9 9SZ6S9EO LOLI € SEI OLNOYOL JO ALISYSAINN AMVAB ADO1OOZ See a - = 2 . ‘in ets with ‘und Pom | oa University of Toronto - 7 eis * ay : *, - | » “al Z eS : ‘ : 7 ey i ; ’ 9 las ' ra: a i wit ' p> ew 4 es $6 _ wo a iit aie aed Fo ae > a «= he ie aen cis - oi oe a yt Be ee ‘ eo 2 ew. 3 eee 2 : af i .* ~ . ’ A TREATISE ON ZOOLOGY Demy 8vo, Cloth, price 15s. net each ; or in Paper Covers, price 12s. 6d. net each. VOLUMES READY Part I. (First Fascicle) INTRODUCTION AND PROTOZOA. By Sir Ray LanxesteEr, K.C.B., F.R.S. ; Prof. S. J. Hickson, M.A., F.R.S.; F. W. GAMBLE, D.Se., F.R.S.; A. Wiiisy, M.A., D.Sc., F.BS.5 gow LisTeR, F.R.S.; H. M. Woopcock, D.Se.; and the late Prof. WELDON. Part I. (Second Fascicle) INTRODUCTION AND PROTOZOA. By J. B. Farmer, D.Sc., M.A., F.R.S. ; J. J. LISTER, F.R.S.; E. A. MINCHIN, M.A. ; and §. J. Hickson, F.R.S. Part Il. THE PORIFERA AND COELENTERA. By Sir Ray LANKESTER, K.C.B., F.R.S.; E. A. MINCHIN, M.A.; G. HERBERT FOWLER, B.A., Ph.D. ; and GILBERT C. BourRNE, M.A. Part III. THE ECHINODERMA. By F. A. Baruer, M.A., assisted by J. W. Grecory, D.Se., and E. S. GoopRIcH, M.A. Part IV. THE PLATYHELMIA, THE MESOZOA, and THE NEMERTINI. By Prof. Beyuam, D.Se. Part V. MOLLUSCA. By Dr. Patt PILSENEER. Part VII. CRUSTACEA. By W. T. Catman. Part IX. VERTEBRATA CRANIATA. By E. 8. GoopRIcH, F.R.S. A TREATISE ON ZOOLOGY EDITED BY Sir RAY LANKESTER K.O.B., M.A., LLD., FBS. HONORARY FELLOW OF EXETER COLLEGE, OXFORD; CORRESPONDENT OF THE INSTITUTE OF FRANCE, LATE DIRECTOR OF THE NATURAL HISTORY DEPARTMENTS OF THE BRITISH MUSEUM Part [| INTRODUCTION AND PROTOZOA FIRST FASCICLE BY §. J. HICKSON, F.R.S. PROFESSOR OF ZOOLOGY, VICTORIA UNIVERSITY OF MANCHESTER J. J. LISTER, FERS. FELLOW OF ST. JOHN’S COLLEGE, CAMBRIDGE FW. GAMBLE, D.Sig oc R.S. ASSISTANT DIRECTOR OF THE ZOOLOGICAL LABORATORIES, AND LECTURER IN ZOOLOGY, UNIVERSITY OF MANCHESTER, A. WILLEY, M.A., D.Sc., F.B.S. DIRECTOR OF COLOMBO MUSEUM, CEYLON H. M. WOODCOCK, D.Sc. {/ ASSISTANT TO THE PROFESSOR OF PROTOZOOLOGY IN THE UNIVERSITY OF LONDON , Tue Late W. F. R. WELDON, F.RB.S. Lf cS . LINACRE PROFESSOR OF COMPARATIVE ANATOMY, OXFORD AND ae E. RAY LANKESTER, K.C.B,, FURS. f 4 | wy! LONDON ADAM AND CHARLES BLACK \ 1909 | ‘ AGENTS America . . THe MACMILLAN COMPANY 64 & 66 Firra Avenue, New York AvusTraALasiA THe Oxrorp UNiversity Press 205 Fuixpers LANE, MELBOURNE Canapa . . THe Macmittan Company or Canapa, Lip. 27 Ricumonp Street West, Toronto Inpia. . « Macmtttan & Company, Lrp. MacMILLAN Buitpina, BoMBAY 309 Bow Bazaar Streer, Carcurta PREFACE THE two fascicles of the first part of this treatise give a more complete account of the Protozoa than is to be found in any similar work hitherto published. Especial attention has been given to the treatment of those groups— the Sporozoa, Flagellata, and Heemoflagellata—which have recently acquired so much importance in consequence of the discovery that some of their constituent members are the causes of important. diseases in man and animals. E. RAY LANKESTER. December 1908. CONTENTS INTRODUCTION . CHAPTER I.—PROTOZOA Section A.—THE PROTEOMYXA B.—THE HELIOZOA . C.—THE MYCETOZOA D.—THE LoBosa E.—THE RADIOLARIA ~F.—THE MASTIGOPHORA . G.—THr HAEMOFLAGELLATES AND ALLIED FORMS . APPENDIX A.—CHLAMYDOMYXA AND LABYRINTHULA . B.—THE XENOPHYOPHORIDAE bp) INDEX vu PAGE A TREATISE ON ZOOLOGY. INTRODUCTION.! THERE are certain matters which require brief treatment by way of introduction to the present treatise on Zoology. The first concerns the limitation of the subject-matter indicated by the term “ Zoology,” requiring a statement of what living things are here considered as animals and what are excluded from that title. The second concerns the grouping of animals in large series corresponding to the indications afforded by their structure as to their genetic affinities. The method adopted in the present work has been to take large divisions of the Animal series such as are often called “sub-kingdoms” or “phyla” (or in some instances less comprehensive divisions) one by one for systematic description and for more detailed enumeration and justification of the classes, orders, and families recognised than is usual in handbooks of Zoology. These large divisions have been assigned for treatment to separate authors, and in each case the author has given a description of the characters which justify the recognition of the group which he treats as an independent series; to this he has added a more extended discussion of the range of variety in the structure of the forms held to be reasonably considered as members of the series. A special chapter written by me forms the introduction to volume ii. of this work. It may be regarded as a continuation of the present chapter, and treats of the division of the higher grade of animals, which is called the Metazoa (the lower being the Protozoa), into two branches, the “ Parazoa” and the ‘“ Enterozoa.” It is, however, chiefly occupied with a discussion of the division of the Enterozoa into two grades of higher and lower structural complexity, which are designated respectively the ‘‘ Enterocoela ” and “Coelomocoela.” The chief phyla or large branches of the animal pedigree are there enumerated, whilst each is subsequently treated by independent authors. In the present introductory chapter I have therefore to consider, besides the question as to what distinctions separate animals from 1 By Sir Ray Lankester, K.C.B. 4 x INTRODUCTION other living things, the facts which render it necessary to recognise two great primary grades of animals—a lower called the Protozoa and a higher called the Metazoa. A. THE DIVIDING-LINE BETWEEN PLANTS AND ANIMALS. Living things—Bionta—are without difficulty, and by the general agreement of both skilled naturalists and the observant layman, divided into two greatly differing groups or series, the animals or Zoa and the plants or Phyta, and into those two great groups only. The study of the one series is called Zoology, and of the other Phytology, or more usually Botany. It is easy to lay down certain general propositions by which nearly all animals are distinguished from nearly all plants. The distinctions which can be thus indicated all arise from one great difference in the chemical activity of the living substance of an animal as compared with that of a plant. Although the living substance of both animals and plants, to which Hugo von Mohl gave the name Protoplasm, appears in both series in the form of nucleated corpuscles called cells, and although the formal appearances and the range of chemical activities exhibited both by the general protoplasm and by the nuclear structures of the cells of animals and plants are practically identical, yet there is a predominant difference in the habitual exhibition of their activities which separates animals from plants, and has determined the difference of form and activity characteristic of the living things assigned to either of the two groups. Living protoplasm, whether of animal or plant, undergoes (when the processes of life are not, as they may be for a short or for a very extended period, suspended) constant chemical change, requiring the access of free oxygen to the protoplasm and the consequent oxydation of some of its material—which becomes “wasted” or lost and carried away by diffusion from the living protoplasm. This loss has to be replaced, and the process by which it is replaced is “nutrition”; the material taken by a living thing for the purposes of nutrition is its “food.” The result of nutrition is not limited to the repair of loss in the living thing, but is for a part or the whole of its existence in excess of the loss; so that increase of the bulk of the living material or “growth” is a result. The elements carbon, hydrogen, oxygen, and nitrogen, combined to form molecules of the highest degree of complexity, are the essential constituents