, by an oblique wall, into two unequal cells; the protoplast of the smaller is released as a spore. Rosenvinge observed the spores of Erythrotrichia cornea to move as far as 140[i per minute. Sexual reproduction is much as in Porphyrea. Erythrotrichia. Erythrocladia. Compsopogon, in fresh water, the cells with numerous parietal plastids. Class 2. HETEROCARPEA Kutzing Class Heterocarpeae Kiitzing Phyc. Gen. 369 (1843). Class Florideae (C. Agardh) J. Agardh Sp. Alg. 1 : v ( 1848). Subclass Florideae Engler in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. 2: ix (1897). Subclass Euflorideae de Toni Sylloge Algarum 4: 4 (1897). Abtheilung (of Stamm Rhodophyta) Floridineae Pascher in Beih. bot. Centralbl. 48, Abt." 2: 328 (1931). As this is the type group of phylum Rhodophyta, most of the synonymy of that name applies to this one also. Red algae whose bodies consist essentially of filaments growing apically, the cells with protoplasmic interconnections, the plastids (except in some of the lowest ex- amples) of the form of multiple parietal disks; the filaments commonly compacted into cylindrical or thallose bodies; zygotes not dividing to form spores directly, pro- ducing spores by budding or indirectly by processes of growth of various degrees of complexity. In undertaking to describe the varied, and often highly complicated, reproductive processes of the typical red algae, one notes that these organisms occur as haploid individuals, and that the majority occur as distinct male and female haploid individ- uals. Sperms (commonly called spermatia) are minute naked protoplasts released from small cells commonly occurring in patches on the surfaces of thalli. The egg is called a carpogonium (Schmitz, 1883). It is the terminal cell of a specialized fila- ment, the carpogonial filament, and bears a filiform terminal extension, the tri- chogyne (Bornet and Thuret, 1867), whose function is to receive the sperms. The cell, often diflferentiatcd, from which the carpogonial filament grows, is the support- ing cell [Trugzelle). In the more primitive members of the class, the zygote gives rise by budding to a mass of cells called the cystocarp. The cells of the cystocarp release their protoplasts as spores called carpospores. These on germination produce haploid individuals like the original ones. The zygote nucleus is the only diploid nucleus in the life cycle; its first divisions arc meiotic. Phylum Rhodophyta [45 In more advanced examples, the first step of development after fertilization con- sists of the establishment of protoplasmic contact between the zygote and other cells. These may be adjacent cells, reached directly, or distant cells, reached by the out- growth of connecting filaments from the zygotes. In the generality of the group, the cells with which contact is made give rise to cystocarps producing carpospores; in this situation, the cells in question are called auxiliary cells. In some examples, the connecting filaments, after making contact with cells called nurse cells, themselves give rise to the cystocarps. The carpospores, in all of these more advanced examples, give rise to diploid individuals. The diploid individuals are of the same vegetative 'ymW''^- :^^>^^ ^■^y i^ •«!» Fig. 6 — Nuclear phenomena in Polysiphonia violacea after Yamanouchi (1906). a, b, c. Stages of mitosis, d, e. Stages of homeotypic division. structure as the haploid individuals, but do not produce spermatia, carpogonia, or cystocarps. Certain cells, commonly scattered and imbedded in the body, produce sets of four spores which are accordingly called tetraspores; these give rise to haploid individuals. This account means that these algae occur typically in somata of four types: male and female haploid individuals; cystocarps, being a preliminary, parasitic, multipli- cative phase of the diploid stage (Janet named this stage the carposporophyte; Drew, 1954); and free-living diploid individuals, reproducing by tetraspores. The produc- tion of carpospores and tetraspores by different individuals of identical vegetative structure explains the oldest name applied to this class, namely Heterocarpea. Understanding of the life cycle of typical Heterocarpea has been reached only by much labor and after a certain amount of confusion. The first significant observations were by Bornet and Thuret (1867). Schmitz (1883) showed that the zygote makes protoplasmic contact with other cells. He supposed that the contact of the zygote with an auxiliary cell is a second sexual fusion {Copulation) following upon proper 46 ] The Classification of Lower Organisms fertilization. Oltmanns (1898) disproved this: he showed that the nuclei of auxiliary cells are inert, and that the nuclei of carpospores are derived entirely from zygote nuclei. Yamanouchi (1906) showed that the chromosome number of carposporic individuals of Polysiphonia violacea is 10, and that that of tetrasporic individuals is 20; and reported much more of the cytology. Centrosomes appear de novo during the earlier stages of mitosis, and fade out and disappear during the later stages. The mitotic spindle is formed, and the chromosomes take their place upon it, within an intact nuclear membrane, which fades out in later stages. In meiosis, which produces the nuclei of tetraspores, the tetrads and diads divide within the original nuclear membrane, which becomes tetrahedrally lobcd, and then disappears except where the haploid groups of chromosomes lie against it, with the result that the membranes of the tetraspore nuclei are partly old and partly new. There are some 2500 species of Heterocarpea, including comparatively few in fresh water, but the majority of the marine algae. Many of them are beautiful; their variety and beauty contribute to the pleasure which people find on coasts. Exper- ienced naturalists can identify many genera by gross structure, but the systems of orders and families based on gross structure, such as those of Kiitzing (1843) and J. Agardh (1851-1863), have been found artificial and abandoned. A proper respect for the principles of nomenclature makes it necessary, however, to apply many of the names used in these systems. Schmitz applied his morphological studies to a classifica- tion of the typical red algae as four groups ( 1889) ; Engler ( 1897) made these groups definitely orders. Subsequent scholars have found this system sound in principle, but have found it necessary, on the basis of studies of additional examples (for example, by Kylin, 1923, 1924, 1925, 1928, 1930, 1932; Papenfuss, 1944; Sjostedt, 1926; Svedelius, 1942) radically to rearrange the families and genera. At least four orders in addition to those of Engler have been proposed but reductions have decreased the number currently recognized to six. The following key to the orders is a rather considerable modification of those pub- lished by Kylin (1932) and Smith (1944). l.All free-living individuals haploid; tetra- spores not produced, or produced as carpospores. . Order 1. Cryptospermea. 1. Free-living individuals of two types, the one producing gametes (the zygotes giving rise to carpospores), the other producing tetraspores. 2. Without specialized auxiliary cells or nurse cells, the lower cells of the carpo- gonial filaments, or normal vegetative cells, serving as auxiliary cells Order 2. Sphaerococcoidea. 2. With specialized nurse cells, the carpo- spores produced from filaments which have made contact with these Order 3. Gelidialea. 2. With specialized auxiliary cells from which the carpogonia develop. 3. The auxiliary cells being intercalary cells in specialized filaments homol- ogous with the carpogonial filaments. . . . Order 4. Furcellariea. 3. The auxiliary cells terminal in fila- ments which grow from the support- ing cells of the carpogonial fila- ments before fertilization Order 5. Coeloblastea. Phylum Rhodophyta [ 47 3. The auxiliary cells originating after fertilization as branches of the sup- porting cells of the carpogonial filaments Order 6. FLORroEA. Order 1. Cryptospermea [Cryptospermeae] Kiitzing Phyc. Gen. 321 (1843). Order Periblasteae Kutzing op. cit. 387, in part. Orders H elmint hoc lade ae J. Agardh Sp. Alg. 2: 410 (1851), Chaetangieae op. cit. 456 (1851), and Wrangelieae op. cit. 701 (1863). Order Batrachospermaceae'R.ahtnhovstKxy^X.og.-Yl.^dichstn 1: 278 (1863). Nemalioninae Schmitz in Flora 72: 438 (1889). Order Nemalionales Engler in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. 2: ix (1897). Heterocarpea normally without diploid bodies, the carpogonium arising from the zygote or from an adjacent cell serving as an auxiliary cell, the carpospores produc- ing haploid bodies like the original ones. Certain genera which are exceptional to these characters are noted below. Batrachospermum may be regarded as the standard genus. In all recent literature, this order is called Nemalionales. Eight families are rec- ognized. The forms consisting of mere filaments, Acrochaetium, Rhodochorton, and others, are family Acrochaetiacea [Acrochaetiaceae] Fritsch (Family Chantransi- aceae Auctt., but Chantransia DC. as originally published included no members of this family; Papenfuss, 1945). In the remainder of the order, the filaments are differentiated, or, with or without differentiation, organized as bodies of definite form, simply cylindrical, branched, or flattened. Fresh-water examples (the only fresh-water Heterocarpea) include Batrachospermum, Lemanea, and Thorea. These organisms are not red, but bluish, green, or brown. Marine examples include Nemalion and Cumagloia. In Liagora tetrasporifera and certain other species tetraspores are produced in the place of carpospores. Within this genus, then, there has been a change in the time of meiosis (which could be established, presumably, by a single mutation) from im- mediately after fertilization to the end of the cystocarp stage. Galaxaura is a genus of tropical marine algae which are calcified, which is to say that they deposit much calcium carbonate in the tissues; they were originally classi- fied as corals. They have distinct sexual and tetrasporic stages. Svedelius (1942) as- certained their life cycle. Carpospore-bearing filaments arise both from the zygote and from other cells, previously undifferentiated, which serve as auxiliary cells. The genus has the structure of the present order, and is to be placed here, in spite of ex- hibiting in unspecialized form the life cycle of the following orders. Order 2. Sphaerococcoidea [Sphaeroccoideae] J. Agardh Sp. Alg. 2: 577 (1852). Family Gigartineae Kiitzing (1843). Orders Gigartineae and Chaetangieae J. Agardh op. cit. 229, 456 (1851). Gigartininae Schmitz in Flora 72: 440 (1889). Order Gigartinales Engler in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. 2: X (1897). Order Nemastomatales Kylin in Kgl. Fysiog. Sallsk. Handl. n. f. 36, no. 9 : 39 (1925). Order Sphaerococcales Sjostedt in Kgl. Fysiog. Sallsk. Handl. n. f. 37, no. 4: 75 (1926). 48] The Classification of Lower Organisms (Legend on bottom of page 49) Phylum Rhodophyta [ 49 This order, in all recent literature called Gigartinales, is a numerous and varied one. The bodies are generally erect; they may be cylindrical or flattened, unbranched or branched. In some examples, Haliarachnion, Rhodophyllis, Sebdenia, the zygote sends out extensive filaments, which make contact with unspecialized cells scattered in the body. In other examples, the zygote makes contact with a lower cell of the carpogonial filament. In either case, the cells with which contact is made are auxiliary cells and give rise to cystocarps; these produce carpospores, and the carpospores pro- duce tetrasporic individuals. Certain species of Phyllophora, Gymnogongrus, and Ahnfeldtia are exceptional in producing tetraspores in the place of carpospores; these species have no free-Uving tetrasporic generation. In these organisms, as contrasted with Liagora tetrasporifera, it is believed that this type of Ufe cycle has been estab- lished by reduction of a longer one. Kylin (1932) assigned twenty families to this order. Gracilaria is a minor source of agar agar. Gigartina mammilosa and Chondrus crispus (Irish moss or carageen) are well known as yielding a jelly, carageenin, resembling but distinct from agar agar (Tseng, 1945). Various abnormal growths on red algae have been found to be parasitic red algae, almost always on hosts closely related to themselves (Setchell, 1914). To the present order belong Gardneriella and its host Agardhiella; Plocamiocolax and its host Plo- camium; Gracilariophila and its host Gracilaria (Wilson, 1910). Order 3. Gelidialea [Gelidiales] Kylin in Kgl. Svensk. Vetensk.-Akad. Handl. 63, no. 11: 132 (1923). Family Gelidieae Kiitzing (1843). Order Gelidieae J. Agardh Sp. Alg. 2: 464 (1851). Heterocarpea in which the zygote sends out a single elongate filament which makes contact successively with several chains of nurse cells and gives rise to carpospores; bodies consisting of branched filaments, the ultimate tips of the lateral branches compacted into a firm layer covering a branching body, cylindrical or flattened; the surface adjacent to the masses of carpospores pushed out and punctured by pores through which the spores escape. There is a single family Gelidiea [Gelidieae] Kiitzing ( Family Gelidiaceae Schmitz and Hauptfleisch). Such economic importance as the red algae possess lies chiefly in Fig. 7 — a, Thallus of Nemalion multifidum x 1. b, c, d^ production of sperms; beginning of production of carpospores; and cluster of carpospores of Nemalion multifidum after Bornet and Thuret (1867). e, Thallus of Chondrus crispus x 1. {, Reproduction of Dudresnaya purpurifera (order Furcellariea or Cryptonemiales) after Bornet and Thuret, op. cit. The trichogyne, whose free end with attached sperms is seen above, is irregularly twisted below; it leads to the egg (carpogonium); connecting filaments, growing from cells below the egg, make contact with auxiliary cells at the summits of specialized filaments; each auxiliary cell gives rise to a cluster of carpospores. g, Thallus of Delesseria sinuosa x 1. h^ Longitudinal section of conceptacle of Polysiphonia nigrescens x 500, after KyUn (1923). The zygote z is the fourth and terminal cell of the carpogonial filament whose connection with the supporting cell b is not shown; the auxiliary cell a has grown from the supporting cell after fertilization. 50 ] The Classification of Lower Organisms this family, and particularly in the genus Gelidium. It is the chief source of agar agar. This is the principal material of the cell walls of Gelidium. It is a jelly consisting essentially of chains of galactose units, and has the property, that having been melted by heat, it does not again become solid until cooled to a much lower temperature. Algae containing it have long been used as foods in the orient. Brought into labora- tory use by Koch, it has become a necessity in routine bacteriological work. The chief source is Japan. Kylin construed this order as relatively primitive; but its reproductive processes, involving specialized nurse cells, appear less primitive than those of the Sphaerococ- coidea. The production of elongate connecting filaments is shared with certain examples both of the preceding order and of the following, and the Gelidialea are probably derived by specialization from one or the other. Order 4. Furcellariea [Furcellarieae] Greville Alg. Brit. 66 (1830). Orders Spongocarpeae and Gastrocarpcae Greville op. cit. 68, 157 (1830). Order Epiblasteae Kiitzing Phyc. Gen. 382 (1843). Orders Cryptonemeae, Dumontieae, Squamarieae, and Corallineae J. Agardh Sp. Alg. 2: 'l55, 346, 385 (1851), 506 (1852). Cryptoneminae Schmitz in Flora 72: 452 (1889). Order Cryptonemiales Engler in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. 2: xi (1897). The individuals are crustose or thallose, the thalli cylindrical or flattened, un- branched or branched. On the two or three types of individuals of each species, the reproductive structures may be scattered or clustered on the surfaces or gathered in specialized pits called conceptacles. The eggs are as usual the terminal cells of spe- cialized filaments; other filaments, homologous with these but abortive, bear the auxiliary cells. After fertilization, the zygote may or may not establish connection with a lower cell of the same filaments. Under either circumstance, it sends out fila- ments which establish connection with the auxiliary cells, and these send out filaments which bear the carpospores. In less specialized examples, the filaments growing from the zygote may extend widely through the body; a single one, branching, may reach many auxiliary cells. Kylin ( 1932) placed nine families here. The family Corallinea [Corallineae] Kiitzing (family Corallinaceae Hauck) is one of the more specialized. The eggs, and subsequently the carpospores, are clustered in conceptacles. In each conceptacle the zygotes, the filaments from them, and the auxiliary cells, unite eventually in a single large multinucleate cell from whose mar- gins grow the filaments which bear the carpospores. Members of this family have the property of accumulating and depositing calcareous material, and were originally classified as corals. In modern usage, the term coral means certain lower animals; but the coralline algae are associated with them in coral reefs, being indeed, accord- ing to Setchell (1926) and other authorities, responsible for the building of the reefs. Fossil coralline algae are known from the Ordovician. The parasite Callocolax and its host CallophylUs belong to this order; Coreocolax, belonging to this order, attacks species of order Floridea. The Furcellariea are a numerous group, rather unspecialized, varied almost to the extent of a miscellany. They are related to the Sphaerococcoidea, and are believed to represent the ancestry of the two following orders, and possibly also of the Gelidialea. Phylum Rho do phyta [51 Order 5. Coeloblastea [Coeloblasteae] Kutzing Phyc. Gen. 438 (1843). Order Rhodymenieae J. Agardh Sp. Alg. 2: 337 (1851). Rhodymeninae Schmitz in Flora 72: 442 (1889). Order Rhodymeniales Engler in Engler and Prantl. Nat. Pfllanzenfam. I Teil, Abt. 2: X (1897). Heterocarpea producing auxiliary cells terminally on brief filaments which grow from the supporting cells of the carpogonial filaments before fertilization; cystocarps enclosed in cup- or vase-like pericarps; the thalli (cylindrical or flattened, branched or unbranched) usually hollow. Champia may be regarded as the standard genus. In various red algae, the germinating carpospore or tetraspore gives rise to a globe of cells which grows to produce the thallus (Kylin, 1917). In the present group the sporeling is particularly blastula-like. Its upper layer of cells becomes a ring of apical cells, of definite number, distinguishing the group from others which grow by apical cells either of a single filament or of a fascicle of indefinite number. The apical cells are indeed homologous with the apical cells of filaments, but the cells derived from them are arranged in a three-dimensional pattern as in the tissues of higher organisms; it is only in the reproductive structures that the filamentous structure remains evident. The order thus limited by Kylin (1932) is a specialized group including only the two families Rhodymeniacea [Rhodymeniaceae] Hauck and Champiea [Champieae] Kiitzing. The latter family is the more specialized; the hollow thalli are partitioned by transverse septa and the supporting cells produce usually just two auxiliary cells. In many examples of this family, after fertilization and the fusion of the zygote with the auxiliary cells, the latter proceed to unite with further neighboring cells to pro- duce a massive coenocyte from which the brief carpospore-bearing filaments arise. The resulting structure is deceptively similar to that which occurs in the Corallinea. The parasite Faucheocolax and its host Fauchea belong to this order. Order 6. Floridea [Florideae] C. Agardh Syst. Alg. xxxiii (1824). Order Floridees Lamouroux in Ann. Mus. Hist. Nat. Paris 20: 115 (1813). Section Florideae C. Agardh Synops. Alg. Scand. xiii (1817). Orders Trichoblasteae, Axonoblasteae, and Platynoblasteae Kiitzing Phyc. Gen. 370,413,442 (1843). Orders Ceramieae, Spyridicae, Chondrieae, and Rhodomeleae J. Agardh Sp. Alg. vol. 2 (1851-1863). Ceramiales Oltmanns Morph. u. Biol. Alg. 1: 683 (1904). Order Ceramiales Kylin in Kgl. Svensk. Vetensk.-Akad. Handl. 63, no. 11 : 132 (1923). The Floridees of Lamouroux included the whole group of red algae organized as four genera, Chondriis Stackhouse and the new genera Claudea, Delesseria, and Gelidium. Lamouroux listed first Claudea and Delesseria, belonging to the present order, to which the name is accordingly applied. This order is characterized by specialized strict patterns in the development of the feniale reproductive structures. The carpogonial filament is always of four cells. The supporting cell initiates, in definite patterns, brief additional filaments. After fertili- zation, the supporting cell cuts off one more cell adjacent to the zygote, and this be- comes the auxiliary cell. The spore-bearing structures developed from it are naked in the more primitive examples; in most, they are protected by pericarps, which, in some examples, begin to develop before fertilization. There are four families, all numerous in species: Ceramiea (Harvey) Kutzing, 52 ] The Classification of Lower Organisms Dasyea Kiitzirxg, Delesseriea Kutzing, and Polysiphoniea Kiitzing [Rhodomelaceae Hauck). The Ceramiea are mostly filaments, uniseriate or becoming pluriseriate by lengthwise divisions. In many members of the other families the bodies are thallose, though consisting essentially of filaments produced in definite patterns. In many Delesseriea the branches of the thalli simulate leaves of higher plants. Gonimophyllum is parasitic on Botryoglossum; both are Delesseriea. Various species of Janczewskia, a genus of Polysiphoniea, attack Laurencia, Chondria, and other members of the same family. This was the first genus of parasitic red algae to be recognized as such, by Solms-Laubach (1877). Such are the red algae. The Bangialea appear to represent the transition between the organisms which lack nuclei and the generality of nucleate organisms. The Heterocarpea appear to be a specialized offshoot, leading to no other group. Chapter VI PHYLUM PHAEOPHYTA Phylum 2. PHAEOPHYTA Wettstein FucoroEAE C. Agardh Synops Alg. Scand. ix (1817). Orders Diatomeae and Fucoideae C. Agardh Syst. Alg. xii, xxxv (1824). Stamme Diatomea and Fucoideae Haeckel Gen. Morph. 2: xxv, xxxv (1866). Stamme Zygophyta in part and Phaeophyta Wettstein Handb. syst. Bot. 1: 71, 171 (1901). Divisions Zygophyceae in part and Phaeophyceae Engler Syllab. ed. 3: 8, 15 (1903). Chysophyta, with subordinate groups Chrysophyceae, Bacillariales, and Hetero- kontae, Pascher in Ber. deutschen bot. Gess. 32: 158 (1914). Stamm Chrysophyta Pascher in Siisswasserfl. Deutschland 11: 17 (1925). Phyla Chrysophycophyta and Phaeophycophyta Papenfuss in Bull. Torrey Bot. Club 73: 218 (1946). Organisms typically living by photosynthesis, without chromoprotein pigments, the plastids containing chlorophylls a and c, carotin, and various xanthophylls. Lutein (the xanthophyll of typical plants) may be present but is usually exceeded in quantity by flavoxanthin, violoxanthin, isofucoxanthin, or fucoxanthin, particularly the last. The xanthophylls occur usually in quantity sufficient to give the organisms a yellow or brown color. True starch is not produced. Many examples contain granules of a white solid called leucosin, presumably a carbohydrate, which does not give a blue color with iodine. The cells are usually enclosed in walls consisting of cellulose to- gether with larger quantities of other carbohydrates or oxidized or esterized carbo- hydrates. Silica or calcium carbonate may be deposited. Methanol extracts of the cells contain fucosterol, a sterol distinct from the sitosterol of typical plants. Flagel- late cells are usually produced; these bear one pantoneme or pantacroneme flagellum, and usually, in addition, one acroneme or simple flagellum. Exceptional examples, non-pigmented or without flagellate stages, are rather numerous. The obvious stand- ard genus of the phylum is Fucus L. The chemical characters are stated on the authority chiefly of Carter, Heilbron, and Lythgoe (1939), Miwa (1940), and Tseng (1945). The character of the flagel- lation, positively known of rather few examples, is stated by authority of Petersen (1929), Vlk (1931, 1939), Couch (1938, 1941), Longest [1946), Manton (1952), and Ferris (1954). These characters bind together an assemblage of organisms which is in some re- spects original herel. Engler (1897), West (1904), and Smith (1918, 1920) included the chrysomonad flagellates in the group of brown algae. Pascher (1914) combined as or!e group the chrysomonads, the diatoms, and the exceptional green algae called Heierokontae. Later (1927, 1930), he included also the colorless flagellates of family Moiiadina. He did not associate this group with the brown algae, and subsequent authors have in general followed him. Kylin ( 1933 ) , however, considered the diatoms to be the closest allies of the brown algae, both groups being descended from the brown flagellates. Almost certainly, he was correct. Couch showed that the paired unlike flagella of the typical Oomycetes are respectively pantoneme and acroneme, iManton (1952) recognized this group, but omitted nomenclatural formalities. 54] The Classification of Lower Organisms Fig. 8. — Ochromonadalea: a, b, Chrysocapsa paludosa after West (1904); a, a colony; b, zoospores. C-f, Phaeocystis globosa after ScherlTel (1900); c, a colony X 50; d, a cell with two plastids, a mass of leucosin forming on a mound of proto- plasm projecting into the central vacuole; e, production of zoospores; f, a zoospore. g, h. Cell and statospore of Ochromonas granularis after Doflein (1922). i, Cell of Monas sp. j. Two cells of Brehmiella Chrysohydra after Pascher ( 1928) . k, A very young colony of Dendromonas virgaria after Stein (1878). 1, Colony of Ccphalo- thamnium Cyclopum after Stein, op. cit. m. Cells of Epipyxis utriculus after Stein, op. cit. n. Colony of Synura Uvella. x 1,000 except as noted. Phylum Phaeophyta [ 55 and distinguished these fungi from practically all others by the presence of cellulose in their walls. The phylum thus assembled may be organized as four classes. 1. Miscellaneous groups, mostly small and rela- atively unspecialized, of varied body type; not of the characters of the following groups Class 1. Heterokonta. 1. Comparatively numerous and specialized groups. 2. Unicellular brown organisms with shells of silica consisting of two parts Class 2. Bacillariacea. 2. Organisms of fungal or chytrid body types producing swimming spores with paired unlike fiagella Class 3. Oomycetes. 2. Filamentous and thallose brown algae Class 4. Melanophycea. Class 1 . HETEROKONTA Luther Class Flagellata or Mastigophora Auctt., in part. Class Heterokontae Luther in Bihang Svensk. Vetensk.-Akad. Handl. 24, part 3, no. 13: 19 (1899). Subclass Chrysomonadineae Engler in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. la: iv (1900). Class Silicoflagellatae (Borgert) Lemmermann in Ber. deutschen bot. Gess. 19: 254 (1901). Phylum Siphonophyceae and class Vaucherioideae Bessey in Univ. Nebraska Studies?: 285, 286 (1907). Chrysophyceae and Heterokontae Pascher in Ber. deutschen bot. Gess. 32: 158 (1914). Divisions Chrysophyceae and Heterokontae, and classes Chrysomonadineae , Rhizo- chrysidineae, Chrysocapsineae, Chrysosphaerineae, Chrysotrichineae, Hetero- chloridineae, Rhizochloridineae, Heterocapsineae, Heterococcineae, Hetero- trichineae, and Heterosiphoneae Pascher in Beih. bot. Centralbl. 42, Abt. 2: 323,324 (1931). Classes Ebriaceae, Silico flagellata, and Coccolithophoridae Deflandre, and Chrys- omonarfina Hollande in Grasse Traite Zool. 1, fasc. 1: 407,425,438, 471 (1952). Class Phytomastigophorea Hall Protozoology 117 (1953), in part. Phaeophyta which lack the distinctive characters of the remaining three classes. Luther named the group on the occasion of his discovery of Chlorosaccus, and this genus may be regarded as the type. The chrysomonad flagellates are the core of this class and of the first two among the five orders into which it is divided. In the classification of these two orders, three novelties will be noted. (a) Pascher (1913) made of the chrysomonad flagellates three orders character- ized respectively by paired unequal flageila, paired equal flagella, and solitary fiagella. Petersen (1929) found that the supposedly equal fiagella of Synura are actually unlike, being respectively pantoneme and acroneme. Here, accordingly, Pascher's first two orders are combined. (b) Pascher made separate classes or orders of groups related to the chrysomonad flagellates but of distinct body type, as palmelloid, chlorococcoid, filamentous, or 56] The Classification of Lower Organisms Fig. 9. — Ochromonadalea : a, Mallomonas roseola, based on Stein (1878) and Conrad (1926). h, Syracosphaera Quadricornu; c, Calyptosphaera insignis; d, Cal- ciconus vitreus; after Schiller (1925). Silicoflagei.lata: e, f, Colony and zoospore of Epichrysis after Pascher (1925). g, Part of the thallose growth of Hydrurus foetidus. h, Cell, and i, j, statosporos of Chromulina Pascheri after Hofeneder (1913). k, 1, Skeletons of Dictyocha Fibula and Distephanus Speculum from di- atomaceous earth at Lompoc, California, m, Rhizochrysis Scherffeli after Doflein (1916). Mix 1,000. Phylum Phaeophyta [57 amoeboid. By Pascher's own principle of the repeated evolution of body types, these groups are surely artificial. Here most of them are broken up and their mem- bers distributed between the two chrysomonad orders according to whether the flagella of their motile stages are paired or single. It is not possible to divide by this character ameboid forms not known to produce flagellate stages; these are lumped in the second order. fc) Since flagella appear to have evolved as a device for the dissemination of unicellular pigmented organisms, examples whose vegetative state is that of clusters of non-motile cells are placed in each order before those which are flagellate in the vegetative condition. The two chrysomonad orders are particularly characterized by production of leucosin. They are further characterized by production of resting cells of a type called statospores. This occurs by the deposition within the protoplast of a globular shell impregnated with silica, punctured by a single pore, and often marked on the outer surface by warts, spines, or ridges, of definite pattern. The external protoplasm migrates through the pore to the interior of the shell, and the pore is then closed by deposition of a silicified plug. The group which is treated as the third order of the present class includes the typical Heterokonta. Compared with typical green algae, these organisms give the impression of a markedly distinct class; placed next to the chrysomonads, they appear scarcely entitled to this rank. Their name is the oldest applicable to the present class, and is accordingly so applied. If it appear expedient to maintain the typical Heterokonta as a distinct class, the remainder of the present one will be called Chrysomonadinea [Chrysomonadineae] (Engler) Pascher. Of including the choanoflagellates and anisochytrids in the present class as addi- tional orders, one may say that it is not contrary to current knowledge. 1. Mostly pigmented; non-pigmented examples mostly producing motile cells with two fiagella. 2. Brown or colorless. 3. Producing motile cells with two flagella (exceptionally more) Order 1. Ochromonadalea. 3. Producing motile cells with one flagellum; or without known flagel- late stages Order 2. Silicoflagellata. 2. Green Order 3. Vaucheriacea. 1. Non-pigmented, producing motile cells with one flagellum. 2. Predatory, flagellate in the vegetative condition, each cell bearing a collar-like protoplasmic ridge Order 4. Choanoflagellata. 2. Parasitic or saprophytic, the vegetative cells non-motile, walled Order 5. Hyphochytrialea. Order 1. Ochromonadalea [Ochromonadales] Pascher Siisswasserfl. Deutschland 2: 10,51 (1913). Suborder Monadina Biitschli in Bronn KI. u. Ord. Thierreichs 1 : 810 (1884). Order Isochrysidales Pascher op. cit. 10, 42. Order Syracosphaerinae Schiller in Arch. Prot. 51: 108 (1925). 58] The Classification of Lower Organisms Orders Heliolithae and Orthlithinae Deflandre in Grasse Traite Zool. 1, fasc. 1: 452, 457 (1952). Brown or colorless Heterokonta, the swimming cells of typical examples with two flagella which are respectively pantoneme and acroneme. In the exceptional family Trimastigida there are a pair of equal flagella and a third flagellum shorter or longer than these; the detailed structure of the flagella of this family is unknown. Cells of pigmented types contain usually one or two lateral band-shaped plastids. Details of nuclear division are known chiefly by the observations of Doflein (1918, 1922) on Ochromonas. The flagella spring from a granule which may be identified as a blepharoplast, near which lies the nucleus. The blepharoplast is connected through two stainable strands (rhizoplasts) to two granules, recognizable as centrosomes, on the two sides of the nucleus. The spindle forms within the intact nuclear membrane with its poles at the centrosomes. The chromosome number appears to be about 4. The nuclear membrane presently disappears. At metaphase, the rhizoplasts are found to lead to separate blepharoplasts, each bearing two flagella. Sexual processes are scarcely known in this group. Schiller (1926) observed in Dinobryon the division of calls into two which are released to swim and conjugate in pairs. This order is believed to represent the direct ancestry of the two following, and also of the typical brown algae. 1. Not filamentous. 2. Flagellate stages with a pair of equal flagella and a third which is shorter or longer Family 1. Trimastigida. 2. Flagellate stages with two unequal flagella. 3. Without calcareous structures at- tached to the cell walls. 4. Cells not enclosed in loricae, i. e., open shells. 5. Not flagellate in the vege- tative condition Family 2. Chrysocapsacea. 5. Flagellate in the vegeta- tive condition, not forming free-swimming circular or globular colonies Family 3. Monadina. 5. Free-swimming circular or globular colonies Family 4. Syncryptida. 4. Cells enclosed in loricae Family 5. Dinobryina. 3. With calcareous structures at- tached to the cell walls Family 6. Hymenomonadacea. 1. Filamentous Family 7. Phaeothamnionacea. Family 1. Trimastigida [Trimastigidae] Kent Man. Inf. 1: 307 (1880). Family Trimastigaceae Senn in Engler and Prantl. Nat. Pflanzcnfam. I Teil, .\bt. la: 141 (1900). Family Prymncsiidae Hall Protozoology 127 (1953). Organisms producing swimming cells with a pair of equal flagella and a third flagellum longer or shorter than these. With a vegetative stage as globular non-motile colonies as large as pin- heads, of pigmented cells; marine: Phacocystis. Motile solitary cells, pigmented: Prymncsium, Chrysochromidina; Platychrysis with an amoeboid stage. Motile solitary cells, not pigmented: Dallingeria, Trimastix, Macromastix. Phylum Phaeophyta [ 59 Family 2. Chrysocapsacea [Chrysocapsaceae] Pascher in Siisswasserfl. Deutschland 2: 85 (1913). Family Chrysocapsidae Poche in Arch. Prot. 30: 156 (1913). Non- motile cells with brown plastids (usually two), imbedded in gelatinous matter and forming colonial aggregates, the protoplasts sometimes escaping as zoospores with two flagella. Chrysocapsa Pascher, in fresh water, the colonies few-celled. Phaeo- sphaera West and West, the colonies more extensive. Family 3. Monadina Ehrenberg Infusionsthierrhen 1 (1838). Family Monades Goldfuss ( 1818), the mere plural of a generic name. Family Dendromonadina Stein Org. Inf. 3, I Halfte: x (1878). Family Monadidae Kent (1880). Family Hetero- monadina Biitschli in Bronn Kl. u. Ord. Thierreichs 1: 815 (1884). Family Chryso- monadaceae Engler in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. 2: 570 (1897), not family Chrysomonadina Stein. Family Ochromonadaceae Senn in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. la: 163 (1900). Family Ochro- monadidae Doflein. Pigmented or colorless Ochromonadalea, flagellate in the vegetative condition, not forming circular or globular free-swimming colonies, nor loricate, nor bearing calcareous structures on the cell walls (these being the distinc- tions respectively of the three following families). Ochromonas is considered to be in its normal condition when it occurs as solitary swimming cells; it occurs also as gelatinous colonies like those of Chrysocapsa. Stylochrysalis consists of O chromonas-like cells attached by a stalk at the end away from the flagella. Chrysodendron is similar but colonial, the cells attached by branched stalks. Brehmiella Pascher (1928) may occur as free-swimming Ochromonas-Vikt cells, or these may become attached by the end away from tlie flagella and develop a whorl of pseudopodia at the free end. Pseudopodia are a device for predatory nutri- tion, here occurring in an organism which is capable also of photosynthesis. Hetero- chromonas includes organisms of the structure of Ochromonas but without plastids, be- ing presumably saprophytic, and containing only a pigmented speck by which it is sup- posed that the direction of light is perceived. The historical generic name Monas O. F. Miiller, as restricted in application by scholars up to Ehrenberg and as applied ever since, designates totally non-pigmented cells, saprophytic or predatory, free- swimming like Ochromonas or attached like Stylochrysalis [Physomonas Kent desig- nates cells of Monas in the attached condition). There are believed to be several species, but the group remains poorly known. It was in some member of it that Loeffler (1889) first observed the pantoneme character of flagella. Dendromonas consists of similar cells forming colonies like those of Chrysodendron. In Cephalothamnium Stein, Monas-\ikc cells are gathered in capitate clusters on stout stalks. Anthophysis Bory is an organism which Leeuwenhoeck had described as a microscopic water plant: it consists of Monas-Vikt cells at the ends of branching stalks colored yellow by deposits of iron. The comparatively unfamiliar original spellings of the two generic names just mentioned were restored by Kudo ( 1946). The name Uvella Bory appears to represent small clusters of cells of Cephalothamnium or Anthophysis which have broken loose to swim free. Family 3. Syncryptida [Syncryptidae] Poche in Arch. Prot. 30: 156 (1913). Family Isochrysidaceae Pascher in Siisswasserfl. Deutschland 2: 43 (1913), not based on a generic name. Family Isochrysidae Calkins Biol. Prot. 262 (1926). Families Synura- ceae and Syncryptaceae Smith Freshw. Algae (1933). Ochromonas-Vike cells forming circular or globular free-swimming colonies. Flagella markedly unequal, colonies circular: Cyclonexis; colonies globular: Uroglena, Uroglenopsis. Flagella apparently equal: Syncrypta, Synura. 60 ] The Classification of Lower Organisms Family 4. Dinobryina Ehrenberg Infusionsthierchen 122 (1838). Family Dino- hryaceae Engler in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. 2: 570 (1897). Pigmented or colorless cells of the characters of Ochromonas or Monas, sheltered in loricae, that is, in transparent open shells, solitary or colonial. The pigmented examples have generally been referred to Ochromonadaceae (or whatever), the colorless to Monadidae (or whatever). Pigmented, solitary, flagella markedly unequal: Epipyxis, Stylo pyxis; flagella apparently equal: Chry so pyxis Stein {Dere- pyxis Stokes). Pigmented, forming branching colonies: Dinobryon, Hyalobryon. Poteriochromonas Scherffel resembles Stylopyxis, but the protoplast can project pseudopodia from its lorica, thus supplementing photosynthesis by predatory nutri- tion. Non-pigmented, solitary, flagella markedly unequal: Stokesiella; flagella ap- prrently equal: Diplomita. Non-pigmented cells in colonies quite of the character of those of Dinobryon: Stylobryon. Family 5. Hymenomonadacea [Hymenomonadaceae] Senn in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. la: 159 (1900). Family Coccolithophoridae Lohman in Arch. Prot. 1: 127 (1902). Family Hymenomonadidae Doflein. Family Cocco- lithidae Poche in Arch. Prot. 30: 157 (1913). Order Syracosphaerinae and family Pontosphaeraceae Schiller in Arch. Prot. 51: 8 (1925). Families Syracosphaeraceae, Halopappaceae, Deutschlandiaceae, and Coccolithaceae Kampter. Family Thora- cosphaeracee Schiller in Rabenhorst Kryptog.-Fl. Deutschland ed. 2, 10, Abt. 2: 156 (1930). Y3imi\it5 Syracosphaeridae, Calcisolenidae, Thoracosphaeridae, and Braad- rudosphaeridae Deflandre in Grasse Trait6 Zool. 1, fasc. 1: 452, 457, 458 (1952). Family Discoasteridae Tan Sin Hok. Suborder Coccolithina Hall Protozoology 130 (1953). Solitary cells with one or two brown plastids, usually with two apparently equal flagella, having a thin cell wall from which project bodies of calcium carbonate (coccoliths) of definite form. More than twenty genera and nearly 150 species have been described (Lohman; Schiller; Kamptner, 1940). Neither the number of species nor the variety of form appears to warrant making more than one family of the group. Nearly all examples are marine. In Pontosphaera, Calyptosphaera, and allied genera, the coccoliths are disks or hemispheres, sometimes umbonate and sometimes marked by one or more pits. In Syracosphaera the coccoliths, or a few of them near the insertion of the flagella, bear horn-like projections. In Najadea, Halopappus, and Calciconus, each cell bears a whorl or elongate bristles. Cells of Calcisolenia are fusiform, without flagella, with an armor of two layers of spiral bands of calcareous matter. In Hymen- omonas and Coccolithus Swartz 1894 [Coccosphaera Wallich 1877, non Perty 1852; Coccolithophora Lohman 1902) the coccoliths are punctured and accordingly ring- shaped; Hymenomonas difi"ers from most of the group in occurring in fresh water. In Discosphaera and Rhabdosphaera the punctured calcareous bodies are drawn out to the form of tubes, spools, or trumpets. These obscure organisms are not without importance. They occur in all oceans, being most abundant in gulfs, such as the Adriatic, where the salinity is diminished by rivers (Schiller, 1925). According to Bernard (1947) turbidity in the Mediter- ranean depends chiefly on this group. Coccoliths are abundant in the ooze on the bottoms of oceans. They occur as fossils as far back as the Cambrian, being par- ticularly abundant in certain Cretaceous deposits. Family 6. Phaeothamnionacea [Phaeothamnionaccae] Pascher in Siisswasserfl. Deutschland2: 113 ( 1913). Family Chrysotrichaceae Fascher (1914). Family Nema- tochrysidaceae Pascher (1925). Brown organisms, minute, marine, epiphytic, filamen- Phylum Phaeophyta [ 61 tous, reproducing by zoospores bearing paired unequal flagella. Nematochrysis, the filaments unbranched; Phaeothamnio7i, the filaments branched. These organisms are believed to represent the transition between the Chrysocapsacea and the typical brown algae. There is a family Amphimonadidae or Amphimonadaceae of unwalled colorless flagellates with paired supposedly equal flagella. They appear to belong to the kingdom of plants, in the neighborhood of Chlamydomonas and Polytoma. If, how- ever, future study shows their flagella actually to be respectively pantoneme and acroneme, they are to be placed in the present order. Order 2. Silicoflagellata Borgert in Zeit. wiss. Zool. 51: 661 (1891). Chromomonadina Klebs in Zeit. wiss. Zool. 55: 394 (1893). Order Chromomonadina Blochmann Mikr. Tierwelt ed. 2. Abt. I: 57 (1895). Subclass Chrysomonadineae Engler in Engler and Prantl Nat. Pflanzenfam. ITeil, Abt.'la: iv (1900). Order Chrysomonadales Engler Syllab. ed. 3: 7 (1903). Chrysomonadinae; Euchrysomonadinae , with order Chromulinales; Chryso- capsinae; and Rhizochrysidinae Pascher in Siisswasserfl. Deutschland Heft 2 (1913). Chrysomonadales, Chrysocapsales, Chrysosphaerales, and Chrysotrichales Pas- cher in Ber. deutschen bot. Gess. 32: 158 (1914). Order Chrysomonadina Doflein Lehrb. Prot. ed. 4: 401 (1916). Order Chrysomonadida Calkins Biol. Prot. 258 (1926). Classes Chrysomonadineae , Rhizochrysidineae, Chrysocapsineae, Chrysosphaeri- neae, and Chrysotrichineae Pascher in Beih. bot. Centralbl. 48, Abt. 2: 323 (1931). Suborders Euchrysomonadina, Silicoflagellina, Rhizochrysidina, and Chrysocap- sina Hall Protozoology 125, 128, 130, 132 (1953). Organisms of much the character of Ochromonadalea, but producing flagellate stages with a single flagellum, or not producing flagellate stages. The detailed structure of the flagella has seemingly never been determined. Statospores are known to be produced by Chromulina, Mallonionas, and (of somewhat exceptional charac- ter) by Hy drums. Sexual reproduction has not been observed. Mitosis, with an intranuclear spindle and numerous chromosomes, was observed by Doflein (1916) in Rhizochrysis. This order is supposed to represent the direct ancestry of orders Choanoflagellata and Hyphochytrialea. 1. Neither amoeboid nor truly filamentous. 2. Not flagellate in the vegetative condi- tion. 3. Microscopic colonies Family 1. Chrysosphaeracea. 3. Macroscopic gelatinous colonies simulating filaments Family 2. Hydruragea. 2. Flagellate in the vegetative condition. 3. Without prominent siliceous struc- tures Family 3. Chrysomonadina. 3. With siliceous scales usually bearing bristles Family 4. Mallomonadinea. 3. With siliceous internal skeletons Family 5. Actiniscea. 62 ] The Classification of Lower Organisms 1. Amoeboid Family 6. Chrysamoebida. 1. Filamentous Family 7. Thallochrysidacea. Family 1. Chrysosphaeracea [Chr>'Sosphaeraceae] Pascher in Arch. Prot. 52: 562 (1925). Family Naegelliellaceae Pascher op. cit. 561. Family Nagelliellidae Hall Protozoology 133 (1953). Non-motile brown cells, either capable of repeated division into two, thus forming aggregates of indefinite number, or else undergoing multiple division and producing colonies of definite number of cells; mostly known to produce uniflagellate zoospores. Chrysosphaera, Epichrysis, Chrysospora, Gloeochrysis, Nae- gelliella, and other genera. Family 2. Hydruracea [Hydruraceae] West British Freshw. Algae 45 (1904). Hydrurina Klebs in Zeit. wiss. Zool. 55: 420 (1893). Family Hydruridae Poche in Arch. Prot. 30: 158 (1913). Like Chrysosphaeracea, but the colonies dendroid, growing at the tips, becoming macroscopic; producing tetrahedral zoospores and spheroidal resting cells bearing a unilateral crest. Hydrurus foetidus, in mountain streams. Family 3. Chrysomonadina Stein Org. Inf. 3, I Halfte: x (1878). Family Chrysomonadidac Kent Man. Inf. (1880). Family Chromulinaceae Engler in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. 2: 570 (1897). Family Chromulinidae Doflein. Brown flagellates with a single anterior flagellum, sometimes producing siliceous granules but without more extensive siliceous structures. Free-swimming, walled: Chrysococcus, Microglena. Naked: Chromulina, the type genus of Chryso- monadina, the generic name Chrysomonas being a synonym. Organisms of this genus are rather freely capable of producing pseudopodia and supplementing photosynthetic nutrition by predatism, or, alternatively, of producing gelatinous aggregates of walled non-motile cells (Hofender, 1913; Gicklhom, 1922). Chrysapsis differs from Chromulina in having in each cell a single plastid in the form of a network. Solitary attached cells, producing pseudopodia only occasionally: Lepo chromulina. Bearing whorls of permanent pseudopodia: Cyrtophora, Pedinella, Palatinella (Pascher, 1928). Family 4. Mallomonadinea Diesing in Sitzber. Akad. Wiss. Wien Math.-Nat. CI. 52, Abt. 1: 304 (1866). Family Mallomonadidae Kent (1880). Brown uniflagellate free-swimming cells with an armor of siliceous scales usually bearing bristles. Mallo- m.onas, solitary cells, the bristle-bearing scales circular. Conradiella, the scales of the form of rings about the body. Chrysosphaerella, spherical colonies, each cell with two long bristles. Family 5. Actiniscea [Actinisceae] Kiitzing Phyc. Germ 117 (1845). Family Dictyochidae Wallich. Class Silicoflagellata (Borgert), orders Siphonotestales and Stereotestales, and families Dictyochaceae and Ebriaccae Lemmermann in Ber. deutschen bot. Gcss. 19: 254-268 ( 1901 ). Division (?) Silicoflagellatac Engler. Family SiHcoflagellidae Calkins Biol. Prot. 263 (1926). Famihes Ebriopsidae, Ditripodiidae, Ammodochidae, and Ebriidae Deflandre in Grasse Traite Zool. 1, fasc. 1: 421, 423, 424 (1952). Solitary brown uniflagellate cells with a continuous internal skeleton of silica. Marine, commonest in colder oceans. The skeletons are not subject to decay and are found as micro fossils in chalk and diatomaceous earth. They have been reported from the Silurian and are com- monest in certain Cretaceous deposits. Ehrcnbcrg described several fossil species, classifying them as diatoms. The living forms, subsequently discovered, include apparently the same species. Gemeinhardt (in Rabcnhorst, 1930) accounted for the structure of the cells. Phylum Phaeophyta [ 63 They are approximately of radial symmetry, the axis being shorter than the diameter. The skeleton is completely imbedded in protoplasm. It may be a mere ring; or the ring may bear radially projecting spines; or it may be the margin of a more or less complicated basket-shaped network coaxial with the cell. Numerous brown plastids lie near the surface of the protoplast. There is no cell wall. The double cells, like two cells lying face to face, which have occasionally been seen, are not stages of conjugation, but of cell division, in which one daughter cell retains the original skeleton while the other develops a new skeleton in the position of a mirror image of the original one. Lemmermann and Gemeinhardt accounted for only six genera and twenty-four species, but Gemeinhardt recognized numerous varieties, and it is probable that the number of species has been underestimated. Mesocaena, the skeleton a mere ring, smooth or spiny; Dictyocha, Distephanus, Cannopilus, the skeleton more or less netted. Family 6. Chrysamoebida [Chrysamoebidae] Poche in Arch. Prot. 30: 157 (1913). Families Rhizochrysidaceae , Chrysarachniaceae, and Myxochrysidaceae Pascher in Beih. Bot. Centralbl. 48, Abt. 2: 323 (1931). Family Rhizochrysididae Hollande in Grasse Traite Zool. 1, fasc. 1: 547 (1952). Families Rhizochrysidae and Myxochry- sidae Hall Protozoology 130, 132 (1953). Amoeboid organisms with brown plastids of the form of one or two parietal films in each cell. Rhizaster, an attached organism resembling Cyrtophora and Pedinella but lacking the flagellum. Chrysocrinus, at- tached to algae, the protoplast covered by a dome-shaped shell punctured by many pores through which project the slender psudopodia. Chrysamoeba, a freely moving cell usually with one flagellum; Rhizochrysis, similar, without the flagellum. Myxo- chrysis, a large multinucleate form. Chrysarachnion, the cells clustered and linked together by strands of protoplasm. Lagynion, having an attached vase-shaped lorica from which projects usually a single slender pseudopodium. Chrysothylakion, with a retort-shaped lorica from which project many slender pseudopodia, branching and anastomosing. Only the plastids distinguish these organisms from various genera classified as Rhizopoda, Heliozoa, or Sarkodina. Family 7. Thallochrysidacea [Thallochrysidaceae] Pascher (1925). Brown or- ganisms producing definite filaments of walled cells and reproducing by anteriorly uniflagellate zoospores. T hall ochry sis. Phaeodermatium. Order 3. Vaucheriacea [Vaucheriaceae] Nageli Gatt. einzell. Alg. 40 (1849). Class Heterokontae and orders Chloromonadales and Confervales Luther in Bihang Svensk. Vetensk.-Akad. Handl. 24, part 3, no. 13: 19 (1899). Not Chloromonadina Klebs (1893); not order Confervoidea C. Agardh (1824). Vaucheriales Bohlin Grona Algernas 25 (1901). Order Vaucheriales Clements Gen. Fung. 14 (1909). Orders Heterochloridales, Heterocapsales, Heterococcales, Heterotrichales, and H eter osiphonales Va.s.ch.tr mlitdwigizbZ: 10-21 (1912). Division Heterokontae, Classes Heterochloridineae, Rhizochloridineae, Hetero- capsineae, Heterococcineae, Heterotrichineae , and Heterosiphoneae, and or- ders Rhizochloridales and Botrydiales Pascher in Beih. bot. Centralbl. 48, Abt. 2: 324 (1931). Class Xanthomonadina with orders Heterochloridea and Rhizo chloride a De- flandre in Grasse Traite Zool. 1, fasc. 1: 212, 217, 220 (1952). Order Heterochlorida Hall Protozoology 133 (1953). 64] The Classification of Lower Organisms Organisms producing motile cells with paired unequal flagella which Vlk (1931) found to be respectively pantoneme and acroneme, differing from Ochromonadalea in being of a green or yellow-green color, and in being mostly of algal body type, i. e., walled and non-motile. The cell wall consists usually of two parts which become separate when the cell divides; the two parts are believed to be distantly homologous with the wall and pRig of the statospores of Ochromonadalea and Silicoflagellata (Pascher, 1932). The storage products are oil and sometimes leucosin. As this is the group to which the class name Heterokontae was first applied, it is f-'^y-'v'^^^; ■■■• >i%'X°-^'^^ Fig. 10. — Vaucheriacea: a, b^ Chlorosaccus fluidus, cells of the colony and zoo- spores, after Luther (1899). c, d^ Chlorarnoeba heteromorpha x 1,000 after Bohlin (1897). e, f, g. Cell, empty cell, and zoospores of Characiopsis gibba x 1,000 after Pascher (1912). h, Dioxys Incus after Pascher (1932). i, j, k, Cell, edge of cell, and statospore of Pseudotetraedron neglectum x 1,000 after Pascher (1912). 1, Spi- rodiscus fulvus x 1,000. m. End of a filament of Tribonema bombycina x 1,000. n, Antheridium and oogonia of Vaucheria Gardneri x 100. o. Filament of Vaucheria sessilis x 100. Phylum Phaeophyta [ 65 the type group of the class. As established by Luther, the class consisted of the new genus Chlorosaccus together with a few genera of flagellates ( Vacuolaria was included in error) and a few transferred from the group of typical green algae. From time to time, other green algae have been transferred, and it has become evident that the group is a fairly extensive one. Green organisms can be recognized as belonging here by a negative reaction to the iodine test for starch, and by the fact that they give a b'uish color when heated with hydrochloric acid, instead of a yellow one, as typical green algae do: the difference depends upon differences in the complement of photosynthetic pigments. Bohlin (1901) placed Vaucheria here; most authors have not followed him, but Smith (1950) has done so. This genus brings with itself the oldest name for the group as an order. Mitosis in Vaucheria was described by Hanatschek (1932) and Gross (1937). The spindle is intranuclear; Hanatschek saw centrosomes at the poles. The conjugation of equal free-swimming gametes was observed in Tribonema and several other genera by ScherfFel (1901), and in Botrydium by Rosenberg (1930). Vaucheria was one of the organisms by study of which the nature of fertilization was discovered (Pringsheim, 1855). Hanatschek and Gross found that the first two divisions of the nucleus of the zygote are meiotic: the soma is haploid. This order is believed to represent the direct ancestry of the two following classes, Bacillariacea and Oomycetes. Pascher (1912, 1925) arranged the green Heterokonta in subordinate groups parallel to those of the typical green algae; and, as the main groups of green algae are treated as orders, he treated these groups also as orders (in 1931 as classes). They are scarcely entitled to such rank: too many of the classes or orders are of single families, and too many of the families are of one or two genera. Here, then, Pascher's classes and orders are suppressed and several of his families are reduced. 1. Not truly filamentous nor producing rhizoids. 2. The cells walled. 3. Cells regularly dividing into two, forming gelatinous colonies; occa- sionally producing small numbers of zoospores. 4. The colonies globular or Irreg- ular, becoming macroscopic Family 1. Chlorosagcacea. 4. The colonies dendroid, micro- scopic Family 2. Mischococgacea. 3. Cells normally undergoing division into several. 4. Producing zoospores Family 3. Chlorotheciacea. 4. Producing no motile cells Family 4. Botryococcagea. 2. The cells loricate Family 5. Stipitogogcacea. 2. The cells amoeboid Family 6. Chloramoebacea. 1. Filaments of uninucleate cells Family 7. Tribonematagea. 1. Cells becoming highly multinucleate, form- ing filaments or at least producing rhizoids Family 8. Phyllosiphonacea. Family 1. Chlorosaccacea [Chlorosaccaceae] Smith Freshw. Algae 145 (1933). Family Heterocapsaceae Pascher in Hedwigia 53: 13 (1912); there is no correspond- ing generic name. Gelatinous aggregates of cells which may divide, causing the 66] The Classification of Lower Organisms aggregate to grow to macroscopic dimensions; or may produce one, two, or four zoospores. Chlorosaccus Luther, the standard genus of class Heterokonta. Family 2. Mischococcacea [Mischococcaceae] Pascher in Hedwigia 53 : 14 ( 1912). Microscopic colonies of globular cells joined by dichotomously branching gelatinous strands. Mischococcus. Family 3. Chlorotheciacea [Chlorotheciaceae] Luther in Bihang Svensk. Vetensk- Akad. Handl. 24, part 3, no. 13: 19 (1899). Families Chlorobotrydiaceae and Sci- adiaccae Pascher in Hedwigia 53: 17 (1912). Family Halosphaeraceae Pascher (1925). Family Ophiocytiaceae Auctt. Cells solitary, free or attached, capable of reproduction by division to form multiple zoospores, in some examples capable alternatively of producing multiple minute non-motile cells of the same form as the parent. Large free multinucleate cells, more or less globular: Botrydiopsis, Leu- venia. Smaller cells, elongate, curved or coiled: Characiopsis, Spirodiscus. Spirodiscus fuluus Ehrenberg in Abh. Akad. Wiss. Berlin 1830: 65 (1832) {nomen nudum) and Infusionsthierchen 86 (1838), whose identity has been a standing puzzle to bac- teriological systematists, is an older name of Ophiocytium parvidum (Perty) A. Braun (Copeland, 1954). It antedates the generic name Ophiocytium Nageli (1849); new combinations are required for the dozen additional species of this genus. The cells attached: some species of Characiopsis; Perionella; Dioxys. Family 4. Botryococcacea [Botryococcaceae] Pascher in Hedwigia 53: 13 (1912). Solitary or colonial cells reproducing strictly by production of non-motile cells. Botryococcus. Pseudotetraedron. Family 5. Stipitococcacea [Stipitococcaceae] Pascher in Beih. bot. Centralbl. 48, Abt. 2: 324 (1931). Family Stipitochioridae Deflandre in Grasse Trate Zool. 1, fasc. 1: 221 (1952). Amoeboid cells with green plastids, partially enclosed in loricae at- tached to objects in water. Stipitococcus. Family 6. Chloramoebacea [Chloramoebaceae] Luther in Bihang Svensk. Vetensk.- Akad. Handl. 24, part 3, no. 13: 19 (1899). Family Chloramoebidae Poche in Arch. Prot. 30: 155 (1913). Families Heterochloridaceae and Rhizochloridaceae Pascher Siisswasserfl. Deutschland 11: 22, 26 (1925). Y^.miWts Heterochloridae, Rhizochlori- dae, Chlorarachnidae and Myxochloridae Deflandre in Grasse Traite Zool. 1, fasc. 1 : 217-222 (1952). Amoeboid organisms with green plastids, without loricae, some- times swimming by means of paired unequal flagella. Chloramoeba, Chlorochromo- nas, Rhizochloris. Family 7. Tribonematacea [Tribonemataceae] Pascher in Hedwigia 53 : 19 ( 1912) . Family Confervaceae Luther (1899). Family Monociliaceae Smith Freshw. Algae 160 (1933). Green Heterokonta producing filaments of uninucleate cells. The Lin- naean genus Conferva included a great variety of growths in water. Definite groups were separated from it, one after another, until the residue was a natural group; but this residue cannot be assumed to be the type of Conferva L.; that name is to be abandoned as a nomen confusum. The remnant in question has become two genera, Tribonema Derbes and Solier, 1858, and Bumilleria Borzi, 1895. They are unbranched filaments, common in freshwater pools. From typical green algae of similar appear- ance they are distinguished in the first place by the presence in each cell of several disk-shaped plastids without pyrenoids or with obscure ones. The cell walls, when treated with sulfuric acid, can be seen to consist of two parts like a barrel sawed across the middle. A broken filament ends always with a broken half wall. Monocilia, an unfamiliar alga isolated from soil, difi^ers in producing branching filaments. Phylum Phaeophyta [ 67 Family 8. Phyllosiphonacea [Phyllosiphonaceae] Wille in Engler and Prantl. Nat. Pflanzenfam. I Teil, Abt. 2: 125 (1890). Family Vaucheriaceae (Nageli) Areschoug (1850), preoccupied by order Vaucheriaceae Nageli. Family Botrydiaceae Luther (1899). Heterokonta whose bodies are highly multinucleate single cells, filamentous or anchored by filamentous rhizoids. Botrydium is found on damp soil as dark green globes, sometimes as much as 2 mm. in diameter, anchored by much-branched color- less rhizoids. Vaucheria is a familiar alga on damp earth or in fresh water. It consists of irregularly branching filaments, green where exposed to light, colorless where growing downward and serving as rhizoids. The reproductive cells are cut off by walls. The end of an aerial filament, cut off in this fashion, may as a whole act as a spore. In water, the protoplast of such a cell may escape as an exceptionally large zoospore with as many pairs of flagella as the nuclei within it. Antheridia are brief branches, each releasing many minute sperms each with two unequal flagella. Oogonia are globular cells, multinucleate during development, but containing only one functional nucleus when mature. Phyllosiphon is of much the same structure as Vaucheria, but is parasitic in seed plants, particularly Araceae. It reproduces, ap- parently, only by the breaking up of the protoplast to produce minute non-flagellate spores. Order 4. ChoanoflageUata [Choano-Flagellata] Kent Man. Inf. 1: 36 (1880). Order Bicoecidea Grasse and Deflandre in Grasse Traite Zool. 1, fasc. 1: 599 (1952). Non-pigmented flagellates, usually attached, each cell bearing a single flagellum of the type called pantacroneme, with lateral appendages and a terminal whip-lash; the cell bearing also a protoplasmic collar, usually surrounding the base of the flagel- lum. The collar is a means of nutrition. Bacteria and other scraps of organic matter, driven against it by the beating of the flagellum, adhere and are carried to the interior of the cell by flow of the cytoplasm of which it consists. It is probable that the pantacroneme flagellum is a variant of the pantoneme flagellum, and that this order belongs naturally in class Heterokonta. It may have evolved from Silicoflagellata; or it may be that the collar is a modified flagellum, and that the group evolved from order Ochromonadalea. Most authors have recognized more than one family of choanoflagellates, but genera are not very numerous and one family seems sufficient to accommodate them. Family Bicoekida Stein Org. Inf. 3, I Halfte: x (1878). Family Craspedornona- dina Stein 1. c. Families Bikoecidae, Codonosigidae, Salpingoecidac, and Phalansteri- idae Kent op. cit. Families Codonoecina and Bikoecina Biitschli in Bronn Kl. u. Ord. Thierreichs 1: 814, 815 (1884). Families Bicoecaceae, Craspedoynonadaceae, and Phalanasteriaceae Senn in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. la: 121, 123, 129 (1900). Family Gymnocraspedidae Grasse Traite Zool. 1, fasc. 1: 590 (1952). Characters of the order. Cells naked, solitary: Monosiga; colonial: Codo- siga James-Clark [Codonosiga Stein), Sphaeroeca. Cells imbedded in gelatinous matter, the collars contracted: Phalanseterium. Loricate: Salpingoeca, Bicosoeca, Poteriodendron. The choanoflagellates were discovered by James-Clark (1866, 1868), who made at the same time the discovery that certain internal cavities of sponges are lined by minute cells (choanocytes) of the same structure as the choanoflagellates. From these observations he drew the conclusion that sponges are a sort of flagellates dis- tinguished by the production of exceptionally large and elaborate colonies. Kent 68] The Classification of Lower Organisms described Proterospongia Haeckeli as a colonial organism of amoeboid and choano- flagellate cells in a common matrix; he regarded it as a transitional form, important as evidence of the evolution of sponges from choanoflagellates. According to Duboscq and Tuzet ( 1937) it is no organism, but a stage in the development of an individual sponge from one which has been damaged. In spite of this, the hypothesis that the choanoflagellates represent the evolutionary origin of the sponges, and accordingly of the entire animal kingdom, continues to appear tenable. Fig. 11. — Choanoflagellata : a, b, Monosiga spp.; c^ Phalanasterium digitatum; A, Salpingoeca ampullacea; e, Salpingoeca Clarkii; i, Foteriodendron petiolatum. c X 500, the remainder x 1,000. c-f after Stein (1878). Phylum Phaeophyta [ 69 Order 5. Hyphochytrialea [Hyphochytriales] Bessey Morph. and Tax. Fungi 69 (1950). Order Anisochytridiales Karling in American Jour. Bot. 30: 641 (1943), not based on a generic name. Non-pigmented organisms with walled cells, parasitic or saprophytic, the proto- plasm with numerous granules not of a shining appearance, producing zoospores with single anterior pantoneme flagella. The naked zoospores come to rest upon appropriate hosts or substrata. Ordinarily, in parasitic species, the protoplast of the zoospore makes its way to the interior of a cell of the host. It swells and develops a thin wall. The resulting structure may be called a center. In most members of the group, the center gives rise to a system of slender rhizoids; in some species, these give rise to further centers like the original one. Karling studied the cytology particularly in Anisolpidium. There are repeated simultaneous mitoses in the growing centers. Resting nuclei contain conspicuous karyosomes. Dividing ones show about five chromosomes in an intranuclear spindle which ends sharply in centrosomes. Eventually, in the usual course of events, each center produces an exit tube to the exterior. Its contents are released by delique- scence of the tip of the exit tube. Either before this or afterward, the mass of proto- plasm undergoes cleavage into uninucleate protoplasts which generate flagella. Some- times, instead of discharging their contents, the centers are converted into resting spores by the secretion of thick walls (this has been observed in only a few of the species). The resting spores germinate by producing exit tubes and discharging zoospores as ordinary centers do. The body type which has just been described may be called the chytrid body type; organisms of this body type were formerly assembled as a taxonomic group typified by the genus Chytridium. Couch, however, showed that these organisms form three groups distinguished by fundamental differences in type of flagellation. The present group is here given a place implying relationship to order Silicoflagellata. Karling (1943) accounted for fourteen species. He provided three families; only one is here maintained. Family Hyphochytriacea [Hyphochytriaceae] Fischer in Rabenhorst Kryptog.-Fl. Deutschland 1, Abt. 4:131 (1892). Families Anisolpidiaceae and Rhizidiomycetaceae Kailing in American Jour. Bot. 30: 641, 643 (1943). Characters of the order. Without rhizoids: Anisolpidium on brown algae; Roesia on Lemna; Cystochytrium on roots of Veronica. With rhizoids from a single center: Rhizidiomyces and Latr os- tium on green algae, aquatic fungi, and the empty exoskeletons of insects. With multiple centers: Hyphochytrium and Catenariopsis, on fungi and other hosts. Class 2. BACILLARIACEA Engler and PrantI Homalogonata Lyngbye Tent. Hydrog. Danicae 177 (1819). Order Diatomeae C. Agardh Syst. Alg. xii (1824). Division (of order ^/gae) Diatomaceae Harvey in Mackay Fl. Hibem. 166 (1836). Family Bacillaria Ehrenberg Infusionsthierchen 136 (1838). Series (of class Algae) Diatomaceae Harvey Man. British Alg. 15 (1841). Abtheilung (of cldiS,?, Isocarpeae) Diatomaceae Kiitzing Phyc. Germ. 54 (1845). Stamm Diatomea Haeckel Gen. Morph. 2: xxv (1866). Division (of class Algae) Diatomaceae Rabenhorst Kryptog.-Fl. Sachsen 1: 1 (1863). 70] The Classification of Lower Organisms Fig. 12. — Hyphochytrialea: a-e^ Anisolpidium Ectocarpii; a-c, individuals de- veloping in cells of Ectocarpus; d, mitotic figures x 2,000; e^ cell of Ectocarpus filled by a mature individual discharging spores, f, g, Rhizidiomyccs apuphysatus; f, zoo- spore; g, oogonium of Achlya parasitized by three individuals, h, i, j^ llyphochy- trium catenoides; h, zoospore; i, young individual; j, mature individual with fila- ments, sporangia, and zoospores in various stages of development. All after Karling (1943, 1944, 1939). x 1,000 except as noted. Phylum Phaeophyta [71 Class Bacillariaceae Engler and Prantl Nat. Pflanzenfam. II Teil; 1 (1889). Subdivision and class Bacillariales Engler Syllab. 6 (1892). Hauptclasse Diatomeae Haeckel Syst. Phylog. 1: 90 (1894). Subclass Bacillariales Engler in Engler and Prantl Nat. Pflanzenfam. Teil I, Abt. la: V (1900). Class Bacillarieae Wettstein Handb. syst. Bot. 1: 74 (1901). Class Bacillarioideae Bessey in Univ. Nebraska Studies 7: 283 (1907). Class Diatomeae Schaffner in Ohio Naturalist 9: 447 (1909). Abteilung Bacillariophyta Engler. Ahteilung (of Stamm Chrysophyta) Diatomeae Pascher in Beih. bot. Centralbl. 48, Abt. 2: 324 (1931). Class Bacillariophyceae Auctt. Unicellular (occasionally filamentous or colonial) organisms without flagella in the vegetative condition, each cell with one, two, or more plastids, brown, varying to yellow or exceptionally to bluish or colorless, and bearing a siliceous shell of two parts. Globules of oil and granules of something called volutin (the "red granules of Biitschli," apparently protein) are present. Other granules in some examples are said to be of leucosin. These organisms, the diatoms, are very common. There are some 5300 species. Microscopic examination of the bottoms of fresh water ponds reveals usually more of diatoms than of any other kind of organisms. Diatoms are frequent prey of many kinds of predators, from amoebas to whales. In using fish-liver oils as a source of vitamin D, man adds himself to a long chain of predators of which it is believed that diatoms are the usual ultimate prey. The shells of diatoms are not subject to decay. In certain places which were in the geologic past arms of the sea, there are enormous deposits of diatom shells in the form of a white earth. The oldest deposits are of the Cretaceous age. Thus it ap- pears that diatoms are a modern offshoot, no more ancient than the flowering plants. Diatomaceous earth is mined for various uses. It is an effective insulating material, and was the inert material first used in connection with nitroglycerine in the manu- facture of dynamite. The two parts of the shell of a diatom are called valves. They fit one over the other "like the parts of a pill box" (ZoBell, 1941, objects to this traditional simile, on the ground that in current language a pillbox is a concrete structure with loop- holes). The shells consist basically of something of the nature of pectin heavily im- pregnated with silica and characteristically sculptured. The cells appear markedly different in different aspects: the aspect which is in effect top or bottom view is called valve view, and that which is in effect side view is called girdle view. When a cell divides, each of the daughter cells receives one of the valves and generates an additional valve fitting within it. Diatoms in culture undergo a gradual diminution in size; there is an old hypothesis that this is caused by the fact that one of each pair of sister cells receives a slighly smaller valve than the other. Lauterborn (1896) described mitosis in Surirella and other diatoms. He found a centrosome, with radiating strands, near the nucleus. At the beginning of mitosis, the centrosome generates a disk-shaped structure which enters the nucleus and grows in such fashion as to become a cylinder extending through it. The cylinder is recog- nizably a spindle, but the chromosomes, instead of appearing within it, form a ring- shaped mass about its middle and divide into two ring-shaped masses which move along it to its extremities. The nuclear membrane ceases to be recognizable early in The Classification of Lower Organisms Fig. 13. — Bacillariacea : a, Mclosira sp., a living cell and an empty one. b, c. Girdle and valve views of cell of Cyclotella sp. d, e. Sections of a valve of Pinnu- laria sp., highly magnified, after Otto Miillcr (1896); d, about half-way between the middle and the end, e^ near the end. f, g, Girdle and valve views of Synedra sp. h, i. Girdle and valve views of Rhoicosphenia curvata. j, k, Girdle and valve views of Navicula sp. 1^ m, Girdle and valve views of Gomphonema sp. (the former show- ing the gelatinous stalk by which the cell is attached), n, o. Girdle and valve views of Cymbella sp. p, q, Surirella saxonica after Karsten (1900); p, two cells joined before conjugation; q, zygote; x 250. r, s, Girdle and valve views of Cocconeis sp. X 1,000 except as noted. Phylum Phaeophyta [ 73 the process, but the nuclear cavity remains distinct until the chromosomes have reached the ends of the spindle. The nuclear sap and the spindle are then absorbed by the cytoplasm, but not until the spindle has budded off a new centrosome from each end. Subsequent authors, as Karsten (1900), Geitler (1927), Iyengar and Subrahman- yan (1942, 1944), and Subrahmanyan (1947), have not seen as full a series of stages as Lauterbom did. They have found centrosomes in at least some diatoms, and have confirmed the point that the spindle is a cylinder which is surrounded by the chromosomes instead of including them. The same authors have described sexual processes in Surirella, Cymbella, Coc- coneis, Cyclotella, and Navicula. In Surirella saxonica as described by Karsten, pairs of the wedge-shaped cells become attached by little bodies of slime at the narrow ends. Each nucleus divides twice, producing four, of which three are digested by the cytoplasm. The two protoplasts then move in amoeboid fashion out of their shells and they and their nuclei unite. The zygote protoplast grows to a size much greater than that of the parent cells and secretes a membrane which becomes silicified. The resulting cell is called an auxospore. In most kinds of diatoms, each cell produces two gametes. In some, the cells pair and proceed to produce auxospores individually, without conjugation. Karsten sup- sposed the latter examples to represent a stage in the evolution of sexual reproduc- tion under some zwingender Nothwendigkeit: much more probably, they are pro- ducts of degeneration. In Cyclotella, Iyengar and Subrahmanyan found the produc- tion of auxospores to involve autogamous karyogamy: the nucleus of a solitary cell undergoes meiosis; two of the haploid nuclei are digested, and the two which remain fuse with each other. It is evident that all diatoms are diploid in the vegetative condition. The filamentous green Heterokonta Tribonema and Bumilleria are closely similar to the diatom Melosira, and it may reasonably be supposed that they represent the evolutionary origin of the group. Diatoms are preserved for study by violent methods which destroy the protoplasts, and the classification is based strictly on characters of the shells. So uniform is the group that Schiitt (in Engler and Prantl, 1896) treated it as a single family. He pro- vided an elaborate subsidiary classification involving two main groups. Subsequent scholars have found his system essentially sound as a representation of nature, but have raised the main groups to the rank of orders and the minor ones in correspond- ing degree. Order 1. Disciformia [Disciformes] Kiitzing Phyc. Germ. 112 (1845). Order Appendiculatae Kiitzing 1. c. Centricae Schiitt in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. lb: 57 (1896). Order Centricae Campbell Univ. Textb. Bot. 90 (1902). Order Eupodiscales Bessey in Univ. Nebraska Studies 7: 284 (1907). Diatoms basically of radial symmetry, which, however, is often distorted; not motile in the vegetative condition; plastids numerous in the cells. These are the more primitive diatoms. The majority are marine. Three types of reproductive cells are known to be produced by them. Occasionally, in mass catches of material from the ocean, diatoms are found whose protoplasts have undergone repeated division within the shell and produced 74 ] The Classification of Lower Organisms numerous little naked protoplasts. These protoplasts are said to bear flagella; whether one or two, equal or unequal, is not certainly known. They are supposed to escape and function as zoospores, but Karsten (1904), on rather scant evidence, supposed them to be gametes. A protoplast may contract and form a shell within its former shell. The new shell consists like the old one of two parts, one fitting within the other. The outer shell is usually more or less elaborately sculptured, while the inner is smooth. It is supposed that the outer shell is deposited between outer and inner masses of protoplasm, and that the entire protoplast then withdraws to the interior and deposits the inner shell in the opening. It is in this manner that the statospores of chrysomonads are formed. The resting cells of diatoms as just described are believed to be homologous with them, and are called by the same term. As a third manner of producing a reproductive cell, a protoplast may expand, force apart the valves of its shell, and deposit an enlarged shell about itself. The resulting spore is called an auxospore. As noted, Iyengar and Subrahmanyan found the pro- duction of auxospores in Cyclotclla to involve sexual processes. Schiitt divided the Centricae into three groups with names in -oideae (presum- ably subfamilies) and these into nine groups with names in -eae (presumably tribes). Subsequent authorities have made of Schiitt's groups a varying number of families. The minimum tenable number of families is three, corresponding to Schutt's subfamilies. Family 1. Coscinodiscea [Coscinodisceae] Kiitzing Phyc. Germ. 112 (1845). Family Melosireae Kiitzing op. cit. 66. Families Melosiraceae and Coscinodiscaceae West British Freshw. Alg. 274, 276 (1904). Melosira, in fresh water, the shells feebly silicified, the cells joined end to end in filaments. Cyclotclla, separate drum-shaped cells in fresh water. Coscinodiscus, the cells disk-shaped. Triceratium, cells of the form of 3-, 4-, or 5-sided prisms with abbreviated axes. Family 2. Rhizosoleniacea [Rhizosoleniaceae] West British Freshw. Alg. 278 (1904). The cells, circular or elliptic in cross section, becoming elongate by inter- calation of ring-shaped bands of wall between the valves. Rhizosolenia. Corethron. Family 3. Biddulphiea [Biddulphieae] Kutzing Phyc. Germ. 115 (1845). Families Biddulphiaceae and Chaetoceraceae Auctt. Cells laterally compressed, elliptic in valve view, oblong or rhombic in girdle view. Cells of Biddulphia, solitary or colonial, are familar as epiphytes on marine algae. Chaetoceros, the cells with a long spine at each corner, frequently united valve to valve in filaments, abundant in subpolar oceans. Order 2. Diatomea [Diatomeae] C. Agardh Syst. Alg. xii (1824). Tribe Striatae with orders Astomaticae and Stomaticae, and tribe Vittatae also with orders Astomaticae and Stomaticae, Kutzing Phyc. Germ. ( 1845). Pennatae Schiitt in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. lb: 101 (1896). Order Pennatae Campbell Univ. Textb. Bot. 90 ( 1902). Order Naviculales Bessey in Univ. Nebraska Studies 7: 284 ( 1907). Diatoms basically of isobilateral symmetry, occasionally so skewed as to be dorsi- ventral or asymmetric; valves usually punctured by a longitudinal cleft called the raphe, or bearing a marking of some sort, called the pseudoraphe, in the same posi- tion; exhibiting, when possessed of a true raphe, a gliding motion; cells usually with two plastids. Phylum Phaeophyta [ 75 The motion of the pennate diatoms is a gliding upon surfaces, with frequent re- versal, in either direction of the long axis of the cell. It depends upon the flow of a stream of exposed protoplasm. This is the opinion of Max Schultze (1865), Otto Miiller (1889, 1896), and Lauterborn (1896); there have been other hypotheses. Miiller showed that the true raphe, without which the motion does not occur, is an actual opening. The raphe is not a simple crack; it enters the wall obliquely and bends at a sharp angle to come from another oblique direction to the interior. Its proportions vary along its length, and it is interrupted at the middle of the valve by a knob, the central granule, projecting inward from the valve. The pennate diatoms do not produce flagellate cells nor statospores, but they pro- duce auxospores, usually by sexual processes. The majority inhabit fresh water. Eleven families are currently recognized. a. Without raphes. Family 1. Fragilariea [Fragilarieae] (Harvey) Kutzing Phyc. Germ. 62 (1845). Family Fragilariaceae West British Freshw. Alg. 285 (1904). Cells symmetrical with respect to three planes, without internal partitions. Fragilaria. Synedra. Family 2. Tabellariea [Tabellarieae] Kutzing op. cit. 110. Family Tahellariaceae West op. cit. 281. Cells symmetrical with respect to three planes, with longitudinal internal partitions. Tabellaria. Family 3. Bacillaria Ehrenberg Infusionsthierchen 136 (1838). Family Diato- maceae West op. cit. 284. Cells symmetrical with regard to three planes, with trans- verse internal partitions, solitary, or joined valve to valve in ribbons, or corner to comer in zig-zag chains. Diatoma. Family 4. Meridiea [Meridieae] Kutzing op. cit. 61. Family Meridionaceae West op. cit. 283. Cells symmetrical with regard to two planes, wedge-shaped both in valve and in girdle view, with transverse internal partitions, often joined valve to valve in fan-shaped colonies which are sometimes so extended as to produce spiral fila- ments. Meridion. b. With raphes, the valves of each cell alike. Family 5. Naviculea [Naviculeae] Kiitzing op. cit. 90. Family Naviculaceae Rab- enhorst Kryptog.-Fl. Sachsen 1: 33 (1863). This is the most numerous family of diatoms. In most of the genera the cells are narrowly rectangular in girdle view, narrowly elliptic in valve view, being of the shape of flat-bottomed boats. Navicula, Pinnularia, etc. In other genera, as Gyrosigma and Pleurosigma, the cells are so skewed as to be sigmoid in valve view. Family 6. Gomphonemea [Gomphonemeae] Kiitzing op. cit. 87. Family Gom- phonemaceae West op. cit. 297. Cells wedge-shaped. Gomphonema. Family 7. Cymbellea [Cymbelleae] (Harvey) Kiitzing op. cit. 84. Family Cocco- nemaceae West op. cit. 298. Cells with two planes of symmetry, in valve view crescent- shaped or approximately so. Cymbella. Rhopalodia. Family 8. Eunotiea [Eunotieae] Kiitzing op. cit. 57. Family Eunotiaceae West op. cit. 287. Cells curved as in the preceding family, the raphes reduced to brief clefts near the ends of the valves. Eunotia. Family 9. Nitzschiacea [Nitzschiaceae] West op. cit. 301. Cells asymmetric in valve view, the raphe along one margin. Nitzschia. Hantschia. Family 10. Surirellea [Surirelleae] Kiitzing op. cit. 70. Family Surirellaceae West op. cit. 303. Each cell with two marginal raphes. Surirella. c. The two valves of each cell unlike, one with a raphe, one with a pseudoraphe. 76 ] The Classification of Lower Organisms Family 11. Achnanthea [Achnantheae] Kiitzing op. cit. 81. Families Achnan- thaceae and Cocconeidaceae West op. cit. 289, 290. Achnanthes, Rhoicosphenia, Cocconeis. Class 3. OOMYCETES Winter Class OoMYCETEs Winter in Rabenhorst Kryptog.-Fl. Deutschland 1, Abt. 1: 32 (1879). Phycomyceten de Bary Vergl. Morph. Pilze 142 ( 1884), in part. Class Phycojnycetes Engler and Prantl Nat. Pflanzenfam. II Teil: 1 (1889), in part. Reihe Oomycetes Fischer in Rabenhorst Kryptog.-FI. Deutschland 1, Abt. 4: 310 (1892). Stamm Phykomycophyta Pascher in Beih. bot. Centralbl. 48, Abt. 2: 330 (1931), in part. Biflagellatae Sparrow Aquatic Phycomycetes 487 (1943). Organisms of fungal or chytrid body type, that is, non-pigmented saprophytes or parasites whose bodies are walled filaments or cells with or without rhizoids; the walls consisting partially of cellulose; reproducing asexually by zoospores with paired unlike flagella which are, so far as is known, respectively pantoneme and acroneme, and usually sexually by fertilization, the eggs being distinct cells within the oogonia. The regularly cited example and evident standard genus of the group is Saprolegnia. Conventional botanical classification recognizes within the group of Fungi a sub- ordinate group named Phycomycetes, which is in turn divided into Oomycetes and Zygomycetes, the former including the chytrids. This arrangement suggests an evo- lutionary series, originating perhaps among non-pigmented flagellates, and leading through chytrids, typical Oomycetes, and Zygomycetes to the typical fungi. It does not now appear tenable. Couch (1939) pointed out differences between Oomycetes and Zygomycetes which make any direct connection between them appear quite improbable; and his observations on flagella showed that only a small minority among organisms of chytrid body type have anything to do with the proper Oomycetes. There is an old hypothesis (Sachs, 1874) that Vauchcria may represent the direct ancestry of Saprolegnia. This hypothesis could not be taken seriously while Sapro- legnia and its allies were known to produce heterokont zoospores, while Vaucheria was supposed to be a typical isokont green alga. Now it again appears probable. It implies that in the present group the fungal body type is more primitive than the chytrid. The Oomycetes may be organized as three orders. l.Of fungal body type, i.e., consisting of fila- ments. 2. Essentially aquatic Order 1. Saprolegnina. 2. Mostly not aquatic, parasitic on higher plants Order 2. Peronosporina. 1. Of chytrid body type, i.e., the cells not elong- ated to filamentous form, though sometimes proliferating or producing rhizoids Order 3. LAGENroiALEA. Phylum Phaeophyta [ 77 Order 1. Saprolegnina [Saprolengninae] Fischer in Rabenhorst Kryptog.-Fl. Deutschlandl,Abt.4: 311 (1892). Order Eremospermeae and suborder Mycophyceae Kiitzing Phyc. Gen. 146 (1843), in part. Order Oosporeae Cohn in Hedwigia 11: 18 (1872), in part. Order Oomycetes and suborder Saprolegniineae Engler Syllab. 24 (1892). Order Saprolegniineae Campbell Univ. Textb. Bot. 153 (1902). Order Siphonomycetae Bessey in Univ. Nebraska Studies 7: 286 (1907). Order Saprolegniales Auctt. Order L^p^omzfa/^?^- Kanouse in American Jour. Bot. 14: 295 (1927). Aquatic Oomycetes, filamentous, saprophytic or facultatively parasitic, the zoo- spores diplanetic (exhibiting two periods of swimming) or giving evidence of an ancestral diplanetic condition. The old ordinal names Eremospermeae and Oosporeae designated miscellaneous collections of groups in which this one was listed at or near the beginning. Either one, if taken up, would be applied here, but it seems better to treat them as nomina confusa. 1. Filaments not constricted Family 1. Saprolegniea. 1. Filaments constricted at intervals. 2. Filaments not differentiated into basal and reproductive parts Family 2. Leptomitea. 2. Filaments differentiated into basal and reproductive parts Family 3. Rhipidiacea. Family 1. Saprolegniea [Saprolegnieae] Kiitzing Phyc. Gen. 157 (1843). Family Saprolegniaceae Cohn in Hedwigia 11 : 18 (1872). Aquatic Oomycetes consisting of branching filaments of essentially uniform diameter without crosswalls other than those which set apart differentiated reproductive structures. These well-known organisms are called water molds. According to Coker (1923) there are about eighty definitely recognizable species. They may be parasitic on fishes or saprophytic on organic remains in water or soil. In almost any body of soil or of fresh water they may be found by "baiting," in former practice with dead flies, currently with hemp seeds. Mitosis has rarely "been observed in the vegetative filaments, the nuclei being very minute. Eggs are produced in large globular multinucleate oogonia borne at the ends of filaments. The nuclei in the developing oogonia become enlarged and undergo a single flare of concurrent mitoses (Davis, 1903; Couch, 1932). The sharp-pointed spindles, ending in centrosomes, are formed within the nuclear membrane. The membrane disappears toward the end of the mitotic process, and a nucleolus, which has persisted to this stage, undergoes solution in the cytoplasm. The chromosome numbers (Ziegler, 1953) are 3, 4, 5, 6, or 7. Within each oogonium there appear one or a few minute bodies called coenocentra. One nucleus becomes associated with each coenocentrum; all others break down and disappear. Each surviving nucleus with the cytoplasm associated with it becomes organized as an egg. When several eggs are produced, they share all of the cytoplasm of the oogonium; when only one egg is produced, some of the cytoplasm is left out- side of it. Sperms are produced in small multinucleate antheridia borne at the tips of fila- ments in contact with oogonia. Typically, each individual bears both oogonia and antheridia. Some species are capable of self-fertilization; others exist as two kinds of individuals, each capable of fertilizing the other; some occur as distinct male and 78] The Classification of Lower Organisms ,^t*SJi ' •ITi''!' nVgi 'Villi Fig. 14. — Oomycetes: a. Filaments and sporangia of Dictyuchus sp. x 50. b, C, Zoospores of the second stage of swimming, of Achlya caroliniana and Sapro- legnia ferax, after Couch (1941) x 1,000. d^ Oogonia and antheridia of Dictyuchus X 400. e, f, g, Saprolegnia mixta after Davis (1903) : e, developing oogonium with numerous nuclei x 500; f, metaphase of nuclear division x 2,000; g, developing oogonium in which most of the nuclei have undergone degeneration; a few have become associated with coenocentra, and the cytoplasm is undergoing cleavage to produce eggs about these. Phylum Phaeophyta [ 79 female individuals. Parthenogenesis (reproduction by eggs which have not been fertilized) is rather common in this group. There are no swimming sperms: nuclei from the antheridia reach the eggs through fertilization tubes, or by migration through the periplasm. Ziegler found that the first nuclear divisions of the nucleus of the zygote are meiotic: all cells except the zygotes are haploid. The organs of asexual reproduction are cylindrical sporangia terminal on the fila- ments. Within these the multinucleate protoplasts undergo cleavage into minute uninucleate spores. It is chiefly by details of the behavior of the sporangia and spores (the latter diplanetic, monoplanetic, or not swimming at all) that the dozen genera are distinguished. Diplanetism is the character of zoospores which are not directly infective; they undergo encystment, and the cysts release infective zoospores. During the first stage of swimming, the spores are pear-shaped, with the nucleus drawn out into a beak toward the narrow anterior end, where the flagella are attached. Spores re- leased from cysts for a second period of swimming are bean-shaped, with the flagella attached laterally, each connected through a separate rhizoplast to the nucleus, which lies at some distance from the cell membrane (Cotner, 1930). No explanation of this behavior, whether by phylogeny, genetics, physiology, or competitive advantage, is known. The apparent trend of evolution is to eliminate it. Monoplanetic spores in the present group are usually released from the sporangia as naked protoplasts which undergo encystment and emerge subsequently as flagellate spores of the second form. Saprolegnia releases diplanetic spores through circular pores in the tips of sporangia in which the spores are formed in several rows; new sporangia develop within empty old ones. Organisms which differ from Saprolegnia only in producing new sporangia beside, instead of within, the old ones, were formerly assigned to Achlya, but are now called Isoachlya. Leptolegnia differs from Saprolegnia and Isoachlya in forming spores in a single row. In Achlya proper, the spores are discharged without flagella, to encyst and swim only once. In Thraustotheca the monoplanetic spores are re- leased by irregular breakdown of the distal part of the sporangium. In Dictyuchus the spores become encysted before discharge; their protoplasts escape in the form of secondary swarmers through individual pores in the wall of the sporangium. Salvin (1942) found that cultures while growing release into the medium substances which affect the type of sporangium produced, so that a given culture may be while young of the character of Achlya, and later of the character of Thraustotheca or Dictyuchus. Family 2. Leptomitea [Leptomiteae] Kiitzing Phyc. Gen. 150 (1843). Family Leptomitaceae Schroter in Engler and Prantl Nat. Pflanzenfam. I Tail, Abt. 1 : 101 (1893). Oomycetes consisting of filaments which are constricted at intervals, but are not differentiated into a basal cell and reproductive branches. In sewage or on organic matter decaying in water. Leptomitus, Apodachlya, Apodachlyella, with some seven known species. The numbers of species and degree of distinction of this family and the following do not appear to justify the proposed establishment of a separate order for them. Family 3. Rhipidiacea [Rhipidiaceae] Sparrow in Mycologia 34: 116 (1942). Saprophytes resembling the Leptomitea, the body differentiated into a main part, the basal cell, rhizoids of limited growth, and slender branches bearing the reproductive structures. Sapromyces, Araiospora, Rhipidium, Mindeniella, with perhaps a dozen known species. 80 ] The Classification of Lower Organisms Order 2. Peronosporina [Peronosporinae] Fischer in Rabenhorst Kryptog.-Fl. Deutschlandl,Abt.4: 383 (1892). Suborder Peronosporineae Engler in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. 1: iv (1897). Order Peronosporineae Campbell Univ. Textb. Bot. 155 (1902). Order Peronosporales Auctt. Mostly parasites on terrestrial plants, but including also aquatic parasites and a few saprophytes, the bodies filamentous, reproducing sexually by fertilization, the eggs solitary in the oogonia, reproducing asexually chiefly by conidia, that is, by air- born cells cut off from the ends of the filaments. The conidia are homologous with the sporangia of the Saprolegnina : they germinate in most examples by release of zoospores (which show no signs of diplanetism), but in the more highly evolved examples they give rise to filaments. Ferris (1954) found the zoospores of Phytoph- thora to bear the paired flagella, respectively pantoneme and acroneme, which are typical of Phaeophyta. In the multinucleate oogonia of most members of the group, single flares of mitoses occur. The sharp-pointed spindles, described in some accounts as ending in centro- somes, are formed within the persistent nuclear membrane, which undergoes con- striction during the final stages of mitosis. A coenocentrum appears (this structure was first described as occurring in Albugo, by Stevens, 1899); in general, one nucleus becomes associated with it, and is thus selected as the egg nucleus, the remaining nuclei being cast out to undergo disolution in a body of periplasm. The antheridium develops in contact with the oogonium, and fertilization is accomplished by the growth of a fertilization tube through the periplasm to the egg (Davis, 1900; Stevens, 1899,1901,1902). In Albugo Bliti and A. Tragopogonis, Stevens observed two flares of simultaneous mitoses in the oogonium and antheridium. If this phenomenon were general in the group one would confidently identify it as meiosis. The single coenocentrum attracts many nuclei; the fertilization tube delivers a large number of sperm nuclei; thus multiple karyogamy occurs within a single cell. The further history of the resulting peculiar zygote, containing many nuclei which are not by any evident necessity genetically uniform, is unknown. This order is evidently a specialized offshoot of the preceding. The family Pythiacea is a good example of a transition group; many authorities have assigned it to the pre- ceding order. 1. Producing solitary globular sporangia or conidia at the ends of scarcely specialized filaments; mostly aquatic Family 1. Pythiacea. 1. Producing conidia usually in clusters at the ends of specialized filaments (conidio- phores) ; parasites on land plants. 2. Conidiophores brief, unbranched, the conidia in chains Family 2. Albuginacea. 2. Conidiophores elongate, usually branch- ed, the conidia solitary or clustered, not in chains Family 3. Peronosporacea. Family 1. Pythiacea [Pythiaccae] Schroter in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. 1: 104 (1893). Aquatic parasites and saprophytes releasing zoospores from globular reproductive structures terminal on the filaments, together with para- Phylum Phaeophyta [81 sites attacking land plants under moist conditions. The reproductive structures act as sporangia if formed in water, as conidia if formed in air. Pythium, saprophytic on plant remains in water or parasitic on algae or higher plants, includes some forty species (Matthews, 1931). The few other genera include perhaps a dozen species. Zoophagus produces specialized branches which serve as traps for rotifers which are parasitized and killed. Family 2. Albuginacea [Albuginaceae] Schroter op. cit. 110. Parasites of higher plants, called white rusts, the masses of conidia which push up and burst through the epidetmis being of a white color. Albugo. Family 3. Peronosporacea [Peronosporaceae] Cohn in Hedwigia 11: 18 (1872). Parasites of higher plants, called downy mildews. The ovoid conidia are produced solitary or in clusters, not in chains, on elongate conidiophores, usually branched, projecting through the stomata of the hosts. This numerous group includes the agents of some of the most important diseases of cultivated plants. Plasmopara viti- cola, causing downy mildew of grapes. Phytophthora injestans, the cause of the blight of potatoes which produced the Irish famine of 1846. Peronospora, the many species attacking many kinds of plants. Order 3. Lagenidialea [Lagenidiales] Karling in American Jour. Bot. 26: 518 (1939). Suborder Ancylistineae Engler in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. 1 : iv ( 1897), for the most part, not as to the type genus Ancylistes. Order Ancylistales Auctt., in part. Oomycetes of chytrid body type, parasites consisting of walled cells which are more or less isodiametric, sometimes proliferating or producing rhizoids, but not forming extensive branched filaments. The cells become multinucleate. Mitotic figures of Olpidiopsis as described by Barrett (1912) and McLarty (1941) are quite as in the preceding orders, with sharp-pointed intranuclear spindles apparently with centrosomes at the poles. In the usual course of events, each cell develops an exit tube to the exterior of the host, and the protoplast becomes divided into uninucleate cells which escape as unequally biflagellate zoospores. Fertilization, by the migration of the protoplast of one cell into another, has been observed; the zygote becomes a thick-walled resting spore. 1. Internal parasites without rhizoids. 2. The cells not proliferating. 3. The zoospores diplanetic Family 1. Ectrogellacea. 3. The zoospores not diplanetic Family 2. Olpidiopsidacea. 2. The cells proliferating. 3. Marine Family 3. Sirolpidiacea. 3. Fresh-water Family 4. Lagenidiacea. 1. External parasites with rhizoids Family 5. Thrau stock ytriacea. Family 1. Ectrogellacea [Ectrogellaceae] Scherffel in Arch. Prot. 52: 6 (1925). Ectrogella, Eurychasma, Eurychasmidium, Aphanomycopsis, with about a dozen known species, attacking diatoms and red and brown algae. Family 2. Olpidiopsidacea [Olpidiopsidaceae] Sparrow in Mycologia 34: 116 (1942). Olpidiopsis and a few other genera, with some thirty known species, attack- ing water molds, green algae, red algae, and other aquatic organisms. Family 3. Sirolpidiacea [Sirolpidiaceae] Sparrow 1. c. Sirolpidium and Pontisma, each with one species, attacking marine algae, respectively green and red. 82 ] The Classification of Lower Organisms Family 4. Lagenidiacea [Lagenidiaceae] Schroter in Engler and Prantl Nat. Pfianzenfam. I Teil, Abt. 1 : 89 (1893). Lagenidium, Myzocytium, and Lagenocystis^, with some twenty known species, attacking green algae, rotifers, pollen which has fallen into water, and the roots of grasses. Family 5. Thraustochytriacea [Thraustochytriaceae] Sparrow op. cit. 115. The single species Thraustochytrium proliferum Sparrow was found as solitary cells ex- ternal on certain marine green algae and red algae which are penetrated by means of branching rhizoids. Reproduction is by release of naked protoplasts which become laterally biflagellate after a period of rest. Class 4. MELANOPHYCEA (Ruprecht) Rabenhorst Order Fucacees Lamouroux in Ann. Mus. Hist. Nat. Paris 20: 28 (1813). FucoiDEAE C. Agardh Synops. Alg. Scand. ix (1817). Order Fucoideae C. Agardh Syst. Alg. xxxv (1824). Division (of order Algae) Melanospermeae Harvey in Mackay Fl. Hibern. 157 (1836). Series (of order Algae) Melanospermeae Harvey Man. British Alg. 1 (1841). Order Pycnospermeae and tribe Angiospermeae Kiitzing Phyc. Gen. 333, 349 (1843). Class Fucoideae J. Agardh Sp. Alg. 1 : 1 (1848). Melanophyceae Ruprecht in Middendorff Sibir. Reise 1, part 2: 200 (1851). Class Melanophyceae Rabenhorst Kryptog.-Fl. Sachsen 1: 275 (1863). Stamm Fucoideae Haeckel Gen. Morph. 2: xxxv (1866). Series {Reihe) Phaeophyceae Hauck in Rabenhorst Kryptog.-Fl. Deutschland 2: 282 (1885). Class Phaeophyceae Engler and Prantl Nat. Pfianzenfam. H Teil: 1 (1889), Class Dictyotales Engler in Engler and Prantl Nat. Pfianzenfam. I Teil, Abt. 2 : ix(1897). Classes Phaeosporeae, Tetrasporeae, and Cyclosporeae Bessey in Univ. Nebraska Studies 7: 288, 290 (1907). CXdiSS Dictyoteae Schaffner in Ohio Naturalist 9: 448 (1909). Subclass Melanophyceae Setchell and Gardner in Univ. California Publ. Bot. 8: 387 (1925). Classes Isogeneratae, Heterogeneratae (with subclasses Haplostichinae and Poly- stichinae) and Cyclosporeae Kylin in Kungl. Fysiog. Sallsk. Handl. n. f. 44, no. 7: 91 (1933). Filamentous or thallosc Phaeophyta, yellow to brown in color and living by photo- synthesis, producing reproductive cells with paired unequal flagella. These are the typical brown algae. They are almost exclusively marine, being abundant along with red and green algae on most coasts, and particularly abundant farther toward the poles than the red and green groups. The lower brown algae are branched filaments of microscopic dimensions, commonly epiphytic on other algae. More highly developed examples are thallosc and anchored to rocks. Some of these, particularly the ones whose English name is kelp, reach great sizes and considerable elaboration of structure. Papenfuss (in Smith, 1951) gives the number of genera as about 240, and that of known species as about fifteen hundred. ^Lagenocystis nom. nov. Lagena Vanterpool and Ledingham in Canadian Jour Res. 2: 192 (1930), non Parker and Jones 1859. L. radicicola (Vanter- pool and Ledingham) comb. nov. Phylum Phaeophyta [ 83 The cells are walled chiefly with readily hydrolyzable modified polysaccharides. Algin, the soda extract of kelps, consists of chains of oxidized mannose units. A poly- saccharide of the sugar fucose, with a sulfate radicle to each sugar unit, is also present. A small percentage of cellulose is present, apparently as the immediate investment of each protoplast. A glycogen- or dextrin-like dextrosan, laminarin, is stored (Miwa, 1940; Tseng, 1945). The plastids contain chlorophylls a and c (Strain, in Franck and Loomis, 1949) and carotin; xanthophyll is also present in the more primitive examples. In all examples, there is an additional carotinoid called fucoxanthin, which produces the brown color. The analytic process of separating the pigments yields also a sterol, fucosterol, not found in green plants; but this substance, and fucoxanthin, are found in chrysomonads, green Heterokonta, and diatoms (Carter, Heilbron, and Lythgoe, 1939). Cytological study of a considerable variety of brown algae (Swingle, 1897; Farmer and Williams, 1896; Mottier, 1898, 1900; Simons, 1906; Yamanouchi, 1909, 1912; McKay, 1933) has shown that the spindle and chromosomes appear within an intact nuclear membrane which disappears during the later stages of division. A centrosome, usually with radiating rays, is present outside of the membrane at each pole of the spindle. In Stypocaulon, a comparatively primitive brown alga, Swingle found the centrosome to be a permanent structure, dividing as a preliminary to each division of the nucleus. In the generality of brown algae, the centrosomes appear de novo as division begins. Swimming cells are produced by primitive brown algae as spores and as morpholo- gically undifferentiated gametes; in the most advanced brown algae, such cells are produced only as sperms. The flagella are attached laterally. The anterior flagellum is the longer except in order Fucoidea (Kylin, 1916). Longest (1946) found in Ectocarpus that the anterior flagellum is pantoneme, and the posterior one acroneme. The swimming cells are without walls, and contain, beside the nucleus, usually one plastid and a light-sentitive speck, the stigma or eyespot. They are quite small. No system of structures linking the nuclei, centrosomes, and flagella has been discovered. Thuret (1850) discovered that most brown algae produce swimming cells from structures of two different sorts, which he named (1855) respectively plurilocular sporangia and unilocular sporangia. The difference between them is this. In the developing plurilocular structure, each division of the nucleus is followed by division of the protoplast and deposition of a wall, with the result that the swimming cells emerge from separate walled spaces. In the unilocular structure, the nucleus divides repeatedly before the protoplast divides; the protoplast then undergoes cleavage to produce swimming cells which emerge from a single walled space. A number of studies (Clint. 1927; Higgins, 1931; Knight, 1923, 1929) have shown that the first two nuclear divisions in the unilocular structure are normally meiotic. Unilocular structures occur normally only on diploid individuals and release haploid swimming cells. A few exceptional species, however, are known to bear unilocular structures which produce swimming cells without the intervention of meiosis. In Ectocarpus siliculosus as studied by Berthold (1881) at Naples, the swimming cells from unilocular structures are spores which give rise to haploid individuals. In the same species as studied in the Irish Sea by Knight (1929), they were found to act as gametes, conjugating and giving rise to diploid individuals. Diploid and hap- loid individuals of Ectocarpus are alike, and E. siliculosus may be said to have a facultatively complete homologous life cycle. The haploid individuals produce pluri- locular reproductive structures; the swarmers from these act either as spores, re- 84] The Classification of Lower Organisms Fig. 15. — Stages of nuclear division in Stypocaulon x 1,000 after Swingle (1897). Phylum Phaeophyta [ 85 producing the haploid stage, or as gametes, initiating the diploid stage. The diploid individuals produce both plurilocular and unilocular reproductive structures. The swarmers from the former are spores, reproducing the diploid body. The swarmers from the latter act either as spores, giving rise to haploid individuals, or as gametes, reproducing the diploid body. It is believed that the brown algae arose by evolution from order Ochromonadalea. Filamentous organisms with a facultatively complete homolgous life cycle, as just described, are believed to be primitive among them : such organisms appear to be the starting point of evolution in many features. The filaments have become differentiated and woven into thalli, and thalli of tridimensionally placed cells have been produced. The haploid and diploid stages have become differentiated. The plurilocular and unilocular structures have undergone specialization. Even in the most primitive brown algae, there is a physiological differentiation of gametes; this has evolved into extreme morphological differentiation. Every one of these evolutionary changes ap- pears to have occurred in more than one line of descent; research is constantly reveal- ing intermediate examples and rather free parallel evolution. Conservative classification, such as that of Fritsch (1945), recognizes as orders a comparatively primitive miscellany followed by a series of small derived groups marked by distinctive specializations. Features of the life cycle, as applied to classi- fication by Taylor (1922), Oltmanns (1922), Svedelius (1929) and Kylin (1933), are not reliable as marks of natural groups. Kylin provided three classes (one of them divided into two subclasses) and twelve orders. His system appears to provide an excessive number of subdivisions of high category within a moderately small group exhibiting no very profound evolutionary gaps. Tentatively, the seven orders dis- tinguished as follows may be recognized. 1. Producing spores, that is, cells which germi- nate without syngamy. 2. All spores bearing flagella. 3. Having an alternation of haploid and diploid stages which are alike, both being filamentous; or else com- pletely lacking one of these stages. 4. The filaments uniseriate Order 1. Phaeozoosporea. 4. The filaments becoming pluri- seriate Order 2. Sphacelarialea. 3. Not as above. 4. Haploid stage thallose, not dis- tinctly less highly developed than the diploid stage Order 5. Cutlerialea. 4. Haploid stage filamentous, dis- tinctly less highly developed than the diploid stage. 5. Diploid stage filamentous; or, if partially or com- pletely thallose, the thal- lose part with apical growth Order 4. SpoROCHNoroEA. 5. Diploid stage thallose, its growth intercalary Order 6. Laminariea. 2. Producing large non-motile spores Order 3. Dictyotea. 86 ] The Classification of Lower Organisms 1. Producing no spores; all individuals diploid and reproducing exclusively sexually Order 7. FucoroEA. Order 1. Phaeozoosporea [Phaeozoosporeae] Hauck in Rabenhorst Kryptog.-Fl. Deutschland 2: 312 (1885). Order Syntamiidae Areschoug in Act. Reg. Soc. Upsala 14: 387 ( 1850) , in part; a nomen confusum. Order Ectocarpeae J. Agardh Sp. Alg. 1: 6 (1848), preoccupied by family EcTOCARPEAE KUtzing (1843). Section (of Algae Zoosporeac) Phaeosporeae Thuret in Ann. Sci. Nat. Bot. ser. 3, 14: 233 (1850). Order Phaeosporeae Wettstein Handb. syst. Bot. 1: 173 (1901). Order Ectocarpales Bessey in Univ. Nebraska Studies 7: 288 (1907). Order Phaeosporales and suborder Ectocarpineae Taylor in Bot Gaz. 74: 435, 436 (1922). Microscopic brown algae of the form of undifferentiated uniseriate branching fila- ments, mostly with distinct haploid and diploid stages (exceptionally lacking the former), the stages distinguishable only by the limitation of unilocular reproductive structures to the diploid stage, the gametes morphologically uniform. The order is typified by Ectocarpus, which is by coincidence also the theoretical ancestral type of the brown algae, the living organism which supposedly represents the evolutionary origin of the group. Recent systems of classification limit this order, formerly construed as extensive, to this genus and a few others, as Pylaiella and Streb- lonema, which make up the family Ectocarpea [Ectocarpeae] Kiitzing (family Ecto- carpaceae Cohn). Order 2. Sphacelarialea [Sphacelariales] (Oltmanns) Engler and Gilg Syllab. ed. 9 u. 10: 27 (1924). Order Sphacelarieae J. Agardh Sp. Alg. 1: 27 (1848), preoccupied by family Sphagelarieae Kiitzing (1843). Sphacelariales Oltmanns Morph. u. Biol. Alg. ed. 2, 2: 2 (1922). Brown algae distinguished from the Ectocarpea only by features of the vegetative structure, namely that the filaments have large apical cells, and that the cells cut off from them divide lengthwise without increasing considerably in thickness, with the result that the filaments consist of tiers of cells. The life cycle is the same as in Ecto- carpea. Family Sphacelariea [Sphacelarieae] Kiitzing (family Sphacelariaceae Cohn) includes Sphacelaria and Stypocaulon. A few other families have been segregated. Order 3. Dictyotea [Dictyoteae] Greville Alg. Brit. 46 (1830). Tribe Dictyoteae Harvey in Mackay Fl. Hibern. 159 (1836). Family Dictyoteae Kiitzing Phyc. Gen. 337 (1843). Order Dictyotaceae Hauck in Rabenhorst Kryptog.-Fl. Deutschland 2: 302 (1885). Class Dictyotales Engler in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. 2 : ix (1897). Akinetosporeae Oltmanns Morph u. Biol. Alg. 1: 473 (1904). Order Tilopteridales and Class Tetrasporeae with order Dictyotales Bessey in Univ. Nebraska Studies 7: 290 (1907). Scries Aplanosporeae Setchell and Gardner in Univ. California Publ. Bot. 8: 649 (1925). Phylum Phaeophyta [ 87 Filamentous or thallose brown algae with haploid and diploid stages equally de- veloped, producing large spores without flagella, solitary or few in the sporangia. Here are placed two families, Tilopteridea and Dictyotacea. Family Tilopteridea [Tilopterideae] Cohn is a small group, apparently known only from European coasts. They are evidently closely related to the Ectocarpea. They consist of branching filaments which may become pluriseriate. In Haplospora (poorly known; but Tilopteris and other genera are even more so), the haploid stage bears both plurilocular structures, releasing minute swimming cells of the structure usual in brown algae, and unilocular structures which release their contents as single uninucleate protoplasts without flagella. The diploid stage bears only unilocular structures which release their contents as single quadrinucleate non-motile spores. It is inferred that the swimming cells from the plurilocular structures are sperms, and that the protoplasts released from the unilocular structures on haploid bodies are eggs, capable, however, of reproducing the haploid stage if not fertilized; further, that the nuclei of the quadrinucleate spores released by diploid individuals are hap- loid, and become on germination the nuclei of as many cells of the haploid body. The Tilopteridea are believed to represent the evolutionary transition between Ectocarpea and the following family. Family Dictyotacea [Dictyotaceae] (Hauck) Kjellmann includes about twenty genera, Dictyota, Zonaria, Padina, etc., with about one hundred species which are commonest on the coasts of warmer oceans. They are thalli of moderate size, erect and dichotomously branched or appressed and fan-shaped. They grow by the division of a single apical cell or a row of apical cells in each branch. The cells multiplying behind the apical cells become differentiated into two tissues, superficial small cells rich in plastids and internal larger ones with fewer plastids, forming in different species single or multiple layers of cells. The Hfe cycle has been studied by Mottier (1898, 1900), Williams (1898), and Haupt (1932). There are distinct male haploid individuals, female haploid indivi- duals, and diploid individuals, all of the same vegetative structure. The males pro- duce sperms from clusters of densely packed plurilocular antheridia. The females produce eggs solitary in large oogonia solitary or clustered on the thalli. The eggs are without flagella. The diploid individuals produce unilocular sporangia of much the same structure as the oogonia. In Zonaria, each sporangium produces eight non- motile spores; in Dictyota, each one produces four. Order 4. Sporochnoidea [Sporochnoideae] Greville Alg. Brit. 36 (1830). Order Chordarieae Greville op. cit. 44. Order Chordariaceae Haeckel Gen. Morph. 2: xxxv (1866). Orders Desmarestiales and Chordariales Setchell and Gardner in Univ. Califor- nia Publ. Bot. 8: 554, 570 (1925). Order Sporochnales Sauvageau in Compt. Rend. 182: 364 (1926). Brown algae producing motile spores, the haploid stage reduced to scant undiffer- entiated filaments, the diploid stage filamentous or thallose, when thallose with apical growth. Ralfsia is an exception to the formal characters of the order: it has a haploid stage of the same structure as the diploid. This is a rather miscellaneous assemblage, rather arbitrarily separated from Phaeozoosporea on the one hand and from Lamin- ariea on the other. The haploid body of the form of a short-lived body of a few undifferentiated fila- ments, like a reduced Ectocarpus, bearing gametangia reduced to single cells, has 88 ] The Classification of Lower Organisms been demonstrated by Kylin ( 1933, 1934, 1937) in a wide variety ot genera, as Asco- cyclus, Desmotrichum, Mesogloia, Eudesme, Leathesia, and Stilophora. In the more primitive examples, the gametes are not visibly differentiated; in more advanced ones, as Carpomitra and Desmarestia, different haploid bodies produce respectively smaller sperms and larger eggs, the latter non-motile. There is a series of families, Ralfsiacea, Myrionematacea, Myriogloiacea, Meso- gloiacea, and others, in which the diploid body consists of filaments differentiated into different types. In the simplest of these, the germinating zygote produces in the first place a minute thallus-like plate, generally epiphytic on other algae, one cell thick, and consisting obviously of branched filaments of limited growth. From this plate grow erect filaments. Some of these are simply cylindrical and appear nutritive in function; others are attenuate, and may function in protection or in absorbing materials from the water; yet others bear the reproductive structures, unilocular or plurilocular or both. In the more advanced families, the diploid body, after passing through a Ralfsia- or Myrionema-Vike stage, may produce a compacted column of filaments with a terminal plate of apical cells. Besides adding cells to the column, the apical plate gives rise to a fascicle of attenuate hairs projecting forward. Members of the families Chordariacea, Sporochnea, and Desmarestiacea produce cylindrical or flattened thallose bodies of tridimensionally placed cells differentiated into an outer layer of small actively photosynthetic cells and an inner mass of nearly colorless cells. Super- ficial hairs, growing in intercalary fashion, may become few, and growth may become restricted to a single apical cell. By differences in the detailed manner of growth, Setchell and Gardner distin- guished two orders among the thalloid forms just mentioned. It is evident, however, that the thallose structure (and, likewise, differentiation of gametes) has developed repeatedly and independently in the present group. Knowledge which would make it possible to divide it into several recognizably natural orders is not yet available. Order 5. Cutlerialea [Cutlcriales] Bessey in Univ. Nebraska Studies 7: 289 ( 1907). Brown algae producing motile spores, the haploid and diploid bodies being macro- scopically visible thalli, alike or different. This is a small group, of one family, Cutleriacea, with two genera, Zanardinia and Cutlcria, known chiefly from the Mediterranean. In Zanardinia, both haploid and diploid bodies are erect and rather freely branched. In Cutlcria, the haploid bodies are of this description, while the diploid bodies are appressed and fan-shaped. The distinct diploid bodies of Cutlcria were originally named as a different genus, Aglaozonia. Falkenberg (1879) first showed that Cutlcria and Aglaozonia arc stages of the same thing; Yamanouchi showed that they are respectively a haploid stage with 24 chromosomes and a diploid stage with 48. The growing margins of the thalli consist of laterally compacted filaments grow- ing by the divisions of a band of mcristematic cells which produce free hairs in the distal direction and a continuous body of cells in the proximal direction. The latter cells are capable of further division, and produce a body several cells thick, with small cells rich in plastids on the surface and larger ones with fewer plastids in the interior. Haploid individuals bear clusters of stalked plurilocular structures of two types, almost always on different individuals, the larger ones consisting of fewer cells which release eggs, the smaller of more numerous cells which release sperms. Both kinds of Phylum Phaeophyta [ 89 gametes are flagellum-bearing cells of the type usual in brown algae. The eggs are capable of germination without fertilization, reproducing the haploid stage. Diploid individuals bear clusters of unilocular sporangia. It is only in the life cycle that the Cutlerialea are decidedly different from higher Sporochnoidea such as Desmarestia. Their evolutionary origin is explicable by the hypothesis of a single mutation which enabled the haploid stage to exhibit the com- paratively complicated morphology of the diploid stage, instead of being rudimentary as in all Sporochnoidea except Ralfsia (and the exceptional life cycle of Ralfsia would be explained by a similar mutation in some primitive example of Sporochnoi- dea, such as Myrionema) . Older 6. Laminariea [Laminarieae] Greville Alg. Brit. 24 (1830). Order Pycnospermeae Kiitzing Phyc. Gen. 333 (1843). Order Laminariaceae Haeckel Gen. Morph. 2: xxxv (1866). Laminariales Oltmanns Morph. u. Biol. Alg. ed. 2, 2: 2 (1922). Order Laminariales Engler and Gilg Syllab. ed. 9 u. 10: 27 ( 1924). Order Dictyosiphonales Setchell and Gardner in Univ. California Publ. Bot. 8: 586 (1925). Order Punctariales Kylin in Kungl. Fysiog, Sallsk. Hand!, n. f. 44, no. 7 : 93 (1933). Brown algae with motile spores, the haploid stages reduced to microscopic dimen- sions, the diploid stages thallose, growing in intercalary fashion. This numerous group, like the preceding small one, is evidently a specialized off- shoot from order Sporochnoidea. The familiar examples are the kelps, whose large diploid bodies are differentiated into definite members. Kylin considered his order Punctariales to represent the transition to the kelps. They are thallose, without dif- ferentiation of members, but their microscopic and reproductive characters, as ob- served in Soranthera by Angst (1926, 1927), tend to confirm Kylin's opinion, and they are accordingly included in the same order with the kelps. Papenfuss (1947) pointed it out that the Punctariales of Kylin are essentially the same group as the Dictyosiphonales of Setchell and Gardner. Sauvageau (1915) first showed that the reproduction of kelps is sexual. The grossly visible individuals produce zoospores; these, on germination, produce micro- scopic filamentous haploid individuals, generally of distinct sexes, releasing gametes from unicellular gametangia. The eggs are without flagella, and it is characteristic of them that in emerging from the oogonia they become attached at the opening (Kylin, 1916, 1933; Myers, 1928; McKay, 1933; Kanda, 1936; Hollenberg, 1939). The same things are true in Soranthera, except that the eggs, although much larger than the sperms, are also flagellate. The visible bodies of kelps consist of three kinds of members, holdfasts (hapteres), being stout root-like growths by which the individuals are anchored to rocks, and stalks and blades comparable to stems and leaves. Growth is most active at the sum- mits of the stalks. The histology is the same in all members (A. I. Smith, 1939). There is a superficial photosynthetic tissue of small cells rich in plastids; on the hold- fasts and stalks, this tissue is meristematic, adding cells to the tissue within and in- creasing the thickness. Internally there is a cortex of larger cells with fewer plastids. In the center there is a medulla containing trumpet fibers, filaments whose cells are expanded where they meet and marked by pit-pairs. In the trumpet fibers of Nereo- cystis there are actual perforations from cell to cell. The trumpet fibers are not quite 90] The Classification of Lower Organisms Fig. 16. — Familiar kelps of Pacific North America: a, Egregia Menziesii; h, Nereo- cystis Luetkeana; c, Macrocystis pyrifera; d, Postelsia palmaeformis. All approxi- mately X /a- Phylum Phaeophyta [91 perfectly analogous to the sieve tubes of higher plants; the nuclei remain alive. The minute zoospores are produced in unilocular sporangia. These occur on the surface of the body in dense masses, intermingled with, and protected while young by, spe- cialized sterile hairs. Individuals of Laminaria consist simply of hapteres, a stalk, and one or more terminal blades. In various other genera, growth occurs in such fashion as to cause the blades to split at the base. With further growth, the splits extend to the margins of the blades and increase their number, while intercalary growth at the transitions between the stalks and the blades produces elongation and branching of the stalks. Early explorers described the stalks of Macrocystis pyrifera as reaching prodigious lengths, matters of hundreds of meters, and these accounts have been repeated in textbooks down to recent times. Frye, Rigg, and Crandall (1915) found a maximum length of somewhat less than fifty meters. The stalks are dichotomously branched to a moderate extent and bear series of blades, each with a pear-shaped pneumato- cyst or float at the base. The stalks of Nereocystis Luetkeana also were said to be extremely long, but the recent observers did not find them to attain fifty meters. They are unbranched and bear a single large float from which spring several blades which may exceed four meters in length. This great organism is an annual, growing and dying within a year. Postelsia palmaeformis, called the sea palm, grows on rocks ex- posed to surf. It has erect stalks some 30 cm. tall bearing many pendant linear blades. Egregia Menziesii has flattened stalks many meters long with fringes of floats and blades along the margins. Laminaria is widely distributed. Macrocystis occurs on the northwest coast of North America and in southern oceans. The other kelps which have bef:n mentioned are confined to the northwest coast of North America. On coasts where they occur, kelps are used as fertilizer. They have been used com- mercially as sources of potash, as much as 1-3% of the fresh weight being K as K2O (Cameron, 1915); they have been used also as sources of iodine. These uses are not economic at most times. Setchell and Gardner divided the proper kelps, of which there are about one hundred species, into four families. The groups of less elaborate structure which ap- pear properly to be placed in the same order are treated by Papenfuss (under Dictyo- siphonales) as six families. Order 7. Fucoidea [Fucoideae] C. Agardh Syst. Alg. xxxv (1824). FucoiDEAE C. Agardh Synops. Alg. Scand. ix (1817). Tribe Angiospermeae Kiitzing Phyc. Gen. 349 (1843). Order Cyclosporeae Areschoug in Act. Roy. Soc. Upsala 13: 248 (1847). Order Fucaceae J. Agardh Sp. Alg. 1 : 180 ( 1848). Order Sargassaceae Haeckel Gen. Morph. 2: xxxv (1866). Order Fucales Bessey in Univ. Nebraska Studies 7: 290 (1907). Order Cyclosporales and suborder Fucineae Taylor in Bot. Gaz. 74: 439 (1922). Class Cyclosporeae Kylin in Kungl. Fysiog. Sallsk. Handl. n. f. 44, no. 7: 91 (1933). Thallose brown algae, producing no spores, diploid in all stages except the gametes; the latter being sperms, whose posterior flagellum is longer than the anterior one, and non-motile eggs. The genus Fucus L. is to be construed as the type genus of order Fucoidea, class Melanophycea, and phylum Phaeophyta. Two families are usually recognized (others have been segregated). In family Fucea [Fuceae] Kiitzing (family Fucaceae Cohn), called the rockweeds, the bodies 92] The Classification of Lower Organisms are flat dichotomously branching thalli. In family Sargassea [Sargasseae] Kiitzing there is a differentiation of holdfasts, stalks, blades, and floats. Growth is by division of a single apical cell in each branch or member. There are the usual two tissues, a superficial photosynthetic tissue of small cells and an inner tissue of larger cells which pull apart to produce a spongy or fibrous mass. The gametangia are borne, mixed with sterile hairs, in pits called conceptacles. These are clustered, in the Fucea near the tips of branches which have ceased to grow (these tips are swollen, and are called receptacles), in the Sargassea on special branches. Rarely, oogonia and antheridia occur in the same conceptacles; not infre- quently, they occur in different conceptacles on the same individuals; commonly, they occur on different individuals. Male and female conceptacles may be distinguished by color, the male being orange-yellow, the female of the same dark color as the thalli. Male conceptacles are full of branching hairs bearing minute antheridia. In each antheridium, the original single nucleus undergoes six successive simultaneous divi- sions, producing sixty-four nuclei. These become the nuclei of sperms. Female con- ceptacles contain fewer, larger, oogonia, in which the nuclei divide three times, pro- FiG. 17. — Microscopic reproductive structures of Laminaria yezoensis after Kanda ( 1938) : a, male haploid individual releasing sperms; b, sperm; C, zoospore; d, female haploid individual of three cells; e, female individual with an egg extnided from the oogonium and attached in the mouth f, female individual with two young diploid individuals attached at the mouths of oogonia. All x 1,000. Phylum Phaeophyta [ 93 ducing eight. In Fucus, these become the nuclei of as many eggs. In other genera, the number of functional eggs is reduced by degeneration of some of them, or of some of the nuclei before cell division. In Sargassum, Kunieda (1928) found each oogon- ium to produce a single egg in which seven nuclei undergo dissolution while one re- mains to function. The first two nuclear divisions in each gametangium are meiotic. Farmer and Williams (1896) and Strasburger (1897) showed that the bodies are diploid; Yama- nouchi (1909) first gave a full account of the meiotic process. The haploid chromo- some number of Fucus vesiculosus is 32. In Sargassum Horneri Kunieda found it to be 16. By a swelling of colloidal material in the conceptacles, the gametangia are forced out into the water, where they burst and release the gametes. Fucus was one of the first organisms in which syngamy was observed. Thuret (1855) saw multitudes of sperms swarm about the eggs, and showed that without sperms the eggs would not develop. This much had already been observed in frogs and certain fishes; the dis- covery that the essential process is the union of just one sperm with the egg was not made until later. The growing zygotes give rise directly to diploid thalli. ■ The gametangia of the Fucoidea appear to be homologous with the unilocular sporangia of other brown algae. In the gametangia, as in unilocular sporangia, the meiotic divisions are followed by a few divisions of the haploid nuclei: the Fucoidea are not quite perfect examples of the reduction of the haplod stage to the gametes only. As to which other brown algae may have provided their evolutionary origin, there is no very satisfactory hypothesis; Sporochnus shows certain resemblances. Chapter VII PHYLUM PYRRHOPHYTA Phylum 3. PYRRHOPHYTA Pascher Order Astoma Siebold in Siebold and Stannius Lehrb. vergl. Anat. 1: 10 (1848). Order Phytozoidea Perty Kennt. kleinst. Lebensf. 161 (1852). Flagellata Cohn in Zeit. wiss. Zool. 4: 275 (1853). Orders Flagellata and Cilio-flagellata Claparede and Lachmann Etudes Infus. 1: 73 (1858). Suborder Mastigophora Diesing in Sitzber. Akad. Wiss. Wein Math. -Nat. CI. 52, Abt. 1: 294 (1866). Stdmme Flagellata and Noctilucae Haeckel Gen. Morph. 2: xxv, xxvi (1866). Class Flagellata Kent Man. Inf. 1: 27, 211 (1880). Class Mastigophora and orders Flagellata, Dinoflagellata, and Cystoflagellata Butschli in Bronn Kl. u. Ord. Thierreichs 1, Abt. 2, Inhalt (1887). Class Peridineae Wettstein Handb. syst. Bot. 1: 71 (1901). Divisions Flagellatae and Dinoflagellatae Engler Syllab. ed. 3: 6, 8 (1903). Pyrrhophyta, Eugleninae, and Chloromonadinae Pascher in Ber. deutschen Bot. Gess. 32: 158 (1914). Stdmme Pyrrhophyta and Euglenophyta, and Abteilungen Cryptophyceae, Des- mokontae, and Dinophyceae, Pascher in Beih. bot. Centralbl. 48, Abt. 2: 325, 326 (1931). Division Pyrrhophyta G. M. Smith Freshw. Algae 10 (1933). Protistes trichocystiferes ou progastreades Chadefaud in Ann. Protistol. 5: 323 (1936). Phyla Pyrrhophycophyta and Euglenophycophyta Papenfuss in Bull. Torrey Bot. Club 73: 218 (1946). Unicellular or colonial organisms, typically with brown or green plastids, flagel- late, the flagella solitary or more than one and unequal, the cells marked by grooves or pits and sometimes containing trichocysts, i. e., minute structures which lie close to the cell membrane and eject thread-like bodies when stimulated. The organisms included here are the ones conventionally treated as four orders of pigmented flagellates, cryptomonads, dinoflagellates, euglenids, and chloromonads. These groups include organisms of the same varied body types, algal, amoeboid, and chytrid, that occur in other groups in which the flagellate body type is construed as typical. Peridinium may be considered to be the type of the phylum. Deflandre (1934) designated as stichoneme [stichonemate) the type of flagcllum which bears a single file of appendages, and which had been discovered by Fischer (1894) in Euglena. Petersen (1929) reobserved the stichoneme flagellum of Etiglena, and found it also in other euglenids, Phacus and Trachelomonas. Deflandre found that one flagellum is stichoneme in various further euglenids (but not in all), and also in the dinoflagcllate Glenodinium. This is the only report of a stichoneme flagel- lum outside of the euglenid group. The fine structure of the flagella of cryptomonads and chloromonads has not been determined. In some cryptomonads, as Chilomonas, the cells contain granules which stain blue with iodine; if these are not starch, one knows not what to call them. Dino- flagellates produce a so-called starch which gives a reddish color with iodine, and many of them have walls of a so-called cellulose which gives a reddish color with Phylum Pyrrhophyta [ 95 zinc chlor-iodide. The euglenids store granules of a white solid believed not to be starch and called paramylum. The plastids of cryptomonads and dinoflagellates are of various colors, oflF-color green, yellow, brown, bluish, or red. Those of dinoflagellates contain chlorophylls a and e; the latter is an exceptional chlorophyll which occurs also in Tribonema. Euglenids and chloromonads are typically of the same bright green color as typical plants, and the euglenids are known to have the same chlorophylls, a and b, as typical plants (Strain, in Franck and Loomis, 1949). The groups here brought together exhibit family resemblances in details of the mitotic process, so far as these are known. The nuclear membrane usually persists through the process. In many examples the chromosomes appear to be present at all times, and are quite numerous, elongate, and of the appearance of strings of beads. In mitosis, quite as one would assume, they divide lengthwise; the point had been disputed, and was established by Hall (1923, 1925, 1937) and Hall and Powell (1928). There is a neuromotor apparatus consisting of a centrosome at or near the nuclear membrane together with one or more rhizoplasts connecting it to as many blepharoplasts at the bases of the flagella. No spindle has been seen, unless the peculiar structure, seen in Noctiluca outside of and next to the dividing nucleus, is such. The centrosomes may lie at the sides of the dividing nucleus instead of at its ends. In the euglenids and some dinoflagellates the nucleus contains a nucleolus-like body which does not disappear during mitosis, but divides as the chromosomes do. There are few reports of sexual processes in this group. Pascher (1914) united the crytomonads and dinoflagellates in a group which he named Pyrrhophyta. He and those who follow him leave the euglenids as an iso- lated group. Tilden (1933) placed the four groups of flagellates with which we are here concerned in division Chrysophyceae, while leaving the Phaeophyceae as a distinct division. Her arrangement does not appear to be contrary to nature: the cryptomonads are apparently not very far removed from the chrysomonads. The different arrangement here maintained, by which the brown algae instead of the cryptomonads and so forth are placed in the same phylum with the chrysomonads, is believed to have the advantage that that phylum as least is well marked by char- acter. Chadefaud (1936) proposed a group consisting of the four groups of flagellates here under consideration together with the Infusoria: this on the ground that the Infusoria also have deeply indented cells containing trichocysts. He did not give to his proposed group a place in the taxonomic system by assigning it to a category and giving it a Latin name: he called it by the French common names protistes trichocystiferes and progastreades. He suggested two ideas: that if a cell marked by a considerable indentation should become divided into many cells forming two layers, respectively superficial and against the indentation, the resulting structure would be a gastrula; and that the gastrula, and, in fact, the kingdom of animals, might have come into existence in this fashion. Perhaps because of novelty, these ideas seem far-fetched. So far as it concerns flagellates, Chadefaud's grouping appears sound and has been followed in giving limits to the present phylum. The phylum is treated as a single class. Class MASTSGOPHORA (Diesing) Bu'tschli Classes Cryptomonadineae , Rhizocryptineae, Cryptocapsineae, Cryptococcineae, Desmomonadineae, Desmocapsineae, Dinoflagellatae, Rhizodininae, Dinocap- 96 ] The Classification of Lower Organisms sineae, Dinococcineae, Dinotrichineae, Euglenineae, and Euglenocapsineae Pascher in Beih. bot. Centralbl. 48, Abt. 2: 325, 326 (1931). Classes Chloromonadina, Euglenoidina, and Cryptomonadina Hollande in Grasse Traite Zool. 1, fasc. 1: 227, 238, 285 (1952). Further synonymy as of the name of the phylum. Characters of the phylum. There are about one thousand known species. Clearly, thirteen classes for their accommodation, as proposed by Pascher, are excessive; perhaps one goes too far in the other direction in making the entire group a single class. The type of the class is the euglenid Astasia. This is true because the family Astasiaea was listed first in the earliest appearance of the traditional group Flagellata or Mastigophora in due taxonomic form, as order Astoma Siebold, If the euglenids are set apart, taking with them the class name Mastigophora, the remaining larger class will be called Peridinea [Peridineae] Wettstein. The traditional four orders are tenably natural; but that of dinoflagellates includes about four-fifths of the species, while the chloromonad group is very inconsiderable. The system will be more convenient if the former order is divided into three, and if the latter is included in the euglenid order. The resulting five orders are distinguished as follows: 1. Pigmentation if present brown, olive, or the like; flagella normally two. 2. Flagella at the anterior end of the cell, not moving in longitudinal and trans- verse grooves. 3. Not walled in the flagellate con- dition, flagella not markedly dif- ferentiated, or not differentiated as anterior and circumferential .Order 1 . Cryptomonadalea. 3. Usually walled in the flagellate condition; flagella respectively an- terior and circumferential Order 2. Adiniferidea. 2. Flagella attached laterally, respectively longitudinal and circumferential, moving in grooves impressed upon the cells. 3. Not walled in the flagellate con- dition Order 3. Cystoflagellata. 3. Flagellate cells with a wall usually of articulated plates Order 4. Cilioflagellata. 1. Pigmentation if present typically bright green, flagella normally solitary, sometimes two or more Order 5. Astoma. Order 1. Cryptomonadalea [Cryptomonadales] Engler Syllab. ed. 3: 7 (1903). Subclass Cryptomonadineae Engler in Engler and Prantl Nat. Pflanzenfam. ITeil, Abt. la: iv (1900). Cryptophyceae, including Phaeocapsales and Cryptococcales, Pascher in Ber. deutschen bot. Gess. 32: 158 (1914). Order Cryptomonadinae Pascher Siisswassei-fl. Deutschland 1: 28 (1914). Order Cryptomonadina Doflein Lehrb. Prot. ed. 4: 417 (1916). Phylum Pyrrhophyta [97 Order Cryptomonadida Calkins Biol. Prot. 265 (1926). Orders Cryptocapsales and Cryptococcales Pascher in Beih. bot. Centralbl 48, Abt. 2: 325 (1931). Solitary (exceptionally colonial) cells, usually with one or two plastids of various colors, usually observed in the motile condition, then naked, of dorsiventral (excep- tionally isobilateral) symmetry, with two anterior flagella which are not markedly differentiated or not respectively anterior and circumferential. The resting nucleus contains a karyosome, i. e., a globule which occupies most of t t>.>. Fig. 18. — a, Cryptomonas sp. b, Rhodomonas baltica after Kylin ( 1935 ) . c, Chi- lomonas Parmecium. d, Cyathomonas sp. e, Sennia sp. f. Vegetative cell, and g, zoospore of Paradinium Pouchetii after Chatton (1920). All x 1,000. its volume and contains most of the chromatin. Dangeard (1910) and Belar (1916) have observed details of mitosis. The numerous chromosomes appear within an intact nuclear membrane and form a disk- or drum-shaped figure with its axis at right angles to the axis of the cell. No granule more massive than the chromosomes persists and divides with them. About thirty species are known. They may be treated as five families. 1. Flagellate cells elongate, with one plane of symmetry. 2. Not parasitic, flagella not markedly dif- ferentiated. 3. Non-motile in the vegetative con- dition Family 1. Cryptococcacea. 3. Flagellate in the vegetative con- dition Family 2. Cryptomonadina. 98 ] The Classification of Lower Organisms 3. Amoeboid in the vegetative con- dition Family 3. Paramoebida. 2. Parasitic amoeboid organisms, the flag- ella of swimming stages respectively anterior and trailing Family 4. Paradinida. 1. Flagellate cells with two planes of symmetry Family 5. Nephroselmidacea. Family 1. Cryptococcacea [Cryptococcaceae] Pascher in Beih. Bot. Centralbl. 48, Abt. 2: 325 (1931). YdimWy Phaeocapsaceae West British Freshw. Alg. 48 (1904), in part; Phaeocapsa is a chrysomonad. Family Phaeoplakaceae Pascher 1. c. Solitary or clustered cells, non-motile in the vegetative condition, reproducing by flagellate cells of cryptomonad type. Phaeococcus, Cryptococcus, Phaeoplax. Chrysidella in- cludes yellowish cells called zooxanthellae, internally symbiotic in Radiolaria, Rhizo- poda, sponges, coelenterates, and rotifers. It is believed that the supposed zoospores of various amoeboid organisms are actually flagellate reproductive cells of Chrysi- della escaping at certain stages of the life cycles of their hosts. Family 2. Cryptomonadina Ehrenberg Infusionsthierchen 38 (1838). Family Chilomonadidae Kent Man. Inf. 1: 423 (1880). Family Cryptomonadaceae Engler Syllab. ed. 3: 7 (1903). Family Chilomonadaceae Lemmermann 1909. Family Cryptomonadidae Poche in Arch. Prot. 30: 159 (1913). Flagellate in the vegetative condition, the two flagella not markedly differentiated, springing from the anterior end of the cells, usually from the mouth of a pit lined by granules of some sort. Cryptomonas and Cryptochrysis have brown or yellow plastids; Chromomonas and Cyanomonas have blue ones; Rhodomonas has red ones. Chilomonas is a colorless saprophyte familiar in infusions. The colorless Cyathomonas, also from infusions, was shown by tJlehla (1911) to be related to Chilomonas. Family 3. Paramoebida [Paramoebidae] Poche in Arch. Prot. 30: 173 (1913). Schaudinn (1896) discovered the sole known species, Paramoeba Eilhardi, in an aquarium of sea water. It is an amoeboid organism with the peculiarity that each cell contains beside the nucleus an additional body which divides when the nucleus does. The cell may form about itself a shell of debris, and within this may undergo division into many cells which escape as pigmented swarmers resembling cells of Cryptomonas. Family 4. Paradinida [Paradinidae] Chatton in Arch Zool. Exp. Gen. 59: 444 (1920). The sole known species, Paradinium Poucheti, is a parasite in the body cavity of copepods. The amoeboid cells are linked together by slender pseudopodia so as to form a network. The reproductive cells have a shorter anterior flagellum and a longer trailing flagellum. Family 5. Nephroselmidacea [Nephroselmidaceac] Pascher Siisswasserfl. Deutsch- land 2: 'llO (1913). Family Nephroselmidae Calkins Biol. Prot. 267 (1926). Cells isobilateral. Cells disk-shaped, the flagella on the margin: Scnnia. Cells laterally extended, bean- or kidney-shaped, the indentation anterior and bearing the flagella: Protochrysis, Nephroselmis. Order 2. Adiniferidea Kofoid and Swczy in Mem. Univ. California 5: 108 (1921). Suborder Adinida Blitschli in Bronn Kl. u. Ord. Thicrreichs 1: 1001 (1885). Suborder Prorocentrinea Poche in Arch. Prot. 30: 160 (1913). Desmokontae, including Desmomonadales and Desmocapsales, Pascher in Ber. deutschen bot. Gess. 32: 158 (1914). Phylum Pyrrhophyta [ 99 Division Desmokontae; classes Desmomonadineae and Desmocapsineae; and orders Desmomonadales, Prorocentrales, and Desmocapsales Pascher in Beih. bot. Centralbl. 48, Abt. 2: 325 (1931). Suborder Prorocentrina Hall Protozoology 142 (1953). Solitary cells, mostly flagellate in the vegetative condition, the flagellate stages either naked or bearing a close wall of two valves, with two flagella at the anterior end, one extending forward while the other is bent circumferentially and causes the cell to whirl while swimming. The few known organisms of this group may be treated as a single family. Family Adinida Bergh in Morph. Jahrb. 7: 273 (1882). Family Prorocentrinen Stein Org. Inf. 3, II Halfte: 8 (1883). Family Prorocentrina Butschli in Bronn Kl. u. Ord. Thierreichs 1: 1002 (1885). Family Prorocentraceae Schiitt in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. lb: 6 (1896). Prorocentridae Kofoid in Bull. Mas. Comp. Zool. Harvard 50: 164 (1907). Family Prorocentridae Poche in Arch. Prot. 30: 160 (1913). Desmocapsa, Haplodiniuni, Desmomastix, Pleuromonas, Exuviaella, Prorocentrum; minute brown organisms, mostly marine. Order 3. CystoflageUata (Haeckel) Butschli in Bronn Kl. u. Ord. Thierreichs 1, Abt. 2, Inhalt (1887). Tribe [group of families] Gymnodinioidae Poche in Arch. Prot. 30: 161 (1913). Classes Rhizodininae, Dinocapsineae, Dinococcineae, and Dinotrichineae; orders Gymnodiniales, Rhizodiniales, Dinocapsales, Dinococcales, and Dinotrichales Pascher in Beih. bot. Centralbl. 48, Abt. 2 : 326 ( 193 1 ) . Suborders Gymnodinina, Dinocapsina, and Dinococcina Hall Protozoology 143, 147, 149 (1953). Haeckel ( 1866) made of Noctiluca alone a phylum under the name of Noctilucae. He had the carelessness, as it appears, to publish in the same work the synonymous phylar name Myxocystoda as a label in a phylogenetic diagram. In 1873 he used a third name, CystoflageUata, and Biitschli took this up; in the text of the Klassen und Ordnungen ambiguously as an Unterabtheilung or Ordnung, in the table of contents definitely as an order. Allman (1872) had shown that Noctiluca belongs to the present group. Biitschli did not agree with this opinion, but it is evidently correct, and Haeckel's name becomes the valid one for the order to which Noctiluca belongs Typical members of the present order are naked motile cells with brown plastids. The two flagella are attached near the equator of the cell. One of them extends in a posterior direction, in a groove called the sulcus. The other extends horizontally about the cell (generally to the right, in the reversed image seen in the microscope), lying in a groove called the girdle. The part of the cell anterior to the girdle is called the epicone, the part posterior to it, the hypocone. From the typical structure as thus described, there are, as will be seen, many deviations. The species, of which more than three hundred are known, may be treated as nine families. 1. Relatively unspecialized; having stages freely propelled by two flagella, with a single girdle, no tentacles, and unspecialized eyespots or none; not parasitic; commonly pigmented. 2. Walled and non-motile in the vegeta- tive condition Family 1. Phytodiniacea. 2. Flagellate in the vegetative condition Family 2. Gymnodiniacea. 100 ] The Classification of Lower Organisms 1. Not as above, always without photosynthetic pigments. 2. Amoeboid Family 3. Dinamoebidina. 2. Flagellate or free-floating. 3. With multiplied girdles, without tentacles or specialized light-sensi- tive organelles Family 4. PoLYKRiKroA. 3. With one girdle or none. 4. Cells more or less isodiamet- ric. 5. With prominent light-sen- sitive organelles, some- times with tentacles Family 5. Pouchetiida. 5. Without light-sensitive or- ganelles, with tentacles. 6. Not exceptionally large Family 6. Protodiniferida. 6. Reaching exceptional sizes, to 1 mm. in di- ameter Family 7. Noctilucida. 4. Cells dome-shaped Family 8. Lepodiscida. 2. Parasitic Family 9. Blastodinida. Family 1 . Phytodiniacea [Phytodiniaceae] Schilling in Pascher Siisswasserfl. Deutschland 3: 61 (1913). Family Phytodinidae Calkins Biol. Prot. 277 (1926). Dinocapsales, Dinocapsaceae, Dinococcales, Dinotrichales, and Dinotrichaceae Pascher in Ber. deutschen bot. Gess. 32: 158 (1914). Orders Dinocapsales, Dino- coccales, and Dinotrichales, and families Gloeodiniaceae, Hypnodiniaceae, Dino- trichaceae, and Dinocloniaceae Pascher in Beih. bot. Centralbl. 48, Abt. 2: 326 (1931). Organisms with numerous yellow to brown plastids, walled and non-motile in the vegetative condition, reproducing by gymnodinioid zoospores. Some fifty species are known; it is only recently that Thompson (1949) has found several of these in America. Cells multiplying in a gelatinous matrix: Gloeodinium. Cells solitary, dividing into several which escape usually in the flagellate condition; with smooth ellipsoid walls: Phytodinium, Stylodinium; anvil-shaped, stalked and with two horns: Racihorskya; tetrahedral, with horns at each comer: Tetradinium; with a ring of about six horns: Dinastridium. Tending to produce filaments; marine: Dinothrix, Dinoclonium. Family 2. Gymnodiniacea [Gymnodiniaceae] Schiitt in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. lb: 2 (1896). Subfamily Gymnodinida Bergh in Morph. Jahrb. 7: 274 (1882). Gymnodinidae Kofoid in Bull. Mus. Comp. Zool. Harvard 50: 164 (1907). Family Gymnodiniidae Poche in Arch. Prot. 30: 162 (1913). The typical unarmored dinoflagellates, free-swimming, with sulcus and girdle, without tentacles or a conspicuous light-sensitive organelle, commonly with photosynthetic pigments. The genus which is most numerous in species is Gymnodinium Stein. It includes both pigmented and non-pigmcnted species, mostly marine, occasional in fresh water, the girdles nearly equatorial and forming nearly complete circles. The cells readily become encysted, and the cysts may grow to large sizes, reaching diameters of 0.5 mm. These cysts have been taken for a distinct genus Pyrocystis. Observed in darkness, Phylum Pyrrhophyta [ 101 the protoplasm in the cysts is seen to become luminous in response to disturbance of the medium; they are among the agents of phosphorescence at sea. In Gymnodinium Lunula the protoplast of each large globular cyst undergoes division into several protoplasts which do not immediately become flagellate; each of them becomes crescent-shaped, deposits a cell wall, and is released by dissolution of the wall of the parent cyst. In the crescent-shaped cysts, the protoplasts divide into several which develop flagella and escape as typical gymnodinioid cells. In Hemidinium the girdle forms less than a complete circle; in Amphidinium, the girdle is close to the anterior end of the cell; in Gyrodinium, it forms a steep left spiral; in Cochliodinium it forms a left spiral of more than one and one half turns. Family 3. Dinamoebidina nom. nov. Order Rhizodiniales and family Amoehodi- niaceae Pascher (1931), not based on generic names. Non-pigmented amoeboid organisms producing crescent-shaped cysts which germinate by releasing gymnodini- oid zoospores. Dinamoebidium varians Pascher (1916; originally Dinamoeba, but there is an earlier genus of this name, and the author changed it). Family 4. Polykrikida [Polykrikidae] Kofoid and Swezy in Mem. Univ. California 5: 395 (1921). Family Polydinida Butschli (1885), not based on a generic name. There is a single genus Polykrikos, of only three known species. They are colorless predatory organisms of such a structure as might be produced if a cell of Gymnodi- nium were repeatedly to enter upon division and fail to complete it. Each elongate cell bears a single extended sulcus and a series of girdles; with each girdle are asso- ciated the usual two differentiated flagella. Of nuclei there are usually half as many as of girdles. The cells contain structures called nematocysts, whose development and structure was studied by Chatton (1914). Each nematocyst consists of a conical wall, with a peculiar operculum at the broad end, surrounding a minute cavity containing fluid and a coiled thread. Nematocysts are supposed to be homologous with trichocysts, and to contribute to protection, or to the capture of prey; the points seem not fully established. They occur only in this family and the following. Family 5. Pouchetiida [Pouchetiidae] Kofoid and Swezy in Mem. Univ. of Cali- fcrnia 5: 414 (1921). Each of the gymnodinioid cells contains a light-sensitive ap- paratus, the ocellus, consisting of a pigmented area and of one or more transparent globes, of unknown composition, serving as lenses. Most species have nematocysts. Protopsis, Pouchetia, etc.; Erythropsis, in warm seas, with a prominent tentacle. Family 6. Protodiniferida [Protodiniferidae] Kofoid and Swezy in Mem. Univ. California 5:111 (1921). Family Pronoctilucidae Lebour Dinofl. Northern Seas 10 (1925). Predatory organisms, the cells subglobular, without ocellus or nematocysts, but with a tentacle. Pronoctiluca Fabre-Domergue 1889 {Protodinifer Kofoid and Swezy 1921); 0.v}'rr/iw Dujardin. Description of the neuromotor apparatus and process of division in Oxyrrhis marina by Hall (1925) provides part of the authority for, and is in good conformity to, the remarks on mitosis included above in the description of the phylum. The nucleus contains a prominent internal body (endosome) which does not contain the material of the chromosomes and does not disappear during mitosis. A centrosome, close outside the nuclear membrane, is connected by two rhizoplasts to blepharo- plasts at the bases of the flagella. When a cell is to divide, the centrosome divides; the daughter centrosomes do not necessarily lie at the poles of the nucleus where the chromosomes assemble. Each daughter centrosome appears to generate one rhizoplast, blepharoplast, and flagellum to complete the neuromotor apparatus of a eel]. In due course, the endosome, nucleus, and cell undergo constriction. 102 ] The Classification of Lower Organisms Family 7. Noctilucida [Noctilucidae] Kent Man. Inf. 1: 396 (1880). The single species Noctiluca scintillans (Mackartney) Kofoid and Swezy (1921; usually known as A^. miliaris Suriray ) is a predatory marine organism, the subglobular cells reaching dimensions exceeding 1 mm., luminescent when stimulated and accordingly contrib- uting to phosphorescence at sea. Each cell is marked by an extensive depression representing the sulcus; the girdle is obsolete. A part of the area of the sulcus func- tions as a cytostome. A tooth in the sulcus represents the transverse flagellum. Present are a longitudinal flagellum, minute in proportion to the cell, and a prominent tentacle. Mitosis in Noctiluca has been studied by Calkins (1899), van Goor (1918), and Pratje (1921). Adjacent to the nucleus there is a body of differentiated cytoplasm, as large as the nucleus, called by Calkins the attraction sphere. Before mitosis, the tentacle and flagellum are absorbed. The attraction sphere becomes elongate and its central part becomes converted into fibers. The nucleus becomes appressed to, and curved about, the bundle of fibers, and the numerous elongate chromosomes assemble against this. The two curved margins of the nucleus draw apart along the bundle of fibers, appearing to draw the daughter chromosomes with them. Division is completed by constriction of the nucleus and disappearance of the fibers, leaving a daughter attraction sphere in association with each daughter nucleus. This peculiar mitotic process is probably of no phylogenetic significance, being, like the organism in which it occurs, an aberrant by-product of evolution. Nuclear division may be followed by division of the cell into two, the entire process requiring from twelve to twenty-four hours. Alternatively, the nucleus may divide repeatedly, each division requiring from three to four hours; the numerous nuclei produced are budded off from the cell in small uniflagellate spores. Ischikawa ( 1891 ) saw conjugation of pairs of cells, and van Goor stated that this is a preliminary to the production of spores; Pratje, on the other hand, could find no evidence of conjugation. The spores are believed to give rise by direct growth to cells like the original one. Family 8. Leptodiscida [Leptodiscidae] Kofoid 1905. Large dome-shaped preda- tory marine organisms with small flagella or none. Leptodiscus R. Hertwig (1877) was placed by Biitschli in order Cystoflagellata as the sole genus in addition to Noctiluca; Craspedotella is a comparatively recent discovery of Kofoid. Family 9. Blastodinida [Blastodinidae] Chatton in Arch. Zool. Exp. Gen. 59: 442 (1920). Ordre Blastodinides Chatton in Compt. Rend. 143: 981 (1906). Fam- ilies Apodinidae, Haplozoonidae, Oodinidae, and Syndinidae Chatton op. cit (1920). Dinoflagellates which are parasitic chiefly in copepods and tunicates, also in other animals and in diatoms. As a general rule, after the parasite has grown to a certain size, and a multiplication of nuclei has taken place, a part of the protoplast undergoes division to form gymnodinioid zoospores, while the remainder resumes growth in the host. Schizodinium, Blastodinium, Apodinium, Chytriodinium, etc. Order 4. CiUoflagellata Claparede and Lachman Etudes Inf. 1: 394 (1858). Family Peridinaea Ehrcnbcrg Infusionsthierchcn 249 (1838). Family Dinifera Bergh in MoVph. Jahrb. 7: 273 (1882). Order Dinoflagellata BiitschU in Bronn Kl. u. Ord. Thierreichs 1, Abt. 2: Inhalt (1887). Subclass Peridiniales Engler in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. lb: V (1896). Phylum Pyrrhophyta [103 Class Peridineae Wettstein Handb. syst. Bot. 1: 71 (1901). Division Dinoflagellata Engler Syllab. ed. 3: 8 (1903). Dinophyceae and Dinoflagellatae Pascher in Ber. deutschen bot. Gess. 32: 158 (1914). Order Diniferidea and tribe [group of families] Peridinioidae Kofoid and Swezy in Mem. Univ. California 5 : 106, 107 ( 1921 ) . Order Dinoflagellida Calkins Biol. Prot. 267 (1926). Division Dinophyceae, Class Dinoflagellatae, and order Peridiniales Pascher in Beih. bot. Centralbl. 48. Abt. 2: 326(1931). Suborder Peridinina Hall Protozoology 144 (1953). This order is very close to the preceding; its members are distinguished only by the presence, while the cells are in the flagellate condition, of cell walls, consisting in most examples of separable plates. The name Cilioflagellata is evidence of an early error of observation: the circumferential flagellum was mistaken for a whorl of cilia. This name and most of its synonyms were published as applying both to the preceding order and this. For almost all of these names the type or obvious standard example is Peridinium, with the effect that the names belong to the present order. There are about five hundred species, prevalently marine. Five families may be recognized. Family 1. Peridinaea Ehrenberg Infusionsthierchen 249 (1838). Family Peridin- idae Kent Man. Inf. 1: 441 (1880). Family Peridiniaceae Schiitt in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. lb: 9 (1896). Ceratiidae Kofoid in Bull. Mus. Comp. Zool. Harvard 50: 164 (1907). The typical dinoflagellates, of numerous genera and species. The distinctions among them are largely matters of the detailed arrangement of the plates making up the walls. Glenodinium, the plates scarcely distinguishable. Peridinium, Goniodoma, Goniaulax, Ceratium, Oxytocum, etc. The cells of certain species in various genera are ornamented with prominent horns; in Ceratium especially the epitheca is drawn out into one long horn, and the hypotheca into one, two, or three. Goniaulax becomes abundant at certain seasons, is eaten by shellfish, and renders them poisonous. The neuromotor apparatus (much as in Menoidium) and the process of nuclear and cell division in Ceratium Hirundinella were described by Entz (1921) and Hall (1925). Many nuclei lack the endosome; if present, it disappears during mitosis, as does also the nuclear membrane. The daughter centrosomes lie at the sides of the blunt-ended mitotic figure. When nuclear division is complete, the protoplast ex- pands and then becomes constricted in such fashion that each daughter cell receives certain plates of the wall; each daughter cell then secretes the plates which it lacks. Zederbauer (1904) reported conjugation in Ceratium. He saw an elongate proto- plast with each of its ends covered by a complete cell wall. Dividing cells are of quite different appearance. Families Ptychodiscida, Cladopyxida, and Amphilothida of Kofoid (1907, the names in the feminine; explicitly made families by Poche, 1913) are minor segregates from Peridinaea. Family 5. Dinophysida (Bergh) Biitschli in Bronn Kl. u. Ord. Thierreichs 1: 1009 (1885). Subfamily Dinophysida Bergh in Morph. Jahrb. 7: 273 (1882). The limits of the plates obscure; girdle near the anterior end; sulcus and girdle bordered by prominent flanges. Strictly marine, mostly in warmer oceans. Dinophysis, Oxyphy- sis, Amphisolenia, Triposolenia, etc. 104] The Classification of Lower Organisms Fig. 19, — a, Tetradinium javanicum x 1,000 after Thompson (1949). b, Gytnno- dinium striatum x 500 after Kofoid & Swezy (1921). C, Gymnodiniian Lunula, flagellate cells forming in a cyst x 500, after Kofoid & Swezy op. cit. d, e, f, Din- amoehidium varians; amoeboid vegetative cell, cyst, and production of gymnodinioid zoospores x 1,000 after Pascher (1916). g, Noctiluca scintillans x 100 after Allman (1872). h, Peridinium cinctum x 1,000. i, Triposolcnia Ambulatrix x 500 after Kofoid (1907). j, Amphisolcnia laticincta after Kofoid, op. cit. Phylum Pyrrhophyta [ 105 Order 5. Astoma Siebold in Siebold and Stannius Lehrb. vergl. Anat. 1 : 10 ( 1848) . Order Phytozoidea Perty Kennt. kleinst. Lebensf. 161 (1852), in part. Order Flagellata Claparede and Lachmann Etudes Inf. 1: 73 (1858), in part. Order Flagellato-Eustomata Kent Man. Inf. 1: 36 (1880). Suborder Euglenoidina Biitschli in Bronn Kl. u. Ord. Thierreichs 1 : 818 ( 1884). Abtheilung (suborder) Chloromonadina Klebs in Zeit. wiss. Zool. 55: 391 (1893). Order Euglenoidina Blochmann Mikr. Tierwelt 1, ed. 2: 50 (1895). Subclasses Chloromonadineae and Euglenineae Engler in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. la: v, vi (1900). Orders Euglenales and Chloromonadales Engler Syllab. ed. 3: 7 (1903). Orders Eugleninae and Chloromonadinae Pascher Siisswasserfl. Deutschland 1 : 29 (1914). Orders Euglenida and Chloromonadida Calkins Biol. Prot. 283, 285 (1926). Mostly solitary flagellate cells of fresh water, unwalled and capable of contraction and writhing movement; the anterior end of each cell (in the flagellate condition) penetrated by a pit, the reservoir or cytopharynx, into which contractile vacuoles open; having one flagellum, or two, usually unequal, or more, one flagellum of each cell usually being stichoneme; mostly producing a solid storage product, not staining blue with iodine, called paramylum. Jahn (1946) reviewed this group. He recognized four families, to which one more, to include the chloromonads, is to be added. 1. Producing paramylum. 2. Flagellum with a swelling near the base, usually single but formed of two parts which join below the swelling; cells mostly pigmented. 3. Non-motile and walled in the vege- tative condition Family 1 . Colaciacea. 3. Flagellate in the vegetative con- dition Family 2. Euglenida. 2. Flagellum not swollen and usually not forked near the base; cells not pig- mented. 3. Cells without internal rod-shaped structures; flagella stichoneme Family 3. Astasiaea. 3. Cells with internal rod-shaped struc- tures; flagella acroneme or simple Family 4. ANisoNEMroA. 1. Not producing paramylum, storing oil Family 5. Coelomonadina. Family 1. Colaciacea [Colaciaceae] Smith Freshw. Alg. 617 (1933). Family Colaciidae Jahn in Quart. Rev. Biol. 21: 264 (1946). Euglenoid organisms which are walled and non-motile in the vegetative condition. There is a single genus Colacium, producing dendroid colonies. Family 2. Euglenida Stein Org. Inf. 3, I Halfte: x (1878). Family Euglenina Biitschli in Bronn Kl. u. Ord. Thierreichs 1: 820 (1884). Family Euglenaceae Engler in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. 2: 570 (1897). Solitary motile cells, mostly with abundant green plastids, the flagella with swellings near the base, mostly solitary and forked below the swelling. Jahn recognized twelve genera. Eutreptia has two flagella; Euglenamorpha has three. Members of the latter genus 106] The Classification of Lower Organisms Fig. 20. — a., Colacium Arbuscula after Stein (1878). b^ Euglena viridis. c, Eu- glena Spirogyra. d, Euglena acus. e, Phacus sp. f, Trachelomonas sp. g, Kleb- siella alligata after Pascher (1931). All x 1,000. Phylum Pyrrhophyta [ 107 are entozoic in frog tadpoles; some of them are non-pigmented. Three genera having the typical single flagella are among the most familiar of flagellates. Euglena has fusiform to cylindrical cells freely capable of writhing changes in shape. Phacus has flattened cells with a rigid membrane. In Trachelomonas, the protoplast lies loose in a rigid lorica which is often ornamented with spines; variations in the form and ornamentation of the lorica have made it possible to distinguish a large number of species. There are accounts of mitosis in Euglena by Keuten (1895), Baker (1926), Rat- cliffe (1927) and Hall and Jahn (1929). All observers have seen within the nucleus a large globule which divides as the nucleus does and appears to guide the separating chromosomes. Keuten applied to it the term nucleolo-centrosome; the implications of this term are not confidently to be accepted, and the body will better be called by the neutral term endosome. RatclifTe's account of mitosis in Euglena Spirogyra is the most detailed. It appears that division is initiated when the endosome buds oflE a small granule which migrates to a position just within the nuclear membrane and divides. The resulting granules may be regarded as centrosomes. The nucleus moves forward within the cell and comes into contact with the cell membrane at the bottom of the reservoir. Each centrosome appears to generate, just within the cell membrane, a granule recognizable as a blepharoplast; the nucleus then withdraws from the cell membrane, but the centrosomes remain connected to the blepharoplasts by rhizo- plasts. The flagellum, already split at the base, divides throughout its length into two; a new flagellum-base grows out from each blepharoplast and becomes fused to one of the halves of the old one not far from the base of the latter. Meanwhile, withm the intact nuclear membrane, the chromosomes and endosome are dividing. The centrosomes are at the sides of the dividing nucleus. No spindle has been recognized. Nuclear division is completed by constriction of the membrane. The cell divides by constriction which proceeds longitudinally from the anterior end. The centrosomes and rhizoplasts disappear, to be replaced during the next division by new ones. Hall and Hall and Schoenborn (in several papers, 1938, 1939) have reported experiments on nutrition in Euglena. All species are capable of photosynthesis. Some of them, surprisingly, have lost the capacity to synthesize amino acids which usually accompanies photosynthesis; and there are transitional species in which some in- dividuals possess the capacity to make amino acids and others do not, evidently as heritable characters. Family 3. Astasiaea Ehrenberg Infusionsthierchen 100 (1838). Family Astasiidae Kent Man. Inf. 1 : 375 ( 1880) . Family Astasiina Biitschli in Bronn. Kl. u. Ord. Thier- reichs 1 : 826 ( 1884) . Family Astasiaceae Senn in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. la: 177 (1900). Colorless organisms. Deflandre found the flagella sticho- neme, as to the single flagella of Astasia and Menoidium, and as to one of the two flagella of Distigma. Hall and Jahn (1929) found the flagella not swollen near the base. The internal rod-shaped structures which characterize the following family are absent. Belar (1915) described mitosis in Astasia, and Hall (1923) described it in Menoidium. There is a blepharoplast at the base of the flagellum, and some prepara- tions show a rhizoplast connecting this to a centrosome immediately outside the nuclear membrane. The blepharoplast divides during the early stages of mitosis, and the flagellum appears to divide lengthwise. The daughter centrosomes mark the loci toward which the dividing chromosomes move. The chromosome number appears to be 12. A dividing endosome like that of Euglena is present. 108] The Classification of Lower Organisms Scytomonas pusilla Stein {Copromonas subtilis Dobell) occurs in the intestines of frogs and toads. When cast out with the feces, it exhibits conjugation as a pre- liminary to encystment (Dobell, 1908). Family 4. Anisonemida [Anisonemidae] Kent Man. Inf. 1: 429 (1880). Families Pernamina and Anisonemina Biitschli in Bronn Kl. u. Ord. Thierreichs 1 : 824, 828 (1884). Family Peranemaceae Senn in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. la: 178 (1900). Family Heteronemidae Calkins Biol. Prot. 285 (1926). Each cell of these colorless organisms bears one conspicuous anterior flagellum; most of them bear also a less conspicuous trailing flagellum. The trailing flagellum of Pera- nema is grown fast to the cell membrane, and is detected only with difficulty (Hall, Fig. 21.— a, Menoidium incurvum. b, c. Stages of mitosis in Menoidium incurvum X 2,000 after Hall (1923). d, e, Peranema trichophorum. i, Stage of division in Peranema trichophorum after Hall (1934). g, Anisoncma truncatum. h, Ento- sipon sulcatum, i-m, Vacuolaria viridis: i, cell; j, neuromotor apparatus after Fott (1935); k-m, stages of mitosis x 2,000 after Fott, op cit. x 1,000 except as noted. Phylum Pyrrhophyta [ 109 1934). Deflandre was unable to find appendages on the flagella of members of this family. As in other members of the order, the flagella spring from a deep anterior pit in the cell; in this family, the pit is a functional cytopharynx (Hall, 1933). The cyto- plasm of Peranema contains three brief rods, the pharyngeal rods or Staborgane, lying near the cytopharynx; their function is unknown. Each cell of Urceolus, of Anisonema, and of Heteronema contains a single conspicuous rod extending the length of the body. Hall and Powell (1928) and Hall (1934) described the mitotic process in Peranema, which is much as in Menoidium. Family Coelomonadina Butschli in Bronn Kl. u. Ord. Thierreachs 1 : 819 (1884). Family Vacuolariaceae Luther in Bihang Svensk. Vetensk-Akad. Handl. 24, part 3, no. 13: 19 (1889). Family Chloromonadaceae Engler Syllab. ed 3: 7 (1903). Family Thaumatonemidae Poche in Arch. Prot. 30: 155 (1913). Family Chloromonadidae HoUande in Grasse Traite Zool. 1, fasc. 1: 235 (1952); family Thaumatomonadidae Hollande op. cit. 686. Unicellular organisms, mostly green, with two diiTerentiated flagella springing from a large reservoir, producing globules of oil but no solid storage product. Klebs apologized for erecting the grossere Abtheilung Chloromonadina for the single genus Vacuolaria, and in fact, this genus differs from other members of the present order only in one conspicuous character, the failure to produce paramylum. Fott (1935) studied the cytology of Vacuolaria. From the base of each flagellum, a rhizoplast extends into the cytoplasm, but fails to come into contact with the nucleus. Several granules or swellings, not definitely identifiable as blepharoplasts or centro- somes, are distributed along the length of each rhizoplast. In mitosis, which takes place within an intact nuclear membrane, the numerous subglobular chromosomes form a blunt-ended figure much as in Chilomonas. Genera believed to be allied to Vacuolaria include the green flagellate Goniostomum; Chysophaeum Lewis and Bryan (1941), a marine organism forming non-motile yellow dendroid colonies of m.acroscopic dimensions; and the colorless flagellate Thaumatomastix Lauterborn (originally named Thaumatonema, but there is among plants an older genus of this name). Chapter VHI PHYLUM OPISTHOKONTA Phylum 4. OPISTHOKONTA, phylum novum Chytridieae de Bary in Bot. Zeit. 16, Beil. 96 (1858). Family Chytridieen de Bary and Woronin (1864). Family Chytridiaceae Cohn in Hedwigia 11: 18 (1872). Chytridineae Schroter in Engler and Frantl Nat. Pflanzenfam. I Teil, Abt. 1 : 62 (1892). Series (Reihe) Archimycetes (Chytridinae) A. Fischer in Rabenhorst Kryp- tog.-Fl. Deutschland 1, Abt. 4: 11 (1892). Suborders Chrytidiineae and Monoblepharidineae Engler in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. 1: iii, iv (1897). Order Chytridineae Campbell Univ. Textb. Bot. 152 (1902). Classes Archimycetae and Monoblepharideae Schaff'ner in Ohio Naturalist 9: 447,449 (1909). Class Archimycetes Gaiimann Vergl. Morph. Pilze 15 (1926). Uniflagellatae Sparrow Aq. Phyc. 21 (1943). Parasites and saprophytes of simple structure (filamentous, of uniform diameter or tapering; or unicellular, with or without rhizoids, i. e. tapering filamentous out- growths), with cell walls of chitin, containing no cellulose; producing motile cells with solitary posterior acroneme flagella. Type, Chytridium Olla Braun. From 6tt[o9ioc;, rearward, and KOVT6q^oar. Chytrid is the English form of the generic name Chytridium, from Greek )(UTp(<;, a jug. Braun (1856) applied this name to a colorless unicellular organism found attached to green algae whose cells are penetrated by rhizoids which draw food from them and kill them. By chytrids we mean organisms of body types of the general nature of that of Chytridium. All such organisms were formerly treated as a single taxonomic group. Couch (1938, 1941) showed that the organisms of chytrid body type form three markedly distinct groups distinguished by types of flagellation. The proper chytrids, those which legitimately constitute a taxonomic group, are marked by swimming cells with solitary posterior acroneme flagella, and further by lack of cellulose in the cell walls. The group thus marked includes, beside organisms of chytrid body type, a few organisms of the filamentous body type of the typical fungi. The cytoplasm of members of this group is described as peculiarly lustrous and as containing shining globules. In mitosis (seen repeatedly, as by Dangeard, 1900, Stevens and Stevens, 1903, Wager, 1913, and Karling, 1937), the sharp-pointed spindle forms within the intact nuclear membrane. Some observers have seen centro- somes at the poles. The nuclear membrane disappears toward the end of the process. The formation of motile cells (zoospores and sometimes gametes) occurs in en- larged cells. In these cells there are repeated simultaneous nuclear divisions. After the last of these, uninucleate protoplasts, each one containing, ordinarily, one of the above-mentioned shining globules, are separated by cleavage. On each of these protoplasts a flagellum grows from the cell membrane at the point nearest that part of the nucleus which represents a pole of the previous mitotic spindle. Among the Blastocladiacea, the nucleus lies against the cell membrane and the flagellum appears to spring from a granule within it (Cotner, 1930; Hatch, 1935). Similarly, in Clado- Phylum Opisthokonta [111 chytrium, it appeared to Karling (1937) that the nucleolus generates the flagellum. Within the developing swimming cell a body of granules assembles and produces a "cap," prominent in stained material, on the anterior side of the nucleus, that is, on the side away from the flagellum. Nowakowski (1876) observed sexual processes in Polyphagus, and Scherffel (1925) observed them in many other chytrids. Sexual processes were known in Monoblepharis from the discovery of this genus, and have been studied in detail in Allomyces by Emerson (1939, 1941) and Emerson and Wilson (1949). The group thus characterized is of fewer than three hundred known species. One takes no satisfaction in making it a phylum, but feels constrained to do so by its isolation. Note has been taken that other groups including organisms of chytrid body type, as Hyphochytrialea, Lagenidialea, and Phytomyxida, have nothing to do with the proper chytrids. Furthermore, it will not do to thrust the proper chytrids in with the groups of colorless flagellate and amoeboid organisms treated below as phylum Protoplasta. One does not trust that group as natural, but it has a morpo- logical continuity which would be defaced by the addition of this one. Vischer, 1945, coined the name Opistokonten for organisms whose motile cells have posterior flagella. Gams (1947) listed as such the green organisms Pedilomonas and Chlorochytridion; the choanoflagellates; the proper chytrids; the Sporozoa (the whole group by virtue of such examples as have flagellate stages); and the proper animals. He inferred that these groups make up a major natural group derived from the lowest green algae. This interesting hypothesis must as yet be treated as far-fetched. Pedilomonas is scarcely known; it was described by Korschikoff, 1923, as a green flagellate of somewhat the appearance of a Chlamydomonas lacking one of its flagella. The flagella of the choanoflagellates are pantacroneme instead of acro- neme. There remains a striking resemblance between the motile cells of the proper chytrids and the sperms of animals. The nuclear cap of the former is quite similar, in development and structure, to the beak of the latter. The Opisthokonta are reasonably treated as a single class. Class ARCHIMYCETES (A. Fischer) SchaflFner Synonymy of the phylum. Characters of the phylum. Previous authors have arranged these organisms in a sequence from strictly uni- cellular forms to typically filamentous forms. In the following treatment, this sequence is reversed. The course of the evolution of the group is unknown, and it seems reason- able to place the body types in the same sequence as among the Oomycetes. The class is treated as two orders, Monoblepharidalea, essentially filamentous, and Chytridinea, unicellular or producing filaments which taper or are swollen at intervals. Order 1. Monoblepharidalea [Monoblepharidales] Sparrow in Mycologia 34: 115 (1942). Suborder Monoblepharidineae Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. 1: iv (1897). Blastocladiincae Petersen in Bot. Tidsskr. 29: 357 (1909). Order Blastocladiales Sparrow 1. c. Opisthokonta whose bodies consist of filaments of uniform diameter, or are of types apparently immediately derived from this. Saprophytes in fresh water or soil, chiefly on vegetable remains. There are two families. 112 ] The Classification of Lower Organisms Family 1. Monoblepharidacea [Monoblepharidaceae] A. Fischer in Rabenhorst Kryptog.-Fl. Deutschland 1, Abt. 4: 378 (1892). Gonapodiineae and Gonapodiaceae Petersen in Bot. Tidsskr. 29: 357 (1909). Producing extensive coenocytic filaments, non-septate but with false septa of cytoplasm, anchored by rhizoids, reproducing asexually by zoospores produced in sporangia which are usually terminal on the filaments, the gametes produced in smaller antheridia and larger oogonia which are in the more familiar forms terminal and subterminal on the filaments, the branches commonly proliferating below them, the eggs without flagella. The species, about a dozen, form three genera. In Monoblepharis, the zygote, being the entire protoplast of the oogonium, moves out of the oogonium through a terminal pore, becomes attached in the opening, and develops a thick wall. In Monoblepharella the zygote, retaining the flagellum of the sperm, swims for a time before becoming encysted. Gonapodya resembles Monoblepharella (Johns and Ben- jamin, 1954). Myrioblepharis Thaxter is believed not to be an organism; it is de- scribed as something which might be produced if sporangia of Monoblepharis were parasitized by an infusorian. Family 2. Blastocladiacea [Blastocladiaceae] Petersen in Bot. Tidsskr. 29: 357 (1909). Coenocytic filaments, in some examples of a false appearance of septation, of the body type of the Rhipidiacea, i. e., differentiated into a basal cell anchored by rhizoids and distal branches bearing reproductive structures, sometimes so re- duced that the basal cell bears, or is itself, the reproductive structure; the reproduc- tive structures including thin-walled zoosporangia, thick-walled resting spores which germinate by releasing zoospores, and gametangia; the gametes morphologically uniform or larger and smaller, all bearing flagella. These organisms are not familiar, although they are readily isolated by baiting pond water, or tap water to which soil has been added, with hemp seeds or pieces of fruit. There are four genera, Allomyces, Blastocladia, Blastocladiella, and Sphaero- cladia, with about twenty-five known species. Allomyces is of interest for varied life cycles, and Blastocladia for a peculiar type of metabolism. The first known species of Allomyces, A. Arbuscula, was discovered by Butler (1911) on dead flies in water in India. The individuals are of the appearance of minuscule shrubs, the branches divided by pseudosepta punctured in the middle and ending in series of varicolored reproductive structures. Ordinary sporangia are colorless, resting spores are brown, mature antheridia are pink, and mature oogonia dull gray. Kniep (1929), in discovering the second species, A. javanicus, found that the individuals are of two types, one bearing sporangia and resting spores, the other oogonia and antheridia. Thus this organism has a complete life cycle of morpholo- gically homologous haploid and diploid individuals. Kniep supposed that meiosis occurs in the resting spores, and Emerson and Wilson (1949) established the point. The chromosome number (n) oi A. Arbuscula is 7; that of A. javanicus var. macro- gynus and of A. cystogenes is 14. The life cycle of A. Arbuscula is the same as that of A. javanicus. In A. cystogenes, the haploid stage consists merely of the zoospores from the resting spores; these become encysted and germinate by releasing isogametes. Thus this species has a life cycle essentially of the advanced type characteristic of animals. There are further species of Allomyces in which a sexual cycle is believed not to occur. In Blastocladia the basal cell bears directly multiple reproductive structures. Organisms of this genus are less easily cultured than Allomyces; they require several vitamins of the B group (Cantino, 1948). They tolerate oxygen, but do not require it. Phylum Opisthokonta [113 They convert sugars to lactic and succinic acids, producing no CO2; the acids, if not neutralized, check the growth of cultures (Emerson and Cantino, 1948; Cantino, 1949). Blastocladia appears to have lost the capacity to carry on the aerobic stages of energesis, thus reverting to the type of metabolism characteristic of the supposedly most primitive bacteria. In Blastocladiella, the basal cell bears a single reproductive structure. DiflFerent species have the same three types of life cycle which occur in Allomyces (Couch and WhiflFen, 1942). In Sphacrodadia the vegetative body is reduced to the unicellular condition which is characteristic of the following order rather than of this. The life cycle is of the complete homologous type. Order 2. Chytridinea [Chytridineae] (Schroter) Campbell Univ. Textb. Bot. 152 (1902). Orders Myxochytridinae and My cocky tridinae A. Fischer in Rabenhorst Kryp- tog. Fl. Deutschland 1, Abt. 4: 20, 72 (1892), not based on generic names. Order Chytridiales Auctt. Further synonymy as of the name of the phylum. Opisthokonta which consist entirely or largely of more or less isodiametric bodies called centers: the centers may send out filaments more slender than themselves, generating at their ends further centers; or may be capable only of producing rhizoids, i. e., tapering absorptive filaments; or may be by themselves complete individuals. The chytrids are commonly thought of as prevalently parasitic on algae and higher plants. They attack also rotifers, insects, nematodes, and other minute animals; some parasitize other chytrids (Karling, 1942, 1948). It is probable, however, that the majority of the group are saprophytic on organic remains. Some have been cultured with no other organic food than cellulose (Haskins, 1939); new forms have been discovered by baiting with, and culturing on, chitin (Karling, 1945; Hanson, 1946) or keratin (Karling, 1946, 1947). The following varieties of vegetative structure may be noted, (a) A zoospore, settling upon the surface of an appropriate host or substratum, may penetrate this by means of a walled filament which develops a terminal center; the center then sends out rhizoids, and also filaments which generate further centers, (b) Develop- ment may be as above except that only one center is formed. The body thus described is of the Entophlyctis type of Sparrow (1943). (c) The zoospore may itself become the single center, penetrating its host or substratum only by rhizoids. The resulting body is of the Chytridium type if the center is in contact with the host or substratum, of the Rhizidium type if it is not. (d) The protoplast of the zoospore may migrate into the protoplast of the host and there become a center without rhizoids; the resulting body is of the Olpidium type. To the varied bodies thus described, the following terminology is applicable: Pluricentric, with more centers than one; mono centric, with a single center. Intramatrical, the center developing within the substratum or host; alternatively, in a host, endobiotic. Extramatrical or epibiotic, contrary to the foregoing. Eucarpic, the center not constituting the entire body; holocarpic, the center con- stituting the entire body. The center regularly remains uninucleate during the vegetative phases and then becomes the seat of successive simultaneous nuclear division, of cleavage, and of the maturation of zoospores. Thus it is converted into a sporangium. In many forms, the 114] The Classification of Lower Organisms Fig. 22. — Monoblepharidalea: a-f, M o noble pharella Taylori x 1,000 after Springer (1945); a, germinating spore producing a filament and a rhizoid; b, spor- angium releasing spores; c, empty antheridium and sperm uniting with egg; d, sperms escaping from antheridium and zygote escaping from oogonium; e, swimming zygote; f. encysted zygote, g-i, Allomyces javanicus x 100 after Kniep (1929); g, asexual (Continued bottom p. 115) Phylum Opisthokonta [115 proximal part of the system of rhizoids develops a large swelling called the apo- physis. In other forms, the center generates the sporangium as an outgrowth. In these circumstances, the center is sometimes called an apophysis, but were better called a presporangium. The sporangium discharges its spores, usually, through one or more tubes which grow forth from it. The tube may open through a difTerentiated cap, the operculum; the production of opercula appears to mark a natural subordi- nate group. Syngamy occurs in different chytrids in most of the possible fashions, by union of like or unlike swimming cells, by the union of a swimming cell with a stationary one, or by the establishment of contact by growth. The zygote regularly becomes a thick- walled resting spore (asexual resting spores are also of frequent occurrence). Resting spores germinate by producing zoospores. Meiosis has not been observed, but is be- lieved to occur during the first nuclear divisions in the germinating zygote; the life cycle is apparently of the primitive type, in which all cells except the zygote are haploid {Phy so derma, or at least some of its species, is believed to be exceptional). Sparrow (1943) recognized nine families. One of these does not appear tenable; the remainder are distinguished as follows: 1. Sporangia not opening through opercula. 2. Eucarpic, i. e., producing rhizoids and sometimes other filaments, the centers not constituting the entire body. 3. Pluricentric Family 1. Cladochytriacea. 3. Monocentric. 4. Germinating spores generat- ing the center as a distinct body Family 2. Phlyctidiacea. 4. Zoospores themselves becom- ing centers, and subsequently sporangia or presporangia Family 3. Rhizidiacea. 2. Holocarpic, i. e., without rhizoids, the individual consisting entirely of one or more centers. 3. Centers becoming presporangia, each one generating a cluster of sporangia Family 4. Synchytriacea. 3. Centers proliferating, giving rise to linear series of sporangia Family 5. Achlyogetonacea. 3. Each center becoming one spor- angium Family 6. Olpidiacea. individual with light sporangia and dark resting cells with pitted walls; h, branch of sexual individual, the oogonia larger and darker than the antheridia; i, gametes. j-m, Allomyces Arbuscula after Hatch (1935); j, k, gametes, x 1,000; 1, m, mitotic figures in the gametangia, x 2,000. n-r, Blastocladiella cystogena, x 500, after Couch and WhifFen (1942); n, individual producing a resting spore; O, resting spore germ- inating by release of numerous naked protoplasts; these become flagellate zoospores, p, which subsequently encyst; q, the protoplast of each cyst divides to produce four gametes; r, young zygote with the flagella of both gametes. 116] The Classification of Lower Organisms ' B^^ fiG. 23. — Chytridinea: a-c, Polyphagus Euglenae attacking cells of Euglena, X 400, after Nowakowski (1876); in figure b, two individuals have made contact and a zygote is developing at the point of junction; c, sporangium, d-i, Olpidium Allomycetos attacking Alomyces anomalus, x 1,000, after Karling (1948); d, e, zoo- spores; f, sporangium of the host beset with many parasites; g, h, resting cells of the host containing respectively sporangia and resting cells of the parasite; i, germina- tion of resting cell. Phylum Opisthokonta [117 1. Sporangia opening through opercula. 2. Pluricentric Family 7. Nowakowskiellacea. 2. Monocentric Family 8. Chytridiacea. Family 1. Cladochytriacea [Cladochytriaceae] Schroter in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. 1: 80 (1892). Family Hyphochytriaceae [Cladochytria- ceae) A. Fischer in Rabenhorst Kryptog.-Fl. Deutschland 1, Abt. 4: 131 (1892), in part. Family Physodermataceae Sparrow Aq. Phyc. 304 (1943). Pluricentric chytrids, the sporangia not operculate. The members of this family are of the same body type (designated by Karling, 1931, the rhizo mycelium) as the anisochytrid Hyphochy- trium and the Nowakowskiellacea of the present order. In most Cladochytriacea the rhizomycelium includes pairs of swollen cells ("turbinate organs") which give a false appearance of conjugation. There are some forty known species, mostly of two genera, Cladochytrium, saprophytic in vegetable remains, and Physoderma (including Urophlyctis), parasitic in higher plants. Sparrow (1946, 1947) discovered in certain species of Physoderma an alternation of morphologically distinguishable generations, both on the same hosts; the generations are presumably haploid and diploid, but this has not been established by observation of syngamy and meiosis. Polychytrium grows well only on chitin (Ajello, 1948). Family 2. Phlyctidiacea [Phlyctidiaceae] Sparrow in Mycologia 34: 114 (1942). Family Sporochytriaceae [Rhizidiaceae, Polyphagaceae) subfamily Metasporeae A. Fischer in Rabenhorst Kryptog.-Fl. Deutschland 1, Abt. 4: 85 (1892). Monocentric eucarpic chytrids, the centers developed at the ends of filaments which grow from the zoospores, sporangia without opercula. These are the most familiar chytrids. There are more than one hundred species. Many are parasitic, on blue-green and green algae, diatoms, pollen grains, nematodes, and other minute fresh-water life; others are saprophytic, on cellulose, chitin, or keratin. Rhizophidium, the most numerous genus; Phlyctidium, Phlyctorhiza, Ento- phlyctis, Diplophlyctis, Loborhiza, etc. Family 3. Rhizidiacea [Rhizidiaceae] Schroter in Engler and Prantl Nat. Pflanzen- fam. I Teil, Abt. 1: 75 (1892). Family Sporochytriaceae [Rhizidiaceae, Polyphaga- ceae) A. Fischer in Rabenhorst Kryptog.-Fl. Deutschland 1, Abt. 4: 85 (1892) and subfamily Orthosporeae op. cit. 124. Monocentric eucarpic chytrids, the zoospores enlarging and becoming centers, which in turn become sporangia or presporangia; the sporangia without opercula. A moderate number of species, parasitic on blue-green or green algae, flagellates, or diatoms; or chitinophilous, saprophytic in the shed exoskeletons of insects. Rhizidium, Siphonaria, Asterophlyctis, Polyphagus, etc. Polyphargus Euglenae Nowakowski (1876) is a classic example. The centers lie free in the water, parasitizing cysts of Euglena through freely branching and widely spreading rhizoids. Most centers act as presporangia. Syngamy occurs when a rhizoid from one center makes contact with another center. The protoplasm of the latter migrates into the tip of the rhizoid, which swells and becomes a resting spore. Family 4. Synchytriacea [Synchytriaceae] Schroter op. cit. 71. Family Merol- pidiaceae [Synchytriaceae) A. Fischer op. cit. 45. Holocarpic chytrids, the intra- matrical cell unwalled in the vegetative condition, becoming a presporangium or a resting spore, either of which gives rise to a cluster of sporangia. Synchytrium, parasitic on higher plants; Micromycopsis on Conjugatae. Family 5. Achlyogetonacea [Achlyogetonaceae] Sparrow in Mycologia 34: 114 (1942). Chytrids without rhizoids, the intramatrical center proliferating and pro- ducing a linear series of centers, each of which becomes a sporangium without an 118] The Classification of Lower Organisms operculum. Achlyogeton, in green algae, diatoms, and nematodes; of very much the appearance of certain Lagenidialea. Family 6. Olpidiacea [Olpidiaceae] Schroter op. cit. 67. Family Monolpidiaceae [Olpidiaceae) A. Fischer op. cit. 20. Holocarpic chytrids, each individual a single intramatrical parasitic center, naked until the reproductive phase, when it becomes a sporangium without an operculum. Olpidium, attacking blue-green and green algae, diatoms, flagellates, Allomyces, Vampyrella, rotifers, and nematodes. Rozella, attack- ing Oomycetes and producing spiny resting spores, has been confused with certain Lagenidialea. The genera Sphaerita and Nucleophaga of Dangeard, including intracellular parasites of amoebas and Infusoria, have been placed in this family; it seems more probable that they should be placed among bacteria of family Rickett- siacea. Family 7. Nowakowskiellacea [Nowakowskiellaceae] Sparrow in Mycologia 34: 115 (1942). Family Megachytriaceae Sparrow Aq. Phyc. 378 (1943). Pluricentric chytrids, the sporangia with opercula. A moderate number of saprophytes on material of green algae and higher plants. Nowakowskiella, Megachytrium, etc. Zygochytrium was described by Sorokin, 1874, as living on decaying insects, producing multiple operculate sporangia, and exhibiting a conjugation of filaments to produce zygotes much like those of Zygomycetes. It has apparently not been reobserved. Family 8. Chytridiacea [Chytridiaceae] Cohn in Hedwigia 11: 18 (1872). Family Chytridieen de Bary and Woronin in Berichte Verhandl. Naturf. Gess. Freiburg 3 (Heft 2) : 46 ( 1864). Monocentric eucarpic chytrids, the sporangia operculate. Some fifty species, the majority parasitic on fresh water algae. Chytridium, etc. Catenochy- tridium, saprophytic in cast-off exoskeletons of insects. Chapter IX PHYLUM INOPHYTA Phylum 5. INOPHYTA Haeckel Order Fungi L. Sp. PI. 1 1 7 1 (1 753 ) . Hysterophyta Link, 1808. Classes Fungi and Lichencs Bartling Ord. Nat. 4 (1830). Regnum Mycetoideum Fries Syst. Myc. 1: Ivi (1832). Class Lichenes and section Hysterophyta with class Fungi Endlicher Gen. PI. 11, 16 (1836). Stamm Inophyta Haeckel Gen. Morph. 2: xxxvi (1866). Subdivision Fungi Engler and Prantl Nat. Pflanzenfam. II Teil: 1 (1889). Division Eumycetes Engler Syllab. ed. 3: 25 (1903). Phylum Carpomyceteae Bessey in Univ. Nebraska Studies 7: 249 (1907). Stamm Mycophyta Pascher in Beih. bot. Centralbl. 48, Abt. 2: 330 ( 1931 ). Kingdom Mycetalia Conard Plants of Iowa iv (1939). Phylum Eumycophyta Tippo in Chron. Bot. 7: 205 (1942). Parasites and saprophytes without flagellate stages, the bodies filamentous, the w;,lls containing no cellulose. This group represents the conventional division or subdivision Fungi of the kingdom of plants, excluding, of course, the bacteria, Oomycetes, chytrids, and Mycetozoa. The name Fungi, used as a scientific name, is properly to be applied, by authority of Linnaeus, to an order. Agaricus campestris L. will be recognized as the standard species of the phylum and of the order. Those who study Inophyta are accustomed to use, for soma and filament respec- tively, the terms mycelium and hypha. The walls of the hyphae are believed to consist of pectic material. A small percentage of chitin is usually present (Schmidt, 1936); cellulose is totally absent (Thomas, 1928; Nabel, 1939; Castle, 1945). The organism Basidiobolus, having hyphae walled with cellulose, is tentatively retained among Inophyta as an exception. The multiplication and dissemination of those organisms is by spores, of various types, scattered in the air. Most Inophyta produce two or more kinds of spores, some of them asexually, others as features of a sexual cycle. Spores produced within cases are called endospores, and the cases sporangia. Other spores are produced externally, commonly by constriction of the ends of hyphae. Spores thus produced are called conidia, and the hyphae or other structures which bear them, conidiophores. Spores are commonly produced not directly on the mycelium but on macroscopic structures of various types, all of which may be called by the familiar term fruit. The common mushroom as we see it is a fruit; it is the temporary spore-producing structure of an organism whose soma consists of filaments living saprophytically in the soil below. It is expedient to mention at this point the growths called lichens, which are traditionally treated as a taxonomic group, either subordinate to Fungi or of the same rank. Lichens are gelatinous or thallose growths, usually of an impure green color, common everywhere, terrestrial or epiphytic, as on stones, trees, or fence posts. The microscope, in the hands of de Bary and others, showed that they consist of cells of two types, colorless filaments like those of Inophyta, and pigmented 120] The Classification of Lower Organisms cells of quite the character of those of certain algae. De Bary (in Hofmeister, 1866) concluded that some lichens are not organisms but combinations of totally diverse organisms. Presently (1868) he was convinced by the work of Schwendener, soon (1868) published under his own name, ". . . dass die Flechten sammt und senders keine selbststiindigen Pflanzen seien, sondern Pilze aus der Abtheilung der Ascomy- ceten, denen die fraglichen Algen — deren Selbststandigkeit ich also nicht bezweifle — ah Nahrpflanzen dienen." In 1879 de Bary coined the term symbiosis to designate the association of different kinds of organisms. In de Bary's usage the term included parasitism; in general usage, it means association to mutual advantage. The lichens are a classic example of symbiosis. Clearly, the group of lichens is not to be maintained; the algal components are known to have natural places among algae, and the inophyte components are to be assigned to their natural places among Inophyta, almost all in various orders of class Ascomycetes. This has already been done by Clements (1909) and Clements and Shear ( 1931 ). The numerous names which students of lichens have given to them are to be applied to the inophyte components. Another common example of symbiosis involving inophytes is furnished by at least some of those which live on or in the tissues of higher plants without killing them (Kelley, 1950). They occur mostly on roots. Frank (1885) coined the term mycorhiza to designate the combination of roots and inophytes; it will be more convenient to hold that this term designates the inophyte component of the combination. Such mycorhizae as cover the growing tips of roots are helpful to their hosts by serving as agents of absorption. Jones (1951) estimated the number of species of Inophyta as 40,000. This is surely an extreme underestimate. Martin (1951) gives reason for believing the num- ber to be about as great as that of flowering plants, of the order of 300,000. The early classifications of "fungi," as by Persoon (1801) and Fries (1821-1832), were based on gross characters. They presented, along with recognizable groups whose names are to be applied in order of priority, others which were mere random assemblages, and whose names are to be abandoned as nomina confusa. De Bary (in Hofmeister, 1866; 1884), having applied comparatively modern methods, established a dozen groups (under German names). These, so far as they are retained in the present phylum, have been assembled as three classes distinguished by details of the sexual cycle. A fourth class, acknowledgedly artificial, is maintained for the accomo- dation of the numerous and important fungi whose sexual cycles are unknown. The termination -mycetes, of the names of the classes and also of various subordinate groups, is the Greek ^uKr]T£q, the plural of (auKT^c;, a mold or mildew. The termi- nation -mycetae which some authors have used is a solecism. 1. Reproducing sexually, or by apomictic pro- cesses clearly of sexual origin. 2. The zygote becoming a thick-walled resting cell; fruits none or inconsiderable Class 1. Zygomycetes. 2. The zygote not becoming a thick-walled resting cell; mostly producing fruits. 3. The zygotes giving rise, usually in- directly, to sporangia called asci, each typically containing eight spores called ascospores Class 2. Ascomycetes. Phylum Inophyta [121 3. The zygotes giving rise indirectly to conidiophores called basidia, each bearing typically four conidia called basidiospores Class 4. Basidiomycetes. 1. Not known to reproduce sexually Class 3. Hyphomycetes. Class 1. ZYGOMYCETES (Sachs ex Bennett and Thistleton-Dyer) Winter Zygomyceten Sachs Lehrb. Bot. ed. 4: 248 (1874). Zygomycetes Bennett and Thistleton-Dyer in Sachs Textb. Bot. English ed. 847 (1875). Class Zygomycetes Winter in Rabenhorst Kryptog.-Fl. Deutschland 1, Abt. 1: 32 (1879). Order Zygomycetes Engler Syllab. 23 (1892). Class Zygomyceteae Schaffner in Ohio Naturalist 9: 449 ( 1909). Inophyta whose zygotes are thick-walled resting cells, in germination giving rise to spores indistinguishable from those produced asexually; hyphae usually without cross- walls; mostly not producing fruits. The standard species is Mucor Mucedo L. Among the Inophyta as here limited, the Zygomycetes appear to be primitive (an alternative hypothesis, that certain Ascomycetes are primitive, will be discussed be- low). Traditionally, the Zygomycetes are associated with the Oomycetes. The asso- ciation is probably mistaken, being based merely on similarity of body form: the Zygomycetes are terrestrial instead of aquatic, produce no flagellate cells, have no cellulose in their cell walls (except in Basidiobolus) , and do not produce female gametes by the cutting out of cells within a cell. In later editions of Engler's Syllabus (1924), one finds most of the chytrids included among the Zygomycetes, instead of in their conventional place among the Oomycetes. The hypothesis thus suggested, that the Opisthokonta may represent the ancestry of the Inophyta, is attractive, but not to present knowledge supported by convincing evidence. Class Zygomycetes and phylum Inophyta must as yet be regarded as of unknown origin and treated as isolated. There are some 500 known species of Zygomycetes. They form two orders. The bulk of the group, and the typical examples, are order Mucorina. A minority, distinguished by parasitism and by explosively discharged conidia, are order Entomophthorinea. Order 1. Mucorina [Mucorini] Fries Syst. Myc. 3: 296 (1832). Suborder Mucorineae Engler in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. 1: iv (1897). Order Mucorineae Campbell Univ. Textb. Bot. 158 (1902). Order Spirogyrales (presumably in part only) Clements Gen. Fung. 12 (1909). Order Mucorales Smith Crypt. Bot. 1 : 405 (1938). Order Zoopagales Bessey Morph. and Tax. Fungi 117 (1950). The typical Zygomycetes, mostly saprophytic, not producing explosively dis- charged conidia [Piloholus produces explosively discharged sporangia). The asexual reproductive structures of the supposedly primitive Mucorina, as Mucor and Rhizopus, are solitary globular sporangia terminal on erect hyphae. In the developing sporangium, a dome-shaped basal sterile area, the columella, is set apart by cleavage followed by deposition of a wall. The protoplasm above the 122] 'I'hc Classification of Lower Organisms Fig. 24. — Zygomycetes: a-d, Rhizopus nigricans; a, sporangia x 50; b-d, prega- mctes, suspensors and gametes, and zygote x 200. e. Zygote of Phycomyccs nitens after Blakeslcc ( 1904). f, g, Conidiophore with young conidia, and mature conidia, of Syncephalis pycnosperma after Thaxtcr (1897). h, i, Conjugation of Synce- phalis nodosa after Thaxter, op. cit. j, Sporangium of Synccphalastrum raccmosum after Thaxter, op. cit. k, Sporangium of Flaplospoiangium lignicola after Martin (1937), x 1,000. Phylum Inophyta [ 123 columella undergoes cleavage to form spores, which may remain plurinucleate (Swingle, 1903). Other members of the order exhibit transitions (apparently two distinct series of transitions) from sporangia as just described to typical conidia. Syngamy occurs when the tips of pairs of hyphae meet and are cut off by crosswalls to act as multinucleate gametes. The process is regarded as conjugation, although the gametes of a pair are usually not of the same size. Conjugation does not occur at random, but, in most Zygomycetes, between branches from hyphae of two mating types, designated plus and minus (the distinction of mating types is not identical with the differentiation of sexes). Zygomycetes were the first group reproducing by conjugation in which a distinction of mating types was discovered; the discovery was by Blakeslee (1904). Syngamy is preceded by a flare of mitoses in the gametes. The mitotic figures are sharp-pointed, as though centrosomes were present; the haploid chromosome number appears to be 2. The process is not meiotic (Moreau, 1913). After these divisions, the walls between the gametes break down and the nuclei unite in pairs. Unpaired nuclei, presumably contributed in excess by one gamete or the other, undergo disso- lution (Keene, 1914, 1919). Ordinarily, the zygote enlarges and becomes a thick- walled resting spore; in some examples, the resting spore forms as an outgrowth on what was one of the gametes. In Phycomyces, Absidia, and Syncephalis, the hyphae which have produced the gametes, and to which the zygote remains attached, .send out branches which form a layer about the zygote. These branches might be inter- preted as making up fruits. Endogone produces definite fruits of considerable size. A zygote germinates by production of a hypha bearing a sporangium (Blakeslee, 1906). Meiosis is believed to occur in the course of germination. While Mucorina in general are saprophytic, some of them are parasitic on others, Piptocephalis and Chaetocladhim on Mucor, and Parasitella on Absidia. Drechsler (1935, 1937) discovered a number of organisms apparently of this group parasitizing amoebas and nematodes in the soil. The Mucorina may be treated as five families. 1. Not producing macroscopic fruits. 2. Not parasitic on amoebas or nematodes. 3. All spores produced in sporangia with columellae Family 1. Mucoracea. 3. Not as above. 4. Producing sporangia or else conidia as outgrowths from a knob, homologous with a sporangium, solitary on an un- branched stalk Family 2. Piptocephalidacea. 4. Sporangia or conidia solitary and terminal on branches of a branched sporangiophore or conidiophore; sporangia, if produced, without columellae Family 3. Mortierellacea. 2. Parasitic on amoebas or nematodes Family 4. Zoopagacea. 1. Producing macroscopic fruits Family 5. Endogonacea. Family 1. Mucoracea [Mucoraceae] Cohn in Hedwigia 11: 17 (1872). Mucorina whose spores are produced exclusively in sporangia with columellae solitary on un- branched sporangiophores. Mucor L., typified by M. Mucedo, is now limited to a 124] The Classification of Lower Organisms small group mostly saprophytic on manure. Pilobolus, another coprophilous genus, is distinguished by sporangiophores which become swollen at the summit, bend toward the light, and discharge the sporangia violently to a distance of several meters. Rhizopus nigricans, the common black bread mold; Phycomyces, Ahsidia, Sporodinia, Zygorhynchus. Family 2. Piptocephalidacea [Piptocephalidaceae] Schroter in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. 1: 132 (1893). Family Choanephoraceae Schroter op. cit. 131. Mucorina producing sporangia without columellae, or conidia, in compact clusters terminal on unbranched stalks. Blakesleea, transitional between the preceding family and this, may produce solitary sporangia with columellae, or else, as out- growths from the primordia of sporangia, clusters of minuscule sporangia without columellae. Cunninghamella, producing heads of globular conidia; Syncephalastrum, with clustered cylindrical sporangia; Syncephalis and Piptocephalis, producuig clustered chains of conidia. Family 3. Mortierellacea [Mortierellaceae] Schroter op. cit. 130. Family Chaeto- cladiaceae Schroter op. cit. 131. Mucorina whose sporangiophores or conidiophores are branched, the sporangia (without columellae) or conidia solitary and terminal on the branches. Thamnidium, Chaetocladium, Mortierclla, Haplosporangium. Family 4. Zoopagacea [Zoopagaceae] Drechsler in Mycologia 27: 37 (1935). Mu- corina parasitic in amoebas or nematodes, producing conidia. The hosts of Zoopaga- cea inhabit the soil and are infected by contact with hyphae or conidia. From the point of contact, a hypha grows into the host and gives rise to a mycelium; this is in some examples reduced to a single coiled cell. The host being killed, the parasite sends out hyphae which may produce conidia, usually in chains, or else may conjugate and produce zygotes. Endocochlus, Cochlonema, Bdellospora, Zoopage, Acaulopage, Stylopage. Family 5. Endogonacea [Endogonaceae] Paoletti in Saccardo Sylloge Fungorum 8: 905 (1889). Endogonei Fries. Mucorina saprophytic in soil or wood, producing macroscopic subterranean fruits. The fruits may reach a diameter of 2 cm. Within them, the tips of hyphae are cut off by crosswalls, and develop either into sporangia without columellae or into gametes. Order 2. Entomophthorinea [Entomophthorineae] (Engler) Campbell Univ. Textb. Bot 161 (1902). Suborder Entomophthorineae Engler in Engler and Prantl Nat. Pflanzen- fam. I Teil, Abt. 1: iv (1897). Order Entomophthorales Smith Crypt. Bot. 1: 408 (1938). Zygomycetes, mostly parasitic, producing explosively discharged conidia [Masso- spora, while clearly belonging to the group, is an exception to the stated character). These organisms, although of the general nature of ordinary Inophyta, exhibit cytological characters markedly distinguishing the two families from the generality of Inophyta and from each other. The position here given to them is the customary one; it is doubtful that it is natural. Family 1. Entomophthoracea [Entomophthoraceac] Berlese and de Toni in Sac- cardo Sylloge 7: 280 (1888). Most species are parasitic in the bodies of insects, whose tissues they replace. The hyphae become divided by crosswalls, and the multi- nucleate cells thus produced tend to round up and become separate. A well-nourished cell may send forth a hypha which reaches the outer air and whose tip is cut off and discharged in the direction of the light. Martin (1925) and Couch (1939) described Phylum Inophyta [ 125 the mechanism of discharge. The conidiophore ends in a columella projecting into the base of the conidium. The columella develops a double wall. Increasing pressure within the conidium causes a sudden eversion of the wall on the side of the conidium, and this movement throws the conidium forth to a distance of perhaps 1 mm. Coni- dia which come down on unfavorable substrata may form and discharge secondary conidia. Adjacent cells may conjugate, the thick-walled zygote forming either in one of them or as an outgrowth from one of them. Many examples produce thick-walled resting spores without conjugation. Olive (1906) described the nuclei and the process of mitosis in Empusa. The resting nuclei are fairly large, 7-9 [I in diameter. In the course of division, two stain- resistant granules are seen, with strands of chromatin radiating from them. These move apart, while the nucleus becomes dumb-bell shaped. The nuclear membrane remains intact and division is completed by its constriction. As Olive remarked, the process is much as in Euglena. Entomophthora, Empusa, and Massospora attack insects; the first produces zygotes, while the other two produce asexual resting spores; Massospora does not discharge the conidia violently. Conidiobolus and Delacroixia are saprophytic. Completoria attacks the prothallia of ferns. Ancylistes, a parasite in the green alga Closterium, was formerly included among chytrids or Oomycetes. Berdan (1938) showed that it belongs here; it produces conidia and zygotes quite of the character of the present group, and does not produce zoospores. Family 2. Basidiobolacea [Basidiobolaceae] Engler and Gilg Syllab. ed. 9 u. 10: 45 (1924). Basidiobolus ranarum Eidam (1886) occurs in the intestinal contents of frogs and toads as uninucleate cells, solitary or in brief filaments, walled with cellu- lose. In manure the filaments develop into a scant branching mycelium. The proto- plasm gathers in the ends of erect hyphae which are cut off as conidia and discharged. Conjugation occurs between adjacent cells of a filament. It is preceded by a single nuclear division in each gamete (Fairchild, 1897). In this process, the nuclear mem- brane disappears and the numerous minute chromosomes are found in a blunt-ended spindle without centrosomes. Each gamete form a papilla; one of the two nuclei enters the papilla, whose contents, after being cut oft by a wall, die and disappear. The gametes and their nuclei unite and the zygote secretes a thick wall. Class 2. ASCOMYCETES (Sachs ex Bennett and Thistleton-Dyer) Winter Order .4jco5porgag Cohn in Hedwigia 11: 17 (1872). Ascomyceten Sachs Lehrb. Bot. ed. 4: 249 (1874). AscoMYCETES Bennett and Thistleton-Dyer in Sachs Textb. Bot. English ed. 847 (1875). Class AscoMYCETES Winter in Rabenhorst Kryptog.-Fl. Deutschland 1, Abt. 1 : 32 (1879). Class Ascosporeae Bessey in Univ. Nebraska Studies 7: 295 (1907). Class Ascomycetae Schaffner in Ohio Naturalist 9: 449 (1909). Inophyta which produce, as a feature of the sexual cycle, sporangia called asci, in which the spores, called ascospores, typically eight in number, are delimited by the manner of cell division called free cell formation, i.e., in such fashion as to exclude a part of the cytoplasm. 126] The Classification of Lower Organisms The hyphae of Ascomycetes are septate and the cells most often uninucleate. Most Ascomycetes produce, beside the ascospores, conidia of one type or another. A mycelium may produce a mass of densely woven hyphae with conidia on the sur- face; such a mass is called an acervulus or sporodochium. Either a mycelium or an acervulus or sporodochium may send up spore-bearing columns called coremia. Many Ascomycetes produce, either directly from the mycelium or from special structures consisting of interwoven hyphae, globular or flask-shaped structures which produce conidia internally and release them through a pore. These structures are called pycnidia, and the spores pycniospores. In many examples, the pycniospores are capable of functioning as sperms; so far as this is true, the pycnidia may alter- natively be called spermagonia, and the pycniospores spermatia. Hyphae woven into a mass may go into a resting condition, becoming thick-walled, hard, and usually dark in color. The resulting structure is a sclerotium. If a structure of the general nature of an acervulus, sporodochium, or sclerotium gives rise either to pycnidia or to fruits bearing asci, it is called a stroma. As to asci and ascospores, Dangeard (1893, 1894, 1907) reached definitely the conclusion that they are essentially sexual products. There had been earlier observa- tions, beginning with de Bary, 1863, that there are meetings, coilings together, and fusions of hyphae as a preliminary to the production of asci. Many ascomycetes are of two mating types; this was first discovered of Glomerella, by Edgerton (1914). As Dodge (1939) remarks, the mating types are not sexes; in forms producing recogniz- able male and female reproductive structures, each mating type may produce both. In Ascomycetes which may be regarded as primitive, difTerentiated male and fe- male cells are produced. The male cell or antheridium is ordinarily terminal on a hypha. The female cell (constituting, together with other differentiated cells of the same hypha, if any are present, the ascogonium) may be terminal; more often it bears an elongate cell, or a chain of cells, called the trichogyne, and having the function of reaching the antheridium. In some Ascomycetes, antheridia are produced, but syn- gamy does not take place; the egg is binucleate or multinucleate, and the nuclei within it take the part of gamete nuclei in further development. There are others in which no antheridia are produced. Hansen and Snyder (1943) found, in Hypornyces Solani var. Cucurbitae, that "any part of the living thallus, ascospores, conidia or bits of the mycelium could act as the male fertilizing agent." There are forms in which fusions take place between undifferentiated hyphal cells; and yet others in which it appears that the paired nuclei involved in sexual processes arise by divisions of a single nucleus originally present in a spore. In some Ascomycetes, syngamy is followed immediately by karyogamy, and the zygote develops directly into a single ascus. In the overwhelming majority of the group, asci are produced indirectly, and there is no fusion of nuclei until this takes place. The zygote sends out hyphae called ascogenous hyphae, recognizably different from the vegetative ones. The cells of the ascogenous hyphae arc binucleate; or, arising from a multinucleate zygote, become binucleate by the establishment of crosswalls. The two nuclei of each cell divide concurrently and the cell walls are so placed that each cell receives nuclei of different origin. This effect is achieved in the final cell division before ascus formation by a peculiar process called crozier forma- tion. The terminal cell of the ascogenous hypha becomes bent to the form of a hook; the nuclei divide concurrently, and cell walls appear between the daughter nuclei of each pair; the middle cell of the row of three thus produced remains binucleate and becomes an ascus. The uninucleate terminal and basal cells lie side by side, and may Phylum Inophyta [127 fuse to form a binucleate cell which may become an additional ascus, or else may grow forth and give rise to more asci than one. The stage consisting of cells with two nuclei of different origin is called the dikaryophase. It is characteristic of Ascomycetes ,and also of Basdiomycetes: among Inophyta, it is a normal and familiar thing. To a concept of cytology founded on studies overlooking the Inophyta, it would appear an extreme anomaly, almost an impossibility. It has the appearance of a rather awkward device for making cells genetically and physiologically diploid while the nuclei remain haploid. In most Ascomycetes it is a brief stage, but there are some, as Taphrina, whose mycelium consists prevalently of binucleate cells. The detailed behavior of nuclei in the ascus was first described by Harper (1895, 1897, 1900) from studies of Peziza, Sphacrotheca, Erysiphe, and Pyronema. The two nuclei in the primordium of the ascus unite into one. The fusion nucleus divides three tim.es, each time in much the same manner. A centrosome with astral rays is present at the nuclear membrane, apparently outside. It divides, and a spindle forms, inside the intact nuclear membrane, between the daughter centrosomes. The chromo- somes appear and divide. As they move toward the poles of the spindle, the nuclear membrane collapses or dissolves, leaving the spindle free in the cytoplasm. The mass of chromatin at each pole of the spindle shreds out into a nuclear network, duly surrounded by a nuclear membrane and usually containing a nucleolus. Haploid chromosome numbers of Ascomycetes (all of which have been observed in the ascus) include the following: Ascoidea rubescens, fide Walker (1935) 2 Eremascus alhus, fide De Lamater et al. (1953) 6 G/om^r(?//ro\vn {\9\b) 5 Taphrina deformans, fide Martin (1940) 4 According to Harper, when the third division in the ascus is complete, each of the eight nuclei produced by it thrusts forths its centrosome upon a beak. The astral rays of the centrosomes become recurved in the cytoplasm about the nucleus, and grow and multiply until they are converted into a smooth membrane, outside of which a wall is deposited. Most observers have not seen so much detail. Brown (1911) and Dodge (1937) describe the cell membrane of the ascus, apparently under the influence of the centrosome of each nucleus, as cutting into the cytoplasm in an ellip- soid pattern. In Taphrina (Martin, 1940), the cytoplasm of the spores is delimited simply by accumulation about the nuclei. By whatever process the ascospores are cut out. some of the cytoplasm of the ascus is excluded and left without nuclei. Harper (1899) proposed to limit the older term free cell formation to processes which have this effect; he observed that the occurrence of such processes distinguishes asci from the sporangia of Oomycetes and Zygomycetes, in which spores are cut out by cleavage. Harper believed that a fusion of nuclei follows immediately the fusion of gametes; that the karyogamy observed in the ascus is a uniting of diploid nuclei, producing tetraploid nuclei; and that the characteristic three nuclear divisions in the ascus are necessary for reduction of the chromosome number from tetraploid to haploid. These 128] The Classification of Lower Organisms hypotheses, long accepted as possible, were disproved by genetic studies by Betts and Meyer (1939) and Keitt and Langford (1941). In the asci of many species, the spores lie in a single series in which their order is determined by the divisions which produce their nuclei. By refined technique, the spores from a single ascus may be identified, separated, and cultivated. It is then observed that the mycelia grown from the first four spores may differ in some particular character from those grown from the second four spores; those from the first pair of spores may differ from those from the second; but those from two members of any of the pairs, first, second, third or fourth, are always alike. These observations mean that the first two divisions in the ascus constitute the meiotic process, the third being mitotic. Lucas (1946) obtained cytological evidence refined enough to confirm this conclusion. Asci are almost always produced in fruits, which may be called ascocarps. The ascocarp aside from the asci arises usually from vegetative hyphae; in the Ascomy- cetes regarded as primitive, it does not begin to develop until after fertilization, but in the higher ones it may develop in advance of fertilization and become the seat of this process. There are several types of ascocarps, among which three are most familiar. A small ascocarp completely enclosing the asci is a cleistothecium. Cleistothecia were formerly included under the term perithecium; that term will better be limited to small fruits which are globular or vase-like, opening through a single pore, the ostiole, and differing from the pycnidia already described in producing ascospores instead of conidia. A fruit in which the asci form a broad layer which is typically fully exposed at maturity, the whole being ordinarily of the form of a disk or cup, larger than a cleistothecium or perithecium, is an apothecium. Asci produced in perithecia or apothecia usually discharge the ascospores vio- lently. The mechanism of discharge is apparently simply turgidity. Some asci show no visible adaptations for the discharge of spores; others have lids (opercula) whose position determines the direction of discharge. Certain large apothecia can throw the spores to a distance of 10-20 cm.; the discharge is so governed by tempera- ture and humidity as to occur in gently moving rather than in still air. By blowing across these apothecia one can make them throw out a visible cloud of spores. Heald and Walton (1914) reviewed many older observations of violent discharge by perithecia, the oldest by Pringsheim on Sphaeria Scirpi, 1858. Rankin, 1913, found that each ascus in turn breaks loose, comes up to the ostiole, projects through it, throws out its spores, and collapses to make room for another. Weimer (1920) found that the perithecia of Pleurage curvicolla bend toward the light and throw the spores to a maximum distance of 45 cm., which is apparently the record. There is a widely entertained hypothesis that the Ascomycetes evolved from the red algae. It appears to have developed from a piece of classification by Sachs (1874), who proposed a class Carposporeen, to consist of the red algae, certain higher green algae, and the Ascomycetes and Basidiomycetes. A number of resemblances support it. Both red algae and Ascomycetes include many parasites; both lack flagellate cells; both have differentiated gametes, the egg bearing a trichogyne; in both, fertilization leads to further development before spores are produced. In addition to these genuine resemblances, an imaginary one was influential, namely the double fertilization ascribed to the red algae by Schmitz and to the Ascomycetes by Harper. Numerous as these resemblances are, they are not now believed to indicate relationship. Atkinson (1915) formulated the counter-argument. The Ascomycetes resemble the Mucorina in nutrition, in producing no flagellate cells, and in multi- Phylum Inophyta [ 129 nucleate gametes. The germination of the zygote of the Mucorina, by the production of a hypha bearing a sporangium, resembles the production of ascogenous hyphae by the zygotes of Ascomycetes. Two principal changes would convert Mucorina into Ascomycetes: the zygote should cease to be a resting spore, and cell division within the sporangium should be by free cell formation. This could happen if the centro- somes of the ultimate nuclei of the sporangia were in control of cleavage, and if these nuclei were so far separated that considerable areas of cell membrane would lie beyond the influence of the centrosomes, with the effect that the cell membrane, furrowing in to delimit a spore around each nucleus, would leave some of the cyto- plasm outside of all of the spores. The organisms listed below as the first order of Ascomycetes, Endomycetalea, are but poorly known, yet seem genuinely to represent the transition from Mucorina to typical Ascomycetes. It is not yet possible to formulate a system of orders of Ascomycetes with the expectation that it will not be found to require much amendment^. The following will serve tentatively; excellent contemporary authority makes several orders each of the ones listed fourth, fifth, and seventh. l.Ascus developed directly from the zygote (or apomictically from an unfertilized cell); not producing fruits Order 1. Endomycetalea. l.The zygote giving rise to filaments of cells with more than one nucleus, these producing the asci. 2. Producing fruits. 3. The fruits cleistothecia. 4. Asci scattered in the fruits; mostly saprophytes with branched conidiophores Order 2. Mucedines. 4. Asci in one cluster, or solitary, in the fruits; mostly parasites with unbranched conidiophores Order 3. Perisporiacea. 3. The fruits, originally closed, open- ing by irregular pores or regular or irregular clefts Order 4. Phacidialea. 3. The fruits apothecia Order 5. Cupulata. 3. The fruits perithecia. 4. Producing a normal mycelium Order 7. Sclerocarpa. 4. Parasitic on insects, the mycel- ium reduced Order 8. Laboulbenialea. 2. Not producing fruits, the asci arising di- rectly from the mycelium Order 6. Exoascalea. Order 1. Endomycetalea [Endomycetales] Gaumann Vergl. Morph. Pilze 135 (1926). Subclass Hemiasci Engler Syllab. 26 (1892). ILuttrell (1951) has presented a complete reorganization of the class. He sets apart as a major subordinate group Bitunicatae five orders in which the ripe ascus exudes 3 vesicle and discharges the spores from this. 130 ] The Classification of Lower Organisms Subclass Hemiasci or Hemiasceae, with suborder (Unterreihe) Hemiascineae, and suborder Protoascineae of subclass Euasci, Engler in Engler and Prantl Nat. Pflanzelfam. I Teil, Abt. 1 : iv (1897), the names not based on those of genera. Order Protoascineae Campbell Univ. Textb. Bot. 165 (1902). Order Hemiascalcs Engler Syllab. ed. 3: 28 (1903). Ascomycetes whose asci develop directly from the zygotes. Two families may be recognized. Family 1. Endomycetacea [Endomycetaceae] Schroter in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. 1: 154 (1894). Family Ascoideaceae Schroter op. cit. 145. Mostly saprophytes, the uninucleate or multinucleate cells of the filaments tending to round up, become separate, and function as conidia; the zygotes, produced by syngamy of scarcely differentiated cells, enlarging and becoming asci of 4, 8, or many spores cut out by free cell formation. Dipodascus, Eremascus, Endomyces, Ascoidea. The asci of the last are apparently produced asexually (Walker, 1935). The genus Protomyces requires mention. It is a parasite on higher plants, producing walled resting spores which germinate by producing a sporangium of many spores. It is chytrid-like, but its spores are non-motile. Its proper place in classification has for a long time been a puzzle. Family 2. Saccharomycetacea [Saccharomycetaceae] (Rees) Schroter op. cit. 153. CXa^?, znd iarm\y Saccharomycetes y assemble about the centrosomes. Mitosis is completed by constriction of the nuclear membrane. The blepharoplast divides at the same time as the nucleus. The flagellum splits to a short distance and one of the branches breaks loose; one daughter blepharoplast retains essentially the whole of the original flagellum while the other generates one which is almost entirely new. The parabasal body undergoes constriction. The cell membrane cuts in in such fashion as to divide the cell longitudinally. The blepharo- plast and the parabasal body persist through the non-flagellate leishmania stage. Reports that the nucleus may generate these structures, or that one of them may generate another, were apparently mistaken. Schaudinn described complicated processes by which a trypanosome generates differentiated male and female gametes which duly undergo syngamy. His account is believed to have resulted from mistaking stages of a sporozoan for those of a trypa- nosome. Still, the occurrence of syngamy among trypanosomes is inherently probable. Phylum Protoplasta [ 163 Family 4. Cliaetoproteida [Chaetoproteidae] Poche in Arch. Prot. 30: 172 (1913). Family Rhizomastigina Biitschli in Bronn Kl. u. Ord. Thierreichs 1: 810 (1884). Family Rhizomastigaceae Senn in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. la: 113 (1900). Family Mastigamoebidae Kudo Protozoology ed. 3: 263 (1946). Amoeboid organisms bearing one anterior flagellum, either permanently or tempor- arily. In polluted soil or water, or commensal or pathogenic in animals. The oldest genus, Chaetoproteus Stein {Mastigamoeba F. E. Schulze, 1875; Din- amoeba Leidy ?) remains poorly known. This organism and Mastigella are described as fairly large; Craigia is much smaller. Rhizomastix is doubtfully distinct from Craigia. Early names of this family appear to refer to Rhizomastix as the type, but the family is much older than the genus, and the names are not valid. Order 2. Polymastigida Calkins Biol. Prot. 292 (1926). Family Polymastigina Biitschli in Bronn Kl. u. Ord. Thierreichs 1: 842 (1884). Order Polymastigina Blochmann Mikr. Tierwelt ed. 2, 1: 47 (1895). Subclass Distomatineae Engler in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. la: iv (1900). Order Distomatinales Engler Syllab. ed. 3: 7 (1903), not based on a generic name. Orders Pyrsonymphina, Oxymonadina, Retortomonadina, and Distomata Grasse Traite Zool. 1: fasc. 1: 788, 801, 824, 963 (1952). Non-pigmented flagellates with simple or acroneme flagella of definite number, from four to eight (two in Retortomonas), in the individual neuromotor system, and accordingly on the individual cell, except when the neuromotor systems are multi- plied; not of the definite characters of the following order. Free-living, chiefly in foul waters, or commensal or parasitic in animals. Polymastix is presumably the type of the group. It was listed with a query in Biitschli's original publication of family Polymastigina. In the generality of Polymastigida, the cells are dorsiventral and have single nuclei and neuromotor systems. There are derived examples in which the cells are spirally twisted. There is a group in which the cells are double, having two nuclei and neuro- motor systems. In another group there are two or more neuromotor systems, usually with more than one nucleus; the cells consist of units in a whorled or spiral arrange- ment, so that as wholes they are of radial symmetry. The neuromotor system consists primarily of ( 1 ) the flagella; (2) one or more blepharoplasts from which the flagella spring; (3) one or more rhizoplasts linking together the parts of the system; and (4) a centrosome located just outside the nuclear membrane. Furthermore, (5) a parabasal body may be present. (6) An axostyle is a rod imbedded in the cytoplasm. In Hexamita the axostyles are the proximal ends of backwardly directed flagella; axostyles occurring in various other genera of the order appear also to be homologous with flagella. Nuclear and cell division have been observed in various genera, as in Hexamita by Swezy (1915); in Streblomastix by Kidder (1929); in Giardia by Kofoid and Chris- tianson (1915) and Kofoid and Swezy (1922); and in O.V);mona^ by Connell (1930). Cleveland (1947) observed in Saccinobaculus a multiplication of nuclei followed by their fusion in pairs, and by meiosis in the fusion nuclei: thus there is a .sexual cycle without fusion of cells. It is not probable that sexual reproduction does not occur in the generality of the group, but it has not been observed in any others. 164] The Classification of Lower Organisms Fig. 31. — PoLYMASTAcroA : a, Polymastix Mclolonthae after Swezy (1916). b, Streblomastix Strix x 1,000 after Kidder ( 1929) . c, d, Giardia cnterica after Kofoid & Swezy (1922). Trichomonadina: e, Hcxamastix Tcrmopsidis after Kirby (1930). i' Tricercomitus Termopsidis 2ihtv YJirhy (1930). g, Macrotrichomonas pulchra after Kirby (1938). h. Trichomonas tenax x 4,000 after Hinshaw (1926). i, Pentatrichomonas obliqua after Kirby (1943). j, Snydcrella Tabogae x 500 after Kirby ( 1929) . x 2,000 except as noted. Phylum Protoplasta [165 In making the clearly natural group of trichomonads a separate order, Kirby ( 1947 ) removed the majority of the species formerly assigned to this order, and left a mis- cellany of small isolated families. It seems not expedient to make them several small orders, as Grasse has done; rather they are to be held together until their respective relationships become evident. A hint of Hall has led in the present work to the trans- fer of family Trimastigida to order Ochromonadalea. 1. With a single nucleus and neuromotor system. 2. Cells not spirally twisted, at least not as wholes and not conspicuously Family 1. TEXRAMiTroA. 2. Entire cells conspicuously spirally twisted. 3. With four free flagella Family 2. Streblomastigida. 3. With four or eight flagella whose proximal ends are grown fast to the cell membrane Family 3. Dinenymphida. 1. With one or several nuclei and two or more neuromotor systems Family 4. Oxymonadida. 1. With two nuclei and neuromotor systems Family 5. Trepomonadida. Family 1. Tetramitida [Tetramitidae] Kent Man. Inf. 1: 312 (1880). Families Tetramitina and Polymastigina Biitschli in Bronn Kl. u. Ord. Thierreichs 1: 841, 842 (1884). Family Tetramitaceae Senn in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. la: 143 ( 1900) . Family Polymastigidae Doflein Protozoen 83 ( 1901 ) . Fam- ily Chilomastigidae Wenyon (1926). Family Costiidae Kudo Handb. Prot. 153 (1931). Family Retortomonadidae Wenrich 1932. Cells mostly dorsiventral and with four flagella; these uniform or differentiated; when differentiated, one or two may trail behind the cell. Axostyles present or absent, parabasal bodies not reported. Like the order, the family is a miscellany; good authority has made as many as four families of the few genera. Tetramitus, free-living, unfamiliar. Costia, occurring usually as sessile parasites on fishes. Polymastix, in insects. Monocercomonoides, in insects and vertebrates. Chilomastix, in insects and vertebrates, cells marked by a cytostomal groove into which one of the flagella, shorter than the others, is recurved. The species which occurs in man (usually, as it appears, as a harmless commensal) is in most works called C. Mesnili; the correct name is apparently Chilomastix Hom- inis (Davaine) n. combl. Current authority places next to Chilomonas the biflagellate Retortomonas, also in insects and vertebrates, and having cells of essentially the same structure. ^Kofoid (1920) gave the history involved in this combination. Davaine, 1860, de- scribed the flagellates Cercomonas Hominis var. A and var. B. The two forms are not of the same species, and Moquin-Tandon, in the same year, re-named them respectively C. Davainei and C. obliqua. They are not of the same genus, being re- spectively a Chilomastix and a Pentatrichomonas, under which genera they have various names. Kofoid named them respectively Chilomastix davainei and Tricho- monas hominis. In so doing, he may be held to have exercised his right to choose a type in a group in which no type has been designated; but it is arguable on the con- trary that an author who designates a var. A designates the type in doing so. It is on the basis of this argument that the new combination here published is applied to the Cercomonas Hominis var. A of Davaine. 166] The Classification of Lower Organisms Family 2. Streblomastigida [Streblomastigidae] Kofoid and Swezy in Univ. Cali- fornia Publ. Zool. 20: 15 (1919). The only known species is Strehlornastix Strix, a slender spirally twisted organism with four anterior flagella, free-swimming or at- tached in the gut of the termite Termopsis. The significance of the epithet Strix (a Greek noun meaning screech owl) as applied to this species is not clear. Family 3. Dinenymphida [Dinenymphidae] Grassi in Atti Accad. Lincei ser. 5. Rendiconti CI. Sci. 20, 1° Semestre: 730 (1911). Elongate flagellates, the four or eight anterior flagella adherent to the body and spirally twisted with it, free at their distal ends. Often beset with spirochaets, which have been mistaken for additional flagella; the family has been misplaced in order Hypermastigina. Dinenympha and Pyrsonympha in termites; Saccinohaculus in the wood roach Cryptocercus. Family 4. Oxymonadida [Oxymonadidae] Kirby in Quart Jour. Micr. Sci. n. s. 72: 380 ( 1928) . Flagellates with radially symmetrical bodies including two or more neuro- motor systems, entozoic in termites of subfamily Kalotermitinae. Each pear-shaped cell of Oxymonas has one nucleus and two neuromotor systems (Kofoid and Swezy, 1926). In Microrhopalodina {Proboscoidella) each cell contains a whorl of nuclei, each with its separate neuromotor system (Kofoid and Swezy, 1926; Kirby, 1928). These organisms are superficially closely similar to the Calonymphida, from which Kirby distinguished them. Family 5. Trepomonadida [Trepomonadidae] Kent Man. Inf. 1: 300 (1880). Family Hexamitidae Kent op. cit. 318. Distomata Klebs in Zeit. wiss. Zool. 55: 329 (1893). Family Distomataccae Senn in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. la: 148 (1900). Flagellates each with two nuclei and two neuromotor systems. In most examples, each half-cell is dorsiventral, and the whole isobilateral, with two cytostomes. Most of the genera, Trepomonas, Gyromonas, Trigonomonas, are free- living in fresh or foul waters and have been little studied. Hexamita occurs both free- living and entozoic, in roaches and in all classes of vertebrates; the cells have eight flagella {Octomitus Prowazek and Urophagus Moroff are synonyms). In Giardia the half-cells are asymmetric, and the whole cells dorsiventral, with one cytostome. There are several species, serious pathogens in mammals. The valid name of the species in man, usually known as G. Lamblia, appears to be G. enterica (Grassi) Kofoid (1920). Order 3. Trichomonadina Grasse Traite Zool. 1, fasc. 1: 704 (1952). Order Trichomonadida Kirby in Jour. Parasitol. 33: 215, 224 (1947), preoc- cupied by family TRiCHOMONADroAE Wenyon (1926). Flagellates of the general nature of the Polymastigida having in each neuromotor system one trailing flagellum; axostyle present, rigid, apparently not homologous with the flagella; parabasal body present, disappearing during mitosis. Entozoic, the majority of the species, to the number of fully 150, occurring in termites. The base of the trailing flagellum may be underlain by a cresta, a more or less prominent body distinct both from parabasal body and from axostyle. The trailing flagellum may be grown fast to the cell membrane and converted into an undulating membrane; in this case it is underlain by a rod called the costa, apparently homolo- gous with the cresta (Kirby, 1931). Nuclear and cell division have been described in Trichomonas by Kuczynski (1914), Kofoid and Swezy (1915, 1919; the Trichomitiis described in the latter year is a Trichomonas) and Hinshaw (1926). The centrosome (or a combined cen- trosome and blcpharoplast, the centroblcpharoplast of Kofoid and Swezy, 1919) lies Phylum Protoplasta [167 outside the nuclear membrane. This structure divides and the daughter structures move apart along the nuclear membrane. They remain connected, usually until mito- sis is complete, by a stainable strand, the paradesmose. Definite chromosomes, usually few in number, and an intranuclear spindle, are formed. Mitosis is completed by con- striction of the nuclear membrane. In what appears to be the typical course of cell division, the rhizoplast and blepharoplast divide when the centrosome does. Of other parts of the neuromotor system, some may remain connected to one blepharoplast and some to the other; some may disappear. The parts needed to complete a neuro- motor system are regenerated in each daughter cell. 1. With a single nucleus and neuromotor system. 2. Lacking a cresta, costa, or undulating membrane Family 1. MoNOCERCOMONADroA. 2. With a trailing flagellum whose base is underlain by a cresta Family 2. DEVEScoviNroA. 2. With a trailing flagellum grown fast to the cell membrane, forming an undula- ting membrane underlain by a costa Family 3. Trichomonadida. 1. With several nuclei and neuromotor systems. . Family 4. CALONYMPHroA. Family 1. Monocercomonadida [Monocercomonadidae] Kirby in Jour. Parasitol. 33: 225 (1947). Minute flagellates of the appearance of certain Tetramitida, but having a firm axostyle, the parabasal body disappearing and a paradesmose forming between the daughter centrosomes during mitosis; lacking a cresta, costa, or undulat- ing membrane; entozoic in termites and other insects, and in all classes of vertebrates. Monocercomonas, Hexamastix, Tricercomitus. Family 2. Devescovinida [Devescovinidae] Doflein Lehrb. Prot. ed. 3: 537 (1911). Subfamily Devescovininae Kirby in Univ. California Publ. Zool. 36: 215 (1931). Organisms with three anterior flagella and a larger trailing flagellum underlain by a cresta; confined to termites of the families Mastotermitidae, Hodotermitidae, and Kalotermitidae, being most abundant in the last. The cells, usually fairly large, ingest scraps of wood and are presumed to contribute to the lives of their hosts by digesting it. Devescovina, Gigantomonas, Macrotrichomonas, Foaina, Parajoenia, Metadeves- covina. Spirochaets which share the habitat of these organisms are commonly found adhering to their cell membranes, and were mistaken for additional flagella in the original descriptions of some of the genera. Family 3. Trichomonadida [Trichomonadidae] Wenyon Protozoology 1 : 646 (1926). Flagellates with three or more flagella directed forward and one trailing, the proximal part of the latter grown fast to the cell membrane and forming an undula- ting membrane underlain by a costa. Entozoic in a wide variety of animals. Tricho- monas, normally with four anterior flagella, is the most numerous genus. It occurs in termites, including those of the advanced family Termitidae, in which scarcely any other flagellates occur; it does not ingest wood, and is not believed to be benefi- cial to its hosts. It occurs also in all classes of vertebrates. Man harbors Trichomonas tenax as a commensal in the mouth. T. vaginalis may be a serious pathogen. Penta- trichomonas obliqua (Moquin-Tandon) comb. nov.,l commensal (or pathogenic?) in the gut has at the anterior end a fifth flagellum separate from the other four (Kirby,^1943). icf. footnote, p. 165. 168] The Classification of Lower Organisms Family 4. Calonymphida [Calonymphidae] Grass! in Atti Accad. Lincei ser. 5, Rendiconti CI. Sci. 20, 1° Semestre: 730 (1911). Flagellates with radially symmetri- cal bodies including more than two nuclei and neuromotor systems, the latter of trichomonad type; entozoic in termites of subfamily Kalotermitinae. These flagellates ingest scraps of wood and are believed to contribute to the nutrition of their hosts. In Coronympha each cell contains one whorl of nuclei each with its separate neuro- motor system (Kirby, 1929). In Stephanonympha, the nuclei and neuromotor systems are so numerous as to form a spiral band of several cycles in the anterior part of the cell. In Calonympha, besides numerous neuromotor systems associated with nuclei, there are others free of any nucleus; in Snyderella, the two types of structures are independently multiplied. Order 4. Hypermastigina Grassi in Atti Accad. Lincei ser. 5, Rendiconti CI. Sci. 20, 1° Semestre: 727 (1911). Order Trichonyynphidea Poche in Arch. Prot. 30: 149 (1913). Order Hypermastigida Calkins Biol. Prot. 29"5 (1926). Order Lophomonadida Light in Univ. California Publ. Zool. 29: 486 (1927). Orders Joeniidca, Lophomonadina, Trichonymphina, and Spiratrichonym- phina, Grasse Traite Zool. 1, fasc. 1: 837, 851, 862, 916 (1952). Flagellates, mostly large and of radial symmetry, with single nuclei and indefi- nitely numerous flagella. Entozoic in roaches and in termites excluding those of family Termitidae. Lophomonas is to be regarded as the type. Cleveland (1925, 1926) found it possible, by starvation or by exposure to high pressures of oxygen or high temperatures, to rid insects of all of their intestinal flagellates or of some of the kinds. When completely freed of flagellates, wood roaches and termites of the lower families are able to remain alive only for a few weeks. The life of Termopsis is not prolonged by the presence of Streblomastix, and it is pro- longed only moderately by the presence of Trichomonas Termopsidis. But if infested with either Trichonympha Campanula or T. sphaerica, it can survive indefinitely on a diet of pure cellulose. Both species ingest the ground scraps of wood which reach the part of the intestine in which they occur; it is evident that they serve their hosts as agents of digestion. Cleveland's observations raise unanswered questions as to the occurrence of fixation of nitrogen; it is known only that termites are quite economical in their use of nitrogenous compounds available to them. The Hypermastigina have elaborate neuromotor systems. There is regularly a large centroblepharoplast. In what appears to be the relatively primitive type of cell divi- sion, as in Trichonympha (Kofoid and Swezy, 1919), the neuromotor system of the mother cell is divided between the daughter cells. In Spirotrichonympha (Cupp, 1930), only the centroblepharoplast divides; the neuromotor system of the mother cell remains attached to one of the daughter centroblcpharoplasts, while the other generates the remaining parts of a complete system. In Lophomonas (Kudo, 1926), and Kofoidia (Light, 1927), the neuromotor system of a dividing cell is absorbed or discarded, with the exception of the centroblcpharoplasts, from which new systems develop. In Trichonympha and Spirotrichonympha the details of nuclear division have much the appearance of meiosis. A double set of chromosomes appears, and the chromosomes form pairs which are divided in the spindle. It is supposed that this appearance is produced by a precocious splitting of the chromosomes. Phylum Protoplasta [ 169 In species of Trichonympha, Leptospironympha, and Eucomonympha from the wood roach Cryptocercus, Cleveland (1947, 1948) observed the syngamy of undiffer- entiated or diflFerentiated gametes; the appearance of the process is as though the egg ingested the sperm. Syngamy is followed immediately by meiosis. This means that vegetative individuals are haploid. Barhulanympha achieves without syngamy an al- ternation of haploid and diploid stages. Diploid cells are produced when a centro- blepharoplast fails to divide, with the result that the nucleus remains intact, while chromosomes appear and divide. Reduction division, by the separation of undivided chromosomes, occurs when a centroblepharoplast divides at an exceptionally early stage. Cleveland concluded that the early division of the central body is the event which primarily distinguishes meiosis from mitosis. It is possible that he has recog- nized an essential feature of the evolution of the sexual cycle. His words suggest the idea that the sexual cycle may have originated within the present group. This is an impossibility; the sexual cycle is a normal character of nucleate organisms, and is fully established in nucleate organisms far more primitive than these. There are fewer than one hundred known species of Hypermastigina. They are treated as seven families. 1. Body without segmented appearance. 2. Flagella distributed generally over the surface of the body or its anterior part. . . . Family 1. TRiCHONYMPHroA. 2. Flagella in spiral bands Family 2. HoLOMASTiGOTororoA. 2. Flagella in tufts. 3. Flagella in a single tuft Family 3. LoPHOMONAoroA. 3. Flagella in two tufts Family 4. HoPLONYMPHroA. 3. Flagella in four tufts Family 5. SxAUROjOENnDA. 3. Flagella in many tufts Family 6. KoForonoA. 1. Body with segmented appearance Family 7. Teratonymphida. Family 1. Trichonymphida [Trichonymphidae] Leidy ex Doflein Lehrb. Prot. ed. 3: 537 (1911). The numerous flagella distributed generally over the surface of the body or its anterior part. Trichonympha {Leidy opsis), Eucomonympha, etc. Family 2. Holomastigotoidida [Holomastigotoididae] Janicki in Zeit. wiss. Zool. 112: 644 (1915). Family S pirotrichonymphidae Grassi in Mem. Accad. Lincei CI. Sci. ser. 5, 12: 333 (1917). The numerous flagella arranged in spiral bands. Holo- m.astigotoides, S pirotrichonympha, etc. Family 3. Lophomonadida [Lophomonadidae] Kent Man. Inf. 1: 321 (1880). Family Joeniidae Janicki in Zeit wiss. Zool. 112: 644 (1915). The numerous flagella assembled in a single anterior tuft. Lophomonas, in cockroaches, all of the flagella directed forward. Joenia, Joenina, Joenopsis, etc., in termites, the outer flagella directed backward. Family 4. Hoplonymphida [Hoplonymphidae] Light in Univ. California Publ. Zool. 29: 138 (1926). The flagella assembled in two anterior tufts. Hoplonympha, Barhulanympha, etc. Family 5. Staurojoeninda [Staurojoenindae] Grassi in Mem. Accad. Lincei CI. Sci. ser. 5, 12: 333 (1917). The flagella assembled in four anterior tufts. Staurojoenina. Family 6. Kofoidiida [Kofoidiidae] Light in Univ. California Publ. Zool. 29: 485 (1927). The flagella fused at their bases into several bundles. Kofoidia, a single known species in Kalotermes. Family 7. Teratonymphida [Teratonymphidae] Koidzumi in Parasitology 13: 303 (1921). Family Cyclonymphidae Reichenow. Elongate and segmented, with a single 170] The Classification of Lower Organisms Fig. 32. — Hypermastigina : a-d, Trichonympha Campanula after Kofoid & Swezy (1919); a, cell x 250; b, division of centroblcpharoplast and formation of paradesmose, and c and d, earlier and later stages of mitosis x 500. e, f, g, Sperm, egg, and fertilization of Trichonympha sp. from the roach Cryptocercus after Cleve- land (1948). h, Hoplonympha Natator x 250 after Light (1926). i, Staurojoenina assimilis x 250 after Kirby (1926). j, Tcratonympha mirabilis after Koidzumi (1921). Phylum Protoplasta [171 nucleus in the anterior segment; flagella distributed generally on the surface, most abundant on an anterior beak. Teratonympha Koidzumi {Cyclonympha Dogiel), a single known species in Reticulitermes. Class 2. MYCETOZOA de Bary Order Dermatocarpi Persoon Syst. Meth. Fung, xiii (1801), in part. Suborder Myxogastres Fries Syst. Myc. 3: 3 (1829); suborder Trichospermi Fries op. cit. 1 : xlix (1832), in part. Suborder MyATomyce^^j Link 1833. Mycetozoen de Bary in Bot. Zeit. 16: 369 (1858); Zeit. wiss. Zool. 10: 88 (1859). Stamm Myxomycetes Ylatcktl Gen. Morph. 2: xxvi (1866). Class Mycetozoa de Bary ex Rostafinski Versuch Systems Mycetozoen 1 (1873). Division Mycetozoa and classes Myxogasteres and Phytomyxini Engler and Prantl Nat. Pflanzenfam. IITeil: 1 (1888). Division Myxothallophyta Engler in Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. 1: iii (1897). Stamm Myxophyta Wettstein Handb. syst. Bot. 1: 49 (1901). Division Phytosarcodina, Myxothallophyta, or Myxomycetes Engler Syllab. ed. 3: 1 (1903). Division Myxomycophyta Tippo in Chron. Bot. 7: 205 (1942). Order Mycetozoida Hall Protozoology 227 (1953). Organisms whose walled resting cells produce in germination anteriorly unequally biflagellate cells; these giving rise to bodies called plasmodia, being multinucleate bodies of amoeboid character. 1. Predatory, subaerial, producing macroscopic spore-bearing fruits. 2. Spores produced within the fruits Order 1. Enteridiea. 2. Spores produced on the surfaces of the fruits Order 2. Exosporea 1. Parasitic, not producing definite fruits Order 3. Phytomy.xii>a. Order 1. Enteridiea [Enteridieae] Rostafinski Vers. 3 (1873). Cohort Endosporeae and orders Anemeae, Heterodermeae, Reticularieae, Ain- aurochaeteae, Calcareae, and Calonemeae Rostafinski op. cit. Order Endosporea Lankester in Enc. Brit. ed. 9, 19: 840 (1885). Orders Protodermieae and Columniferae Rostafinski ex Berlese in Saccard) Sylloge7: 328,417 (1888). Cohorts Amaurosporales and Lamprosporales, with numerous orders with names in -aceae. Lister Monog. Mycetozoa 21-23 (1894). Subclass Myxogastres and orders Physaraceae, Stemonitaceae, Cribrariaceae, Lycogalaceae, and Trichiaceae Macbride North American Slime Molds 20 (1899). Subsuborder (!) Endosporinei Poche in Arch. Prot. 30: 200 (1913). Orders Physarales, Stemcnitales, Cribrariales, Lycogalales, and Trichiales Mac- bride op. cit. cd. 2 (1922). Order Liceales Ma. bride and Martin (1934). Suborder Eumycetozoina Hall Protozoology 230 (1953). 172 ] The Classification of Lower Organisms Predatory Mycetozoa producing macroscopic fruits, these producing internal uni- nucleate spores. The type is Lycogala, the sole genus of the order as originally published. The fruits of many examples are of the appearance of minute puffballs, and Per- soon and Fries classified them as puffballs; Fries took note that they are primitus mucilaginosi and made them a suborder distinct from the proper pufTballs. De Bary studied the non-reproductive stages; concluded "dass die Myxomyceten nicht dem Pflanzenreiche angehoren, sondern dass sie Thiere, und zwar der Abtheilung der Rhizopoden angehorig, sind"; and renamed the group Mycetozoen. This name was apparently first published in Latin form, in the category of classes, by de Bary's stu- dent Rostafinski. Conventional botany continues to list Myxomycetes as a class of Fungi; conventional zoology makes the group an order of Rhizopoda or Sarcodina. The spores germinate readily in water or appropriate solutions (Jahn, 1905; Gil- bert, 1929; Smith, 1929). Their nuclei usually divide once or twice, during or just after germination; thus each spore produces from one to four naked cells. It is in germinating spores that mitosis is most easily observed. Mitosis takes place in a clear area, about which some observers have found a persistent nuclear membrane. The spindle is sharp-pointed. Only a few observers (as Skupienski, 1927) have dis- cerned definite centrosomes. When the one or two divisions associated with germina- tion are complete, the flagella grow forth from the areas of the poles of the mitotic spindle. All earlier observers described the spores as uniflagellate, but Ellison (1945) and Elliott (1949) found them biflagellate. The flagella may be apparently equal or moderately unequal; or one of them may be very brief. Each nucleus remains con- nected to the base of the flagella by a conical body of clear protoplasm, the Geissel- glocke of Jahn (Jahn, 1904; Howard, 1931). The flagellate cells are not spores, but gametes; they fuse with each other. Skupien- ski (1917) affirms that they are of two mating types. Fusion is at first by pairs, and Howard (1931) found that each zygote develops into a plasmodium by itself. All other observers (de Bary, 1858, 1859; Cienkowski, 1863; Skupienski, 1917, 1927; Schiinemann, 1930) have found the zygotes to fuse with each other and with further gametes. The flagella are lost. The nuclei fuse in pairs; those which fail to find partners are digested. The cell formed by the fusion of zygotes and gametes is a young plasmodium. The term was coined by Cienkowski ( 1863, p. 326) : "Das Protoplasmanetz der Myxomy- ceten werde ich mit den Namen Plasmodium bezeichnen." The plasmodium nour- ishes itself in predatory fashion, on fungus spores, bacteria, and other digestible ob- jects, and grows accordingly. Mitosis occurs simultaneously in all nuclei of the plas- modium, and takes 20 to 40 minutes; it has accordingly only rarely been observed (Lister, 1893; Howard, 1932). Plasmodia do not ordinarily divide, but grow to great sizes. They are not very familiar objects because during most of their life they keep to dark and moist places, chiefly among vegetable remains. Drouth does not kill them; they can become dry and hard while retaining the capacity to resume activity upon the return of moisture. When an active plasmodium reaches a certain stage, its re- actions change; it moves out into the light and to dry places. A plasmodium in this stage is conspicuous, being of the form of a network which may be many centimeters in diameter, in some species brilliantly colored. The whole is a single naked protoplast. Each Plasmodium proceeds to produce a fruit or fruits. The entire mass may heap itself up, or it may break up into portions, large or minute. In species whose plas- modia break up into small fragments, each of these may secrete a column of lifeless Phylum Protoplasta [173 material, a millimeter or more in height, and ascend upon it. Each separate body of protoplasm secretes an external wall and begins to undergo cleavage within it. Har- per (1900) described the details of the process. All authorities agree that the nuclei undergo a flare of divisions at this time (Strasburger, 1884; Harper, 1900, 1914; Bisby, 1914). It is almost certain that there are two flares of division, constituting the meiotic process, but few authorities have positively affirmed this (Schiinemann, 1930)1. Cleavage is carried to the point of producing uninucleate protoplasts. While this is taking place, many species secrete a network of hollow tubes or a system of hollow fibers, called the capillitium, by deposition of lifeless material outside the cell membranes. In species which produce a true capillitium, all of the uninucleate protoplasts secrete walls and become spores. Strasburger found the capillitium and the walls of the spores to consist of impure cellulose; others have found no cellulose. In many species which do not produce a true capillitium, an analogous structure called a pseudocapillitium, consisting of solid bodies of various forms, is modelled from a part of the nucleate protoplasm which is deprived of its reproductive function and killed. In many species, much calcium carbonate is deposited in the wall, or both in the wall and in the capillitium or pseudocapillitium. A small separate fruit is called a sporangium. A fruit of the form of a large mass, or of many sporangia not completely separate, is an aethalium. The spores are re- leased by collapse of the outer wall. These organisms are of no known economic importance. There are some forty genera, between four and five hundred species. As Lister remarked, the same species occur everywhere: collections from Colombia (Martin, 1938) and from Mount Shasta (Cooke, 1949) consist entirely of familiar species. Rostafinski (1873) arranged the genera in two cohorts, seven orders, and nineteen tribes, the last with names in -aceae. His subsequent monograph of the group ( 1875) was regrettably published in a barbarous language, and is for nomenclatural purposes a nullity. All later systems are based on Rostafinski's original system. The group being essentially uniform, it is properly treated as a single order. Definite families were first established by Lankester, mostly under names which Rostafinski had applied to tribes. Berlese (in Saccardo, 1888) provided a complete set of names in -aceae, valid under botanical rules; Poche provided a complete set in -idae, valid under zoological rules. Authorities have differed moderately as to the list of families; here, somewhat arbitrarily, fourteen are maintained. 1. Capillitium none (order Cribrariales Mac- bride). 2. Producing separate sporangia, pseudo- capillitium none. 3. Sporangia shattering irregularly or opening through a terminal oper- culum Family 1 . Liceacea. 3. Sporangia opening through numer- ous pores, the walls becoming sieve- like Family 2. Cribrariacea. 2. Fruits aethalioid, pseudocapillitium present. iWhile the present work was in proof, Wilson and Ross (1955) established the point that meiosis occurs immediately before the formation of spores. 174 ] The Classification of Lower Organisms 3. Aethalia consisting of more or less separate sporangia. 4. Sporangia tubular, opening through terminal pores Family 3, Tubiferida. 4. Sporangia indistinct, their walls becoming freely punctured and converted into a reticulate pseudocapillitium Family 4. Retigulariacea. 3. Aethalia not consisting of distin- guishable sporangia Family 5. Lycogalacttoa. 1. Capillitium present. 2. Fruits without considerable deposits of calcium carbonate. 3. Spores black or dark, capillitial hairs smooth (order Stemonitales Macbride). 4. Fruits aethalioid, capilHtium poorly defined, without a cen- tral axis Family 6. Amaurochaetacea. 4. Fruits of separate sporangia with a definite capillitium in- cluding a central axis (colu- mella). 5. Capillitium spreading hor- izontally from the colu- mella Family 7. Stemonitea. 5. Capillitium spreading chiefly from the summit of the columella Family 8. Enerthenemea. 3. Spores pallid or yellow (order Tri- chiales Macbride). 4. Capillitial hairs smooth, un- branched or sparsely branched. 5. Capillitial threads hori- zontal, attached at both ends Family 9. Margaritida. 5. Capillitial threads run- ning at random, not at- tached at the ends Family 10. Perichaenacea. 4. Capillitium reticulate, sculp- tured, but not with spiral bands. . .Family 11. Arcyriagea. 4. Capillitial threads unbranched or sparsely branched, sculp- tured with spiral bands Family 12. Trighiagea. 2. Fruits containing considerable deposits of calcium carbonate (order Physarales Macbride). 3. Calcium carbonate both in walls and in capillitium Family 13. Physarea. Phylum Protoplasta [175 3. Calcium carbonate in walls but not in capillitium Family 14. DrovMiACEA. Family 1. Liceacea [Liceaceae] (Rostafinski) Lankester in Enc. Brit. ed. 9, 19: 841 (1885). Tribe Liceaceae Rostafinski Vers. 4 (1873). Order Liceaceae Lister Monog. Mycetozoa 149 (1894). Family Liceidae Doflein 1909. Family Orcadel- lidae Poche in Arch. Prot. 30: 200 (1913). Family Orcadellaceae Macbride N. Am. Slime Molds ed. 2: 203 (1922). Sporangia separate, sessile or stalked, without capil- litium or pseudocapillitium, the walls shattering irregularly or opening by means of a terminal operculum. Licea, Orcadella. Family 2. Cribrariacea [Cribrariaceae] (Rostafinski) Lankester 1. c. Tribe Crib- rariaccac Rostafinski op. cit. 5. Order Cribrariaceae Macbride N. Am. Slime Molds 20 (1899). Order Heterodermaceae Lister op. cit. 136. Family Cribrariidae Poche 1. c. The wall of the stalked fruit becoming sieve-like. Cribraria. Dictydium. Family 3. Tubiferida [Tubiferidae] Poche in Arch. Prot. 30: 200 (1913). Order Tubulinaceae Lister op. cit. 152 (1894). Family Tubulinidae Doflein 1909. Family Tubiferaceae Macbride in N. Am. Slime Molds ed. 2: 203 (1922). Aethalia consist- ing of tubular sporangia opening through terminal pores. Tubifer (its older name Tubulina preoccupied), Lindbladia, Alwisia. Family 4. Reticulariacea [Reticulariaceae] (Rostafinski) Lankester 1. c. Tribes Dictydiaethaliaceae and Reticulariaceae Rostafinski op. cit. 5, 6. Order Reticularia- ceae Lister op. cit. 156. Family Dictydiaethaliidae Poche I.e. Aethalia of indistinct sporangia whose walls become porous and are converted into a reticulate pseudo- capillitium. Reticularia, Dictydiaethallium, etc. Family 5. Lycogalactida [Lycogalactidae] Poche in Arch. Prot. 30: 201 (1913). Tribe Lycogalaceae de Bary. Order Lycogalaceae Macbride N. Am. Slime Molds 20 (1899). Y di.m.i\y Lycogalaceae Macbride and Martin Myxomycetes (1934). Aethalia with a pseudocapillitium, not divided into sporangia. Lycogala, the brownish fruits a few millimeters in diameter clustered on wood, of much the appearance of small puffballs. Family 6. Amaurochaetacea [Amaurochaetaceae] (Rostafinski) Berlese in Sac- cardo Sylloge 7: 401 (1888). Tribe Amaurochaetaceae Rostafinski op. cit. 8. Order Amaurochaetaceae Lister op. cit. 134. Family Amaurochaetidae Doflein 1909. Fruits aethalioid with dark spores and a poorly defined capillitium without a central axis. Amaurochaete. Family 7. Stemonitea Lankester in Enc. Brit. ed. 9, 19: 841 (1885). Tribes Stemo- nitaceae and Brefeldiaceae Rostafinski op. cit. 6, 8. Families Stemonitaceae and Brefeldiaceae Berlese in Saccardo op. cit. 390, 402. Order Stemonitaceae Macbride N. Am. Slime Molds 20 (1899). Family Stemonitidae Doflein 1909. Families Bre- feldiidae and Stemonitidae Poche op. cit. 202. Sporangia with dark spores and a capillitium of smooth threads spreading from a central axis, the columella. Stemo- nitis, comm.on, the clustered stalked fruits of the appearance of minuscule dark bottle-brushes. Brefeldia, Comatricha; Diachea, exceptional in containing much lime in the stalk and wall. Family 8. Enerthenemea Lankester 1. c. Tribes Echinosteliaceae and Enerthene- maceae Rostafinski op. cit. 7, 8. Families Echinosteliaceae and Enerthenemaceae Berlese in Saccardo op. cit. 389, 402. Family Lamprodermaceae Macbride N. Am. Slime Molds ed. 2: 189 (1922). Like Stemonitea, in which this family has usually been included, but the capillitium attached chiefly at the summit of the columella. Enerthenema, Clastoderma, Lamproderma, Echinostelium. 176] The Classification of Lower Organisms Family 9. Margaritida [Margaritidae] Doflein 1909. Order Margaritaceae Lister op. cit. 202. Family Dianemaceae Macbride N. Am. Slime Molds ed. 2: 237 (1922). Sporangia with pale or yellow spores and a capillitium of smooth threads attached at both ends. Dianema, Margarita. Family 10. Perichaenacea [Perichaenaceae] (Rostafinski) Lankester 1. c. Tribe Perichaenaceae Rostafinski op. cit. 15. Sporangia with pale or yellow spores and a capillitium of unattached smooth threads. Perichaena, Ophiotheca. Family 11. Arcyriacea [Arcyriaceae] (Rostafinski) Lankester 1. c. Tribe Arcyri- aceae Rostafinski op. cit. 15. Order Arcyriaceae Lister op. cit. 182. Family Arcyriidae Doflein 1909. Sporangia with pale or yellow spores and a reticulate capillitium, usually sculptured, but not with spiral bands. Arcyria, Lachnobolus. Family 12. Trichiacea [Trichiaceae] (Rostafinski) Berlese in Saccardo Sylloge 7: 437 (1888). Tribe Trichiaceae Rostafinski op. cit. 14. Family Trichinaceae Lankes- Fig. 33. — Mycetozoa. a-f, Spore, germination, gametes, syngamy, and zygote of Physarum polycephalum after Howard (1931) x 1,000. g-1, Stages of mitosis in the Plasmodium of Physarum polycephalum after Howard ( 1932) x 2,000. m-o. Stages of mitosis in the plasmodium of Trichia after Lister (1893) x 1,000. p, Cleavage in the developing fruit of Physarum polycephalum after Howard (1931) x 1,000. q, Capillitium and spores of Lepidoderma Chailletii x 1,000. r-W, fruits of Myce- toza X 5; r, Sternonitis splcndens; s, Lycogala cpidcndrum; i, Lcocarpus fragilis; U, Lepidoderma Chaillettii; v, Physarum notabile; w, Hemitrichia intorta. Phylum Protoplasta [177 ter 1. c; the genus Trichina does not belong to this family! Order Trichiaceae Mac- bride N. Am. Slime Molds 20 (1899). Family Trichiidae Doflein 1909. Sporangia with pale or yellow spores, the capillitium of free threads, unbranched or sparsely branched, marked with spiral bands. Trichia, Hemitrichia, Oligonema, Calonema. Family 13. Physarea Lankester 1. c. Tribes Cienkowskiaceae, Physaraceae, and Spumariaceae Rostafinski op. cit. 9, 13. Families Cienkowskiaceae , Physaraceae, and Spumariaceae Berlese in Saccardo op. cit. 328, 329, 387. Order Physaraceae Macbride N. Am. Slime Molds 20 (1899). Family Physaridae Doflein 1909. Fruits sporangial or aethalioid, with capillitium, both wall and capillitium containing considerable deposits of calcium carbonate. Physarum, with some seventy-five species, is the most numerous genus of Mycetozoa; the little gray sporangia may be spherical or irregular, sessile or stalked. Fuligo septica produces dirty yellow aethalia reaching several cen- timeters in diameter on vegetable trash; observed on spent tan bark, it has the com- mon name of flowers of tan. Badhamia, Craterium, Leocarpus, Chondrioderma, Spumaria, etc. Family 14. Didymiacea [Didymiaceae] (Rostafinski) Lankester 1. c. Tribe Didy- miaceae Rostafinski op cit. 12. Order Didymiaceae Lister op. cit. 93. Family Didy- midae Doflein 1909. Family Didymiidae Poche op. cit. 202. Family Collodermata- ceae Macbride and Martin Myxomycetes 145 (1934). Sporangia with deposits of calcium carbonate in the wall and a simple capillitium free of mineral deposits. Didymium, Leangium, Lepidoderrna, Colloderma. Order 2. Exosporea (Rostafinski) Lankester in Enc. Brit. ed. 9, 19: 841 (1885). Cohors Exosporeae Rostafinski Vers. 2 (1873). OrAtr Ectosporeae Y.ng\tr ?>y\\2ih. 2 (1892). Order Ceratiomyxaceae (Schroter) Lister Monog. Mycetozoa 25 (1894). Subsuborder (!) Exosporinei Poche in Arch. Prot. 30: 200 (1913). Organisms of much the character of the Enteridiea, but the spores forming a single layer on the surface of the fruits. There is a single family with only one well-marked species. Family Ceratiomyxacea [Ceratiomyxaceae] Schroter (in Engler and Prantl, 1889). Ceratiomyxa Schroter [Ceratium Albertini and Schweinitz, 1805, non Schrank, 1793); C. fruticulosa (O. F. Miiller) Macbride. The fruits are white pillars, sometimes branched, 1-2 mm. tall, of secreted material. Each spore of the single superficial layer generates a microscopic stalk and ascends upon it before becoming walled. Meiosis then takes place, making the spores 4-nucleate; the chromosome number is cut from 16 to 8 (Gilbert, 1935). In germination, the contents of the spore are re- leased as a single amoeboid protoplast, whose nuclei divide once; the cell then divides into eight, and these generate flagella (Rostafinski, 1873; Jahn, 1905; Gilbert, 1935). Order 3. Phytomyxida Calkins Biol. Prot. 330 (1926). Class Phytomyxini Engler and Prantl Nat. Pflanzenfam. II Teil: 1 (1889); class Phytomyxinae op. cit. I Teil, Abt. 1: iii (1897). Order Phytomyxinae Campbell Univ. Textb. Bot. 71 (1902). Class Plasmodiophorales Engler Syllab. ed. 3: 1 (1903). Order Plasmodiophorales Sparrow in Mycologia 34: 115 (1942). Suborder Plasmodia phorina Hall Protozoology 228 (1953). Intracellular parasites chiefly of higher plants, attacking also algae, Oomycetes, and beetles, being naked multicellular plasmodia producing walled resting cells, 1781 The Classification of Lower Organisms the walls containing no cellulose; these releasing naked infective colls with paired unequal simple flagella. This inconsiderable group was made known by the discovery of Plasmodiophora Brassicae, the agent of the clubroot disease of cabbage, by Woronin (1878). The proper place of the group in classification has been a puzzle; some students treat it as a class of myxomycetes, others as an order of chytrids. The known characters — paired unequal simple flagella; cells naked in the vegetative condition; and non-pro- duction of cellulose — assure us that this group has nothing to do with proper chytrids, nor with Oomycetes of chytrid body type. The traditional association with myxomy- cetes is tenable. Alternatively, the group would not be out of place next to order Rhizoflagellata (anyone who chooses to put it there should take note that the class name Phytomyxini is older than Zoomastigoda). The Plasmodium causes often much hypertrophy of the host tissue. In some forms the mature plasmodium becomes walled; the protoplast undergoes cleavage into uni- nucleate portions; these become swimming cells and are released through a discharge tube. These forms are of much the appearance of Lagenidialea. In the majority of the group the naked plasmodium undergoes cleavage; the resulting protoplasts be- come walled; the resulting spores or cysts, released by decay of the host, discharge their contents as one or two swimming cells. Ledingham ( 1939) and Sparrow ( 1947) report both types of development as occurring in Polyniyxa. Karling (1944) found the walls to contain no cellulose. Ellison (1945) found the flagella to be simple. iKyuiU/Tnui wuium/^iiiMiivnirm- Fig. 34. — Ceratiomyxa jruticulosa. a. Fruits x 5. b-q, reproductive processes after Gilbert (1935); b, young spores on the surfaces of the fruit; c, d, the same raised on stalks; e^ f, heterotypic division; g, homeotypic division; h, the mature spore ou its stalk; i-n, germination and subsequent processes: the amoeboid protoplast passes through a "thread stage" before rounding up and dividing into four and then into eight; o, production of flagcllum; p, "zoospore" (gamete); q, gametes fusing to initiate the plasmodium. All x 1,000 except Fig. a. Phylum Protoplasta [179 In the growing plasmodium, a nucleus which is not dividing contains an endosome ("nucleolus"). During mitosis, which occurs within the intact nuclear membrane, the endosome becomes elongate, and a ring of chromatin, within which separate chromosomes have not been distinguished, forms about its middle. The resulting "cru- ciform" figure resembles some which have been seen in trypanosomes. The nuclear divisions which occur immediately before cleavage are of a different character: no en- dosome is seen, but there is a spindle with centrosomes at the poles, and definite chromosomes are present. The occurrence of these two types of nuclear division has been noted by every careful observer, Schwartz (1914), Home (1930), Cook (1933), Ledingham (1939), and Karling (1944). Home was probably correct in supposing the divisions which precede cleavage to be meiotic. Conjugation of the flagellate cells of Spongospora has been observed. There are monographic accounts of the Phytomyxida by Cook ( 1933) and Karling (1942). The group may be treated as a single family with a dozen genera and about twenty-five species. Family Plasmodiophorea [Plasmodiophoreae] Berlese in Saccardo Sylloge 7 : 464 (1888). Family Plasmodiophoreen Zopf Pilzthiere 129 (1885). Family Plasmodio- phoraceae Engler Syllab. 1 (1892). Family Woroninaceae Minden 1911. Families Phytomyxidae and Woroninidae Poche in Arch Prot. 30: 198 (1913). Plasmodio- phora, Polymyxa, Spongospora, and Sorosphaera attack land plants; Tetramyxa, Ligniera, and Sorodiscus, chiefly aquatic seed plants; Woronina and Octomyxa, Oomycetes; Phagomyxa, brown algae; Sporomyxa (Leger, 1908) and Mycetosporid- ium, beetles. Class 3. RHSZOPODA Siebold Order Foraminiferes d' Orbigny in Ann. Sci. Nat. 7: 128, 245 (1826). Order Foraminifera Zborewski 1834. Rhizopodes Dujardin in Compt. Rend. 1: 338 (1835). Class Foraminifera d'Orbigny in de la Sagra Hist. Cuba vol. 8 (1839). Order Polythalamia Ehrenberg in Abh. Akad. Wiss. Berlin (1838) : table 1 ( 1839) . Class Rhizopoda and orders Monosomatia and Polysomata Siebold in Siebold and Stannius Lehrb. vergl. Anat. 1 : 3, 11 (1848). Reticulosa Carpenter 1862. Stamm Rhizopoda and Class Acyttaria Haeckel Gen. Morph. 2: xxvii (1866). Thalamophora R. Hertwig Hist.Radiolar. 82 (1876). Class Reticidaria Lankester in Enc. Brit. ed. 9, 19: 845 (1885). Order Reticulosa Poche in Arch. Prot. 30: 203 (1913). Order Granuloreticulosa de Sacdeleer in Mem. Mus. Roy. Hist. Nat. Belgique 60: 7 (1934). Order Foraminiferida Hall Protozoology 250 (1953). Amoeboid organisms, the pseudopodia of the character of rhizopodia, i.e., fine, freely branching and anastomosing; producing shells, these usually calcareous; com- monly reaching macroscopic dimensions; mostly marine. The first examples of rhizopodes mentioned by Dujardin were milioles, vorticiales, and le gromia: the genus Miliola is to be construed as the type. These organisms, the proper rhizopods, are in general usage called Foraminifera, but that name was orig- inally applied in the categoiy of orders. 180] The Classification of Lower Organisms Fig. 35. — Life cycle of "Tretomphalus," i.e., Discorbis or Cymbalopora, from Myers (1943); 1-3, microspheric individuals, in 3 releasing young megalospheric individuals; 4-8 megalospheric individuals; 9-12, gametes and syngamy. Phylum Protoplast a [181 The individual rhizopod originates as a minute amoeboid cell which secretes a shell from which the pseudopodia project. In the fresh-water forms, each protoplast, after moderate growth, divides into two, one of which retains the original shell while the other secretes a new one. In some of the marine forms, the original protoplast, having a cylindrical or irregular shell, enlarges this as it grows. In the great majority of the group, the original shell, called the proloculus, is of definite size and form and has a constricted orifice. When the protoplast reaches a certain stage, it expands, pro- trudes from the orifice, and secretes an extension of the shell in the form of a second chamber. In some few examples, the second chamber is the final one, being capable of indefinite extension. But again in the great majority, the second chamber, although diff'erent from the proloculus, resembles it in being definite in form and in having a constricted orifice. After further development, the protoplast again protrudes through the orifice and secretes a third chamber, generally of the same form as the second, though often larger. Repetition of this process produces macroscopically visible bodies. Even though becoming a centimeter or more in diameter, the individuals continue to be single cells. As a result of different patterns of growth, the developed shells are of highly varied forms, linear, globular, or coiled in one plane; trochoid or rotaloid, that is, helical, of the form of a low cone; of the form of high cones; or screw-like, with the chambers in fixed longitudinal rows. The grov/th pattern may change during the life of the individual. There are apparently degenerate forms, simple or irregular. It is highly probable that some of the forms have evolved repeatedly. The shells may be of gelatinous material or of chitin, without or with imbedded grains of sand. Exceptionally, they are siliceous. They are sometimes of crystallized calcium carbonate with imbedded grains of sand. In the bulk of the group they consist of crystallized calcium carbonate without foreign matter, and are of either of two t>'pes of texture: vitreous, that is, hyaline, and punctured by numerous pores a few microns in diameter; or porcellanous, white by reflected light and amber by trans- mitted light, and with no perforations except the proper orifices. In fossil shells, other textures than these may occur; it is supposed that these are products of modification during preservation. Some of the textures, like some of the forms, are believed to have evolved repeatedly. Most rhizopods occur in two forms which are most readily distinguished by the size of the proloculi. This was first pointed out by Munier-Calmas, 1880; who, jointly with Schlumberger, 1885, designated the smaller and larger proloculi re- spectively microsperes and megaspheres. Lister (1895), by study in culture of Elphi- dium crispiirn [Polystomella crispa Lamarck), showed that the two forms are alter- nate generations. He observed that the microspheric cells become multinucleate during growth, while the megalospheric cells remain uninucleate until just before reproduction. The reproduction of the megalospheric cells is by release of numerous minute biflagellate cells. Schaudinn (1902) confirmed much of what Lister had observed. He was mistaken in describing nuclear division (except just before the production of the swimming cells) as non-mitotic; and correct in identifying the swimming cells as gametes. Winter (1907) observed a similar life cycle in Peneroplis, but described the gametes as having solitary flagella. Myers" (1934, 1935, 1936), dealing with Patellina and Spirillina, described the details of mitosis. This takes place within an intact nuclear membrane, and is com- pleted by its constriction. The spindle is blunt-ended; there is no evidence of centre- 182 ] The Classification of Lower Organisms somes. The chromosomes are numerous, long, and slender; the mitotic figures re- semble those of Pyrrhophyta. Reduction of the chromosome number is said to be effected by a single nuclear division, the last one before the formation of gametes, which cuts the chromosome number of Patellina from 24 to 12, and that of Spirillina from 12 to 6. Before they reach this stage, the megalospheric individuals have gathered themselves in clusters of two or more within cyst walls consisting of secreted gelatinous matter and scraps from the neighborhood. Gametes from one individual are unable to unite with each other. The gametes are amoeboid, positively without flagella. In Discorbis and Cymbalopora, however, Myers (1943) observed the produc- tion of biflagellate gametes. Le Calvez (1950) has cleared up various questions raised by earlier studies. Some forms, as Discorbis orbicularis, appear to lack a sexual cycle. Patellina and Spirillina produce amoeboid gametes 40-50[.i in diameter. Most rhizopods produce biflagellate gametes 1.5-4[i long. Le Calvez found the flagella definitely unequal. In Discorbis mediterranensis he showed that the megalospheric individuals are of two mating types. Earlier zoologists, apparently misled by familiarity with the normal life cycle cf animals, had identified meiosis as occurring at the time of gametogenesis; it is the fact, on the contrary, that it occurs in the last two nuclear divisions in the micro- spheric individuals. The megalospheric and microspheric stages of rhizopods are respectively haploid and diploid, like the gametophytes and sporophytes of plants. With the possible exception of some of the one-chambered fresh water forms, the rhizopods are clearly a natural group. The fresh water forms appear to intergrade with organisms which Pascher identified as chrysomonads. The shells of dead rhizopods may under appropriate conditions be preserved through geologic ages. Natural chalk consists of shells of Textularia mixed with coc- coliths. Certain forms of limestone consist chiefly of shells of Miliola. Certain fossil rhizopods have long been known as indicators of division of geologic time. Since about 1917, it has been found that the whole group offers one of the beautiful illustrations of evolution as related to geologic time: the shells of rhizopods found under magnifi- cation in a particular stratum serve promptly and precisely to identify it. The services of experts on "Foraminifera" have acquired a high economic value in the petroleum industry: these experts have found themselves promoted from the status of pure biologists to that of economic geologists. Among some eleven hundred genera which have been published, Galloway (1933) maintains 542. Of the number of species one can only say that it is a matter of thousands, but probably not many tens of thousands. Economic micropaleontologists find themselves dealing with great numbers of forms which are slightly, yet signifi- cantly, distinct. They find it expedient not to name these, but to identify them by comparison with available collections. Some of the marine and fossil forms are similar, on a small scale, to the animal Nautilus, and Linnaeus placed some of them in that genus. Montfort and Lamarck treated them as several genera of mollusks. In first distinguishing these organisms as the order Foraminiferes of class Cephalopodes, d'Orbigny intended to contrast them with Nautilus, in whose shells a series of chambers arc connected, not by holes (fora- mina) but by cylindrical tubes. Dujardin ( 1835) found that his Rhizopodes are with- out definite organs. Their shells enclose a clear semiliquid substance; their apparent tentacles are merely temporary structures, formed of this substance, thrust forward in the direction of the movement of the shell and withdrawn as it advances. Dujardin named this substance sarcode; it is, of course, the same which has since been called Phylum Protoplasta [ 183 protoplasm. The effect of his discoveries was to show that the rhizopods or Foramini- fera are not mollusks, but one-celled organisms. Very much taxonomic study has been given to this interesting group. The standard system, in the modern period of practical concern with the group, has been that of Cushman (1928). Galloway (1933), attempting to recognize phylogeny and concluding that certain types of form and texture of shells have evolved repeatedly, has radically revised Cushman's system and set up a system of thirty-five families. The following survey of the group is based on Galloway's system. The names applied to the families are those which he has cited as the oldest, and the groups treated as orders are the blocks of families which to him appeared natural. 1. Shell one-chambered, or of a proloculus fol- lowed by one other chamber, not of a series of similar chambers Order 1. Monosomatia. 1. Shell a series of similar chambers. 2. Shell porcellanous, imperforate Order 2. Miliolidea. 2. Not as above. 3. Not specialized as in the following orders Order 3. Foraminifera. 3. Shell hyaline, perforate, typically trochoid, i.e., having the succes- sively larger chambers helically ar- ranged so that all may be seen from one side and only the last whorl from the other Order 4. GLOBiGERiNroEA. 3. Chambers of the fundamentally planispiral shell with specialized walls containing channels or pro- ducing chamberlets Order 5. Nummulitinidea. Order 1. Monosomatia (Ehrenberg) Siebold in Siebold and Stannius Lehrb. vergl. Anat. 1: 11 (1848). Monosomatia Ehrenberg in Abh. Akad. Wiss. Berhn (1838) : table 1 (1839). Order Astrorhizidea Lankester in Enc. Brit. ed. 9. 19: 846 (1885). Order Imperforida Delage and Herouard Traite Zool. 1: 107 (1896). Order Archi-Monothalamia Calkins Biol. Prot. 354 ( 1926) . Rhizopoda consisting of a single chamber, or of a proloculus followed by one other chamber; exceptionally, after passing through a stage of this character, producing a series of similar chambers. Family 1. Allogromiida [Allogromiidae] Cash and Wailes. Minute, with one- chambered chitinous or gelatinous shells, usually subglobular; large in fresh water. Allogromia Rhumbler; Mikrogromia Hertwig, the pseudopods of sister cells retaining contact so that small colonies are formed; etc. Family 2. Astrorhizida [Astorhizidae] Brady (1881). Family Astrorhizina Lankes- ter (1885). Family Astrorhizidaceae Lister. Families Rhizamminidae , Saccammini- dae, and Hyperamminidae Cushman. Shell of agglutinated foreign material, usually elongate, often branched, but not coiled. In Astrorhiza there is a central chamber from which grow elongate arms. In Rhizammina, the shell is tubular, open at both ends; in Bathysiphon it is a tube closed at one end; in Hyperammina a proloculus is formed before the extended tube. 184] The Classification of Lower Organisms - ^ / m\^■^V^//'":^^^^^.^V^\\■•\\ Fig. 36 — Shells of Rhizopoda. a, Ophthalimidium. h, c, Triloculina. d, Verte- bralina. e, Peneroplis. f, Archaias x 25. g, Nodosaria. h, Dcntilina. i, Flabel- lina. j, Lagena. k, 1, Nonion. m, n, Rotalia. o, Globigerina. x 50 except as noted. Phylum Pro