The Kingdoms of Organisms: From a Microscopist's Point of View

The Kingdoms of Organisms: From a Microscopist's Point of ViewAuthor(s): John O. CorlissSource: Transactions of the American Microscopical Society, Vol. 105, No. 1 (Jan., 1986), pp. 1-10Published by: Wiley on behalf of American Microscopical SocietyStable URL: http://www.jstor.org/stable/3226544 .

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TRANSACTIONS

of the

American Microscopical Society VOL. 105 JANUARY 1986 NO. 1

The Kingdoms of Organisms-From a Microscopist's Point of View'

JOHN 0. CORLISS

Department of Zoology, University of Maryland, College Park, Maryland 20742, U.S.A.

Abstract. First, the historical background with respect to recognition of kingdoms of

organisms is traced, emphasizing the strength of authoritarianism, territoriality, and tradition in the long maintenance of two such taxa only, the Animalia and the Plantae. Hogg and Haeckel, 125 years ago, appreciated the importance of microscopical data but failed to "sell" biologists on the idea of a third kingdom, the Protista. Within the past two decades, the highly significant evolutionary concept of a prokaryotic-eukaryotic split of the biotic world has been completely accepted. Now (especially during the past 10-12 years), the protists, under one definition or another, are being seriously reconsidered as a

separate assemblage of "lower" eukaryotes, although controversies rage over important details. Based primarily on differences in the kind and degree of cellular organization (along with presence or absence of tissues), four definitive eukaryotic kingdoms are rec-

ognized and described here and considered sufficient for representation of the entire

superkingdom EUKARYOTA: the Animalia, Plantae, Fungi, and Protista. Special attention is given to the author's neo-Haeckelian view of the last-mentioned kingdom, for him

comprised of some 18 supraphyletic assemblages that, in turn, are considered to embrace 45 quite distinct phyla.

Until quite recent years, a microscopist interested in biological materials- like any general biologist-would have experienced no problem in identifying the kingdoms of organisms. No matter what his or her professional interest, there were only two, one represented by the animals of the zoologist, the other by the plants of the botanist. From the time of Aristotle through Darwin and Haeckel and, alas, still today in the minds of some practicing biologists, but more generally up until a quarter of a century ago, those two great Linnaean kingdoms, the Animalia and the Plantae, were standardly separated by a small set of easily distinguishable-thus predominantly macroscopic-characteristics. Although still holding true in large measure, these attributes were limited to the obvious, superficial, "key" characters; and the many exceptions to them,

1 Most of this paper is based directly on an oral presentation (for an abstract of which, see Corliss, 1984a) made at meetings of professional societies convened in Denver, Colorado in late December 1984. Support of National Science Foundation Grant BSR 83-07113 is gratefully acknowledged.

TRANS. AM. MICROSC. SOC., 105(1): 1-10. 1986. ? Copyright, 1986, by the American Microscopical Society, Inc.



TRANS. AM. MICROSC. SOC.

some long known, were dutifully ignored, at least at the high taxonomic level of kingdom.

How many and what were these attributes so convenient in making clear the existence, separation, and adequacy of solely two kingdoms to describe the biotic world? Simplistically, one may suggest that there were only four that sufficed. Animals were all colorless (i.e., non-pigmented from a photosynthetic point of view); all were actively motile; their nutrition was phagotrophic; and their cells were "naked" (i.e., no cell walls). By contrast, plants were pigmented (basically green); inactive (non-motile, most commonly because of being rooted in soil); their nutrition was solely autotrophic (by photosynthesis); and they possessed cell walls of cellulose. In both cases, the microscope (coupled with chemical analysis) was necessary for determination of only the fourth char- acter.

IMPACT OF DISCOVERY OF MICROORGANISMS

It was more or less by chance, with the great rise of microscopy as a science and thus the unearthing of microorganisms in some abundance (Corliss, 1978, 1979), that botanists, of the nineteenth century in particular, were by and large the first to discover, and of course lay claim to, species of algae. They also established a taxonomic home for the bacteria, while the general biology of these microorganisms, especially the pathogenic ones, was left to the medical profession or to a new group of scientists soon to become known as bacteriol- ogists or microbiologists. Finally, the plant scientists early claimed both the microscopic as well as the macroscopic fungi, too, seemingly paying little attention-in all three of these cases, but most flagrantly in the last-to the fact that at least three of the four major "plant" characteristics enumerated above were clearly violated in such taxonomic decisions. At the same time, zoologists-again perhaps mainly by chance-became fascinated by their discoveries of vast numbers of the so-called proto-zoa, and eagerly took them into the animal fold with no twinge of taxonomic conscience.

As authoritarianism grew, notably in the great universities, herbaria, and museums of Germany during the 1800's, and as it was combined with jealously guarded territoriality, the classification system became fixed by tradition (Cor- liss, 1983a,b). Thus-to abbreviate the story drastically here-the imposition downward of perceived major plant characteristics resulted in the acceptance (which essentially no one dared to question) of bacteria, algae, and fungi of all kinds taxonomically as plants; and in parallel, the similar imposition downward of so-called animal characters resulted in the obvious inclusion of pro- tozoan species of diverse kinds as animals. So there came to be "mini-plants" and "mini-animals," although such terminology was never actually employed for the largely aquatic, microscopic, unicellular, or filamentous forms of life involved. Incidentally, the discoveries of paleobiologists and micropaleobiolo- gists were of no particular help in challenging the two-kingdom system, so sternly taught and so firmly entrenched was it both in textbooks and in the indisputable monographic research literature produced by the masters of the time.

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VOL. 105, NO. 1, JANUARY 1986

Thus, in retrospect, there was no positive impact of the discovery of microorganisms sensu lato with respect to altering the classification scheme for living things. The important morphological findings of early protozoologists and phycologists also trained in microscopy, findings that revealed a plethora of taxonomically differentiating characters, went essentially unheeded. Worthy of at least passing mention, however, were the valiant single-handed efforts of nineteenth century workers like J. Hogg and, especially, Ernst Haeckel who, some 120-125 years ago, attempted to free the microscopic forms of life from cate- gorization as "regular" plants and animals. However, such efforts failed to receive support, with some of the criticism leveled against them admittedly quite valid, particularly from the vantage point of today's knowledge. Some revival of interest in Haeckel's iconoclastic third kingdom Protista occurred in the 1930's and 1940's, culminating in Copeland's (1956) masterful treatise, but apparently to no lasting avail.

AN EVOLUTIONARY DIVISION OF THE BIOTIC WORLD

In about 1960, resurrecting and embellishing an idea originally conceived some 20 years earlier by the great French protistologist and microscopist Edouard Chatton, Roger Stanier and colleagues (e.g., see Stanier & van Niel, 1962) made a formal proposal to view the whole world of life in a totally different way, dividing it anew into two great groups, but on an evolutionary basis that was as startling-at the time-as it was significant and inspirational. Purely by coincidence, incidentally, this approach added a further blow to the possible revival of Haeckel's third kingdom, since it left to one side any conventional morphological/taxonomic considerations.

In brief, since the story is a very familiar one to most biologists today, the Chatton-Stanier concept of a kingdom (better, superkingdom) Prokaryota for bacteria (in the broadest sense) and a second superkingdom Eukaryota for all other organisms has been widely accepted with enthusiasm. Although the em- phasis originally, as implied in the apt group-names chosen, was on nuclear characteristics, numerous and other molecular and macromolecular differences are now known for separation of these two phylogenetically as well as taxonomically distinct assemblages of living things. Even from a purely descriptive (anatomical, if you will) point of view, we may note that the macromolecular composition of a prokaryotic cell is clearly different from that of the eukaryotic cell and organism. Even with respect to size, members of the more primitive group are usually one or more orders of magnitude smaller in linear dimen- sions, and thus strikingly more so in volume.

Little need be said here about the cytoarchitecture of the prokaryotic cell, but perhaps worth stressing is its total lack of discrete membrane-bound sub- cellular organelles: for example, there are no mitochondria, chloroplasts, en- doplasmic reticulum, etc. in bacteria. In the cytoplasm are ribosomes (of small size), sometimes photosynthetic pigments, and nuclear material typically represented by a single circular strand of DNA not enclosed in a membrane. Flagella, present on the body of some species, are structurally unlike the type displayed by flagellated/ciliated eukaryotes, with differences also in the kind

3




and composition of the microtubular proteins involved. With rare exception, prokaryotes are surrounded by a rigid cell wall, typically containing muramic acid. (Note the obvious dependency on microscopy, including electron microscopy, for the bulk of the characters aforementioned.)

Several kingdoms may be commendably recognizable within the superkingdom Prokaryota (at least the Archaebacteria and the Eubacteria; e.g., see Stackebrandt & Woese, 1984; Woese, 1981; Woese & Fox, 1977), but such a topic is beyond consideration in the present essay.2 Nevertheless, their taxonomic removal in toto from the eukaryotic assemblages may be hailed here as one of the most significant advances of the twentieth century in systematics and evolutionary biology.

RECONSIDERATION OF EUKARYOTIC SYSTEMATICS

Although interest in the compelling evolutionary prokaryotic/eukaryotic schism has dominated much of the general field of biological systematics for some years during the past quarter of a century, resurrection of the Hogg- Haeckelian idea of the separation of the so-called protists or protoctists (however defined) from the conventional and still powerfully entrenched (e.g., see Parker, 1982) pair of eukaryotic kingdoms of plants and animals has become popular in recent years. Leadership for such renewed and persistent attention to what one might call the "lower" eukaryotes came first not from taxonomists or cytologists but mainly from ecologists and molecularly inclined geneticists (e.g., see Margulis, 1970, 1974; Whittaker, 1969, 1977; Whittaker & Margulis, 1978). About the same time, lobbying for the separation (from plants) of the

fungi reappeared: equal taxonomic status for equal uniqueness, as it were. Evolutionary biologists, particularly persons with botanical degrees, interest-

ingly enough, soon joined the fray (e.g., see Cavalier-Smith, 1981, 1983; Dodge, 1979; Dodson, 1971; Jeffrey, 1971, 1982; Leedale, 1974; Sleigh, 1979; Staro- bogatov, 1984; Stewart & Mattox, 1975, 1980; Taylor, 1978), and the number of separate eukaryotic kingdoms ranged from three or four to many. Data from cytological, particularly ultrastructural, studies began to be appreciated, along with findings from sophisticated biochemical and molecular approaches.

Space does not permit any in-depth consideration of the numerous propo- sitions, promulgations, insights, and proposals put forth related to this overall topic; especially during the past 8-10 years, there has been a mushrooming interest in evolutionary interrelationships of taxonomically high-level groups of different organisms. Disagreements that have inevitably arisen have cen- tered around problems of degrees of discreteness (among the various separate

2 Actually, as Stackebrandt & Woese (1984) have very recently stressed, it may be better-more evolutionarily sound-to think of three "primary" superkingdoms-Archaebacteria, Eubacteria, and Eukaryota-since the distance/difference between the first two prokaryotic groups may be considered at least as great as that between either of them and the third. But such a topic, although exceedingly important, is essentially irrelevant to the principal theme of the present paper. Inci- dentally, in agreement with the views of practically all modern biologists, I have left the viruses completely to one side taxonomically: these acellular entities (perhaps not properly called "organisms" at all) are neither prokaryotes nor eukaryotes under my definitions of these assemblages.

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kingdoms espoused), the nature of characteristics employed (e.g., apomorphic vs. plesiomorphic features), weighting of characters, and bases for drawing "dividing lines" at one level or another. Factors of convergent evolution obviously arise, and they pose problems difficult of resolution with respect to most of the kinds of material available for study and analysis. Some critics (of multiple kingdoms) point out that nutritional differences are overrated. Other (or the same) workers, agreeing with Haeckel's adversaries of a century ago, feel strongly that the protists are (remain) a motley assembly of unrelated forms and that the most generous way to look upon them is as a level of structural organization only, an evolutionary way-station or "horizontal" grade undeserving of separate highest-level taxonomic isolation as an integrated or intra-related kingdom of organisms. Still others accept the "uniqueness" of "protists" but would disperse them among a (sometimes large) number of separate kingdoms, at times accompanied by some non-protist groups (like combining green algae with plants; e.g., see Cavalier-Smith, 1981, 1983; Sta- robogatov, 1984). Personally, along with Barnes (1984), Margulis & Schwartz (1982), and others, I believe that one kingdom of protists is adequate, as are four for the Eukaryota overall. But I (Corliss, 1984b) disperse groups of protists (the 45 phyla I recognize) among 18 supraphyletic assemblages, without pro- posing formal names for the latter.

How MANY KINGDOMS, THEN, AND WHY?

In this brief historical overview of the situation, space considerations pre- clude detailed consideration or attempted resolution of the multitude of "on- going" problems involved-nor would such be appropriate. It seems to me that a tentative answer to the overall question, at least, depends on definitions, and, of course, on proper use of a constellation of characters, without neglect of those available through the use of modern microscopical techniques. If one were a zoologist, for example, one ought first to have an intuitive "feel" for what an animal is (not ignoring pertinent findings from any field of inquiry); then, he or she ought to be able to verbalize it without fuzziness, circular reasoning, weak rationalizations, etc. By that time, one might be in a position to judge whether other assemblages of seemingly different eukaryotic organisms should really be considered taxonomically distinct or not at such a very high level as kingdom.

I should thus like to offer here my own succinct diagnoses of the four eukaryotic kingdoms that I believe are sufficient to embrace all groups of organisms above the evolutionary level of the prokaryotes. The characters selected for comparative usage stress major uniquenesses, emphasizing the presence rather than absence of a structure or function. At the end of each diagnosis, I have added a note about the included taxa and about the numbers of species described. Practically all of my data have been gleaned from the literature, and none of the kingdoms that I espouse has been created by me. The most controversial, obviously, is the Protista, from its very name to its internal composition. The neo-Haeckelian view of it that I hold, however, is

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supported by data and studies too numerous to cite here individually (but see especially Corliss, 1984b).

I. Kingdom ANIMALIA Linnaeus, 1753

Eukaryotic organisms without cell walls, with more than one type or kind of tissue, and exhibiting a heterotrophic (primarily phagotrophic) mode of nutrition. Species assignable here are commonly macroscopic in size and always multicellular, demonstrating the most highly differentiated organization at the tissue and organ level, and, almost without exception, showing complex em- bryological development during ontogeny, with inclusion of identifiable blas- tula and gastrula stages. Bilateral symmetry is very commonly exhibited. In the great majority of animals studied to date, gap junctions have been found to be universally present (although none in sponges and certain cnidarians, apparently3) between cells of tissues. Mitochondrial cristae are flattened or plate-like, with the principal exception in cells of the adrenal cortex of vertebrates. Lysine is not synthesized, but is an essential dietary requirement. Ga- metic meiosis is the rule. With relatively rare exception, by groups, animals are motile.

Some 1,500,000 valid species of animals, fossil and contemporary, have been recorded to date, and it is claimed (e.g., see Mayr, 1982) that roughly 10,000 new forms are described annually. The kingdom comprises some three dozen groups at the level of phylum, many classes, and nearly 500 orders, with invertebrate animals far outnumbering the more highly evolved vertebrates.

II. Kingdom PLANTAE Linnaeus, 1753

Eukaryotic organisms with cell walls composed of cellulose, with more than one type or kind of tissue, and exhibiting an autotrophic (phototrophic with chlorophylls a and b) mode of nutrition unless, in rare cases, chloroplasts have been secondarily lost. Species assignable here are commonly macroscopic in size and are always multicellular and vascular (except for the bryophytes), demonstrating a high degree of organization at the tissue level (nearly universally possessing roots, stems, and leaves). Plants typically show a regular alter- nation of haploid and diploid generations (the first is the gametophyte, the second is the sporophyte). In plant cells, the plastids are surrounded by two membranes only. Mitochondrial cristae are flattened or plate-like. The diamino-pimelic acid pathway is used in lysine synthesis. Sporic meiosis is the rule. The great majority of plants have become adapted to a sedentary terrestrial life, with vegetative or trophic forms therefore not independently motile.

Nearly 500,000 species of plants (minus "algae" now, of course), fossil and contemporary, have been described, with many new forms recorded annually.

3 Very recently (e.g., see Mackie et al., 1984) the evidence has grown nearly indisputable that certain "lower" animal groups are surely without gap junctions, as we recognize these ultrastruc- tures in "higher" animals. Included are the sponges (Porifera) and the cnidarian classes Anthozoa and Scyphozoa. The possible evolutionary significance of this is important but beyond consideration in the present paper.

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The number of phyla (or divisions) assignable to this kingdom varies with the author: from two to nine have been proposed, also with considerable differences in numbers of included classes and orders.

III. Kingdom FUNGI Linnaeus, 1753

Eukaryotic organisms with chitinous cell walls, a mycelial organization of vegetative cells functionally not representing more than a single kind of tissue, and exhibiting an exclusively osmotrophic type of heterotrophic (i.e., non- photosynthetic) nutrition. Species assignable here are often macroscopic in size and always multicellular (unless secondarily reduced to unicellularity, such as some yeasts) at some stage in the life cycle. The tubular filamentous or hyphal (coenocytic or septate) organization of fungi commonly results in production of a quite complex thallus or mycelium, but it never reaches a stage of differ- entiation clearly recognizable as composed of multiple tissues; and there are no vascular fungi. Vegetative stages are uniquely haploid and dikaryotic. Mi- tochondrial cristae are flattened or plate-like, and the Golgi cisternae are not stacked. The amino-adipic acid pathway is used in lysine synthesis. Zygotic meiosis is the rule. Spores are commonly involved in both sexual and asexual reproduction. Without pseudopodia, flagella, or cilia (or even centrioles) at any stage of the life cycle, true fungi are only passively motile.

Some 100,000 species of ("higher") fungi, fossil (rare) and contemporary, have been described. (The so-called "lower" or zoosporic aquatic fungi-not possessing the constellation of characters just enumerated-are removed to my kingdom Protista.) Fewer than half a dozen phyla comprise the kingdom Fun- gi, with several classes and quite a few orders recognized.

IV. Kingdom PROTISTA Haeckel, 1866

Eukaryotic organisms with no more than one tissue at most. In fact, species assignable here are predominantly unicellular in organization and microscopic in size. The relatively few syncytial, coenocytic, coenobial, or multicellular forms (generally appearing as filaments, colonies, coenobia, or thalli) are still without organization into multiple tissue types (although this remains a controversial point in the opinion of some phycologists). Macroscopic sizes are reached among species of a few groups (consider especially the brown algae), but clearly, functionally differentiated tissue stages are, again, absent; and there are no truly vascular forms. Motile species (often biflagellated or multi- ciliated or with pseudopodia at some stage in the life cycle) are considerably more numerous and more widespread throughout the contained taxa than non- motile species. Cysts or spores are common in many groups. Protists as a group exhibit all modes of nutrition, with both phototrophic (using various chlorophylls) and heterotrophic (phagotrophic, pinocytotic, osmotrophic) forms common. Both intra- and extra-cellular elaborations (organellar, skeletal, etc.) can show a great complexity. Mitochondrial cristae are tubular or vesicular or lamellar (flattened) or discoidal. Either the amino-adipic or diamino-pimelic acid pathway is used when lysine is synthesized. Mitotic mechanisms are diverse; and amitotic divisions occur as well. Nuclei are haploid, diploid, or

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polyploid; and the cells in one group are basically heterokaryotic. Meiosis-if or when it occurs-may be gametic, zygotic, or sporic.

Of a difficult-to-determine total number of species described, extinct and extant, some 120,000 may be tentatively considered valid and acceptable, with another 80,000 (mostly fossil "forams," actinopods, desmids, and especially diatoms) highly questionable, but many tens of thousands of additional distinct

species of all sorts remain to be discovered and/or properly described. Em- braced by this evolutionarily plastic kingdom are the superficial assemblages conventionally called "algae," "protozoa," and "lower fungi": I propose to

reassign or regroup all such species into some 45 phylogenetically diverse and

taxonomically distinct phyla (see Corliss, 1984b, and the Appendix included at the end of this paper).

In summary, after consideration of the evolutionary diversity of the biotic world, on the one hand, and the salient functional and anatomical features of

comparative systematic value, as they are to be found distributed among the

major groups of organisms, on the other, we can, without compromising stan- dards in the least, find value in the following taxonomic realignments from the old long-prevailing two-kingdom system:

(1) Complete separation of prokaryotes-the bacteria sensu lato (number- ing <5,000 species properly described)-from all other organisms, the eukaryotes. (No one seems to dispute this, if we ignore the phycologists' persistent claim to the cyanobacteria-as "blue-green algae"-and to Prochloron.)

(2) Retention of plant and animal kingdoms, but redefined, with tissue the issue, along with complex organizational, functional, and developmental characteristics not revealed in the other eukaryotic groups; that is, the degree and kind of cellular organization is significantly different in all four eukaryotic kingdoms.

(3) Recognition, long overdue, of the (higher) Fungi as a kingdom certainly separate from the plants.

(4) Acceptance of the phylogenetic-high-level-taxonomic integrity of the

protists as an independent kingdom, appreciating their role in the evolutionary experiments leading to the origin of the three other eukaroytic kingdoms and

recognizing the need to abolish such formal taxonomic units as the still widely conventionally maintained "Protozoa" and "Algae" and "Lower Fungi."

LITERATURE CITED

BARNES, R. S. K., ed. 1984. A Synoptic Classification of Living Organisms. Blackwell Scientific

Publications, Oxford and Sinauer Associates, Sunderland, Massachusetts. 273 pp. CAVALIER-SMITH, T. 1981. Eukaryote kingdoms: seven or nine? BioSystems, 14: 461-481.

1983. A 6-kingdom classification and a unified phylogeny. In Schenk, H. E. A. & Schwemmler, W., eds., Endocytobiology II: Intracellular Space as Oligogenetic Ecosystem, Walter de

Gruyter, Berlin and New York, pp. 1027-1034. COPELAND, H. F. 1956. The Classification of Lower Organisms. Pacific Books, Palo Alto, Cal-

ifornia. 302 pp. CORLISS, J. 0. 1978. A salute to fifty-four great microscopists of the past: a pictorial footnote to

the history of protozoology. Part I. Trans. Am. Microsc. Soc., 97: 419-458. 1979. A salute to fifty-four great microscopists of the past: a pictorial footnote to the history

of protozoology. Part II. Trans. Am. Microsc. Soc., 98: 26-58. 1983a. A puddle of protists: there's more to life than animals and plants. The Sciences, 23(3):

34-39.

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1983b. Consequences of creating new kingdoms of organisms. BioScience, 33: 314-318. 1984a. The kingdoms of organisms-from a zoologist's viewpoint. (Abstr.) Am. Zool., 24: 81A. 1984b. The kingdom PROTISTA and its 45 phyla. BioSystems, 17: 87-126.

DODGE, J. D. 1979. The phytoflagellates: fine structure and phylogeny. In Levandowsky, M. & Hutner, S. H., eds., Biochemistry and Physiology of Protozoa, Vol. 1, 2nd ed., Academic Press, New York and London, pp. 7-57.

DODSON, E. 0. 1971. The kingdoms of organisms. Syst. Zool., 20: 265-281. JEFFREY, C. 1971. Thallophytes and kingdoms-a critique. Kew Bull., 25: 291-299.

1982. Kingdoms, codes and classification. Kew Bull., 37: 403-416. LEEDALE, G. F. 1974. How many are the kingdoms of organisms? Taxon, 23: 261-270. MACKIE, G. O., ANDERSON, P. A. V. & SINGLA, C. L. 1984. Apparent absence of gap junctions

in two classes of Cnidaria. Biol. Bull. (Woods Hole), 167: 120-123. MARGULIS, L. 1970. Origin of Eukaryotic Cells. Yale University Press, New Haven. 349 pp.

1974. The classification and evolution of prokaryotes and eukaryotes. In King, R. C., ed., Handbook of Genetics, Vol. 1, Plenum Press, New York, pp. 1-41.

MARGULIS, L. & SCHWARTZ, K. V. 1982. Five Kingdoms: An Illustrated Guide to the Phyla of Life on Earth. W. H. Freeman, San Francisco. 339 pp.

MAYR, E. 1982. The Growth of Biological Thought: Diversity, Evolution, and Inheritance. Belknap Press of Harvard University Press, Cambridge, Massachusetts and London. 974 pp.

PARKER, S. P., ed. 1982. Synopsis and Classification of Living Organisms. 2 vols. McGraw-Hill, New York. 2,398 pp.

SLEIGH, M. A. 1979. Radiation of the eukaryote Protista. In House, M. R., ed., The Origin of Major Invertebrate Groups (Systematic Association Special Vol. 12), Academic Press, New York and London, pp. 23-54.

STACKEBRANDT, E. & WOESE, C. R. 1984. The phylogeny of prokaryotes. Microbiol. Sci., 1: 117- 122.

STANIER, R. Y. & VAN NIEL, C. B. 1962. The concept of a bacterium. Arch. Microbiol., 42: 17-35.

STAROBOGATOV, Y. I. 1984. [How many kingdoms are in nature?] Zndniye-s'la, No. 689(11): 23- 26. (In Russian)

STEWART, K. D. & MATTOX, K. 1975. Comparative cytology, evolution and classification of the green algae with some consideration of the origin of other organisms with chlorophylls a and b. Bot. Rev., 41: 104-135.

1980. Phylogeny of phytoflagellates. In Cox, E. R., ed., Phytoflagellates, Elsevier North- Holland, New York, pp. 433-462.

TAYLOR, F. J. R. 1978. Problems in the development of an explicit hypothetical phylogeny of the lower eukaryotes. BioSystems, 10: 67-89.

WHITTAKER, R. H. 1969. New concepts of kingdoms of organisms. Science, 163: 150-160. 1977. Broad classification: the kingdoms and the protozoans. In Kreier, J. P., ed., Parasitic

Protozoa, Vol. 1, Taxonomy, Kinetoplastids, and Flagellates of Fish, Academic Press, New York and London, pp. 1-34.

WHITTAKER, R. H. & MARGULIS, L. 1978. Protist classification and kingdoms of organisms. BioSystems, 10: 3-18.

WOESE, C. R. 1981. Archaebacteria. Sci. Am., 244: 98-122. WOESE, C. R. & Fox, G. E. 1977. Phylogenetic structure of the prokaryotic domain: the primary

kingdoms. Proc. Natl. Acad. Sci. U.S.A., 74: 5088-5090.

APPENDIX I

Because of the interest of many of the readership in protozoology and phy- cology, a summary is appended of my recent taxonomic-nomenclatural ar- rangement of the top-level groups comprising the kingdom PROTISTA Haeck- el, 1866 (see Corliss, 1984b, and particularly table 5 of that work). The names in italics, purposely given in their informal vernacular form, represent the 18 supraphyletic assemblages that I recognize. The latinized names, in roman type and accompanied by authorship and date of latter, are generally those of

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the phyla I am suggesting as probably appropriate for acceptance. However, I have proposed that only 45 of these phyla are likely to be most certain of defensible independent phyletic status. Thus, the following 10 names, considered to be associated with groups of highly uncertain high-level standing, may be more or less "ignored," being included here only for sake of completeness and beyond discussion in the present paper: Bicosoecidea, Heterochloridea, Raphidophyceae, Ebriidea, Ellobiophyceae, Acritarcha, Perkinsida, Actino- myxidea, Marteiliidea, Paramyxidea.

Rhizopods Karyoblastea Margulis, 1974 Amoebozoa Liihe, 1913 Acrasia Van Tieghem, 1880

Eumycetozoa Zopf, 1885

Plasmodiophorea Zopf, 1885 Granuloreticulosa De Saedeleer, 1934 (Incert. sed.: Xenophyophora Schulze, 1904)

Mastigomycetes Hyphochytridiomycota Sparrow, 1959

Oomycota Winter, 1879 (Incert. sed.: Chytridiomycota Sparrow, 1959)

Chlorobionts

Chlorophyta Pascher, 1914

Prasinophyta Christensen, 1962

Conjugatophyta Engler, 1892

Charophyta Rabenhorst, 1863 (Incert. sed.: Glaucophyta Bohlin, 1901)

Euglenozoa Euglenophyta Pascher, 1931

Kinetoplastidea Honigberg, 1963 (Incert. sed.: Pseudociliata Corliss &

Lipscomb, 1982)

Rhodophytes Rhodophyta Rabenhorst, 1863

Cryptomonads Cryptophyta Pascher, 1914

Choanoflagellates Choanoflagellata Kent, 1880

Chromobionts

Chrysophyta Pascher, 1914

Haptophyta Christensen, 1962

Bacillariophyta Engler & Gild, 1924

Xanthophyta Allorge in Fritsch, 1935

Eustigmatophyta Hibberd & Leedale, 1970

Phaeophyta Kjellman, 1891 (Incert. sed.: Proteromonadea Grasse in

Grass6, 1952 Bicosoecidea Grass6 & De-

flandre in Grasse, 1952 Heterochloridea Pascher,

1912

Raphidophyceae Chadefaud, 1950)

Labyrinthomorphs Labyrinthulea Cienkowski, 1867

Thraustochytriacea Sparrow, 1943

Polymastigotes Metamonadea Grasse in Grasse, 1952 Parabasalia Honigberg, 1973

Paraflagellates Opalinata Wenyon, 1926

Actinopods Heliozoa Haeckel, 1866

Taxopoda Fol, 1883 Acantharia Haeckel, 1879

Polycystina Ehrenberg, 1839 Phaeodaria Haeckel, 1879

Dinoflagellates Peridinea Ehrenberg, 1830

Syndinea Chatton, 1920 (Incert. sed.: Ebriidea Deflandre in Grasse,

1952

Ellobiophyceae Loeblich III, 1970

Acritarcha Evitt, 1963) Ciliates

Ciliophora Doflein, 1901

Sporozoa Sporozoa Leuckart, 1879 (Incert. sed.: Perkinsida Levine, 1978)

Microsporidia Microsporidia Balbiani, 1882

Haplosporidia Haplosporidia Caullery & Mesnil, 1899

Myxosporidia Myxosporidia Biitschli, 1881 (Incert. sed.: Actinomyxidea Stolc, 1899

Marteiliidea Desportes &

Ginsburger-Vogel, 1977

Paramyxidea Chatton, 1911)

10



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The Kingdoms of Organisms: From a Microscopist's Point of View