of living material. It is these that are oxydised and wasted and pass from the living thing during life: it is these which have to be replaced. Animals are unable to assimilate, that is, to utilise as food, the simpler chemical compounds of carbon or of nitrogen. They can only take their nitrogen from food which is in the elaborate form of INTRODUCTION xi combination which is called a proteid ; they can only take their carbon either from a proteid or from a carbohydrate or a hydrocarbon. These elaborate compounds only occur in the bodies of other animals or of plants. Hence animals absolutely depend for their food on other living things. Plants, on the contrary, are (with certain exceptions) able to take up as food the compounds of carbon and of nitrogen which may be called the stable or resting condition of those elements—namely, the simple oxide of carbon—carbonic acid gas and the simple compound of nitrogen with hydrogen which is called ammonia, or the oxide of nitrogen which forms nitrates. This “food” of plants is diffused throughout the earth’s surface in air and water; hence they need to expose a large absorbing surface to those media; hence their branches and leaves spread in tree- like form to the air or to the water, whilst their roots are spread to the water contained in the soil. Their food is ever moving and flowing around them: they have neither to move in search of it nor to seize it. Hence the majority of plants are fixed and find safety and protection in stability. Animals, on the other hand, have to obtain their food from the scattered, solid, separate bodies of plants or of other animals. They have to move in search of it, they have to seize it when found, and they have to act chemically on the solid or viscous body or fragment of their prey so-as to dis- solve it and to enable the dissolved material containing the precious carbon and nitrogen in a high state of chemical combination to diffuse into their living substance and there be further assimilated and built up into the material of protoplasm. Jor these purposes animals possess structures enabling them to move more or less rapidly, and others enabling them to seize or grasp. Further, and of even more fundamental a character as determining their whole shape and organisation, they possess (with rare and_ intelligible exceptions) an aperture, the mouth, leading into a relatively extensive cavity, the gut, into which the solid or viscous mass of food is intro- duced, and when there is chemically dissolved or “ digested.” The obvious and predominant difference in the make and _ habit of plants as compared with animals is thus connected with the very great and definite difference in the nature of the food of the two groups. These statements are true in a general way, but require qualification. In the first place, we find it necessary to regard as genetically part of the great Plant series many organisms which are not able to procure their carbon from carbonic acid nor their nitro- gen from ammonia. Only the green plants are able to perform this constructive feat. The protoplasm of the more superficial cells of green plants contains corpuscles impregnated with a transparent green matter known as chlorophyll. In the presence of and in virtue of the physical action of sunlight screened by their chloro- xii INTRODUCTION phyll, the protoplasm of these cells has the property of decompos- ing carbonic acid, liberating free oxygen, and combining the carbon with hydrogen and oxygen to form starch. ‘This is the critical step in the interaction of chemical elements on the earth’s surface, by which life is at present determined. Were there no assimilation of carbon from carbonic acid to form starch—by the green plants— the whole fabric of the living world would tumble to the ground—in truth, become mineralised. All living matter breaks down, within a short space of hours or days, to the resting or mineral condition of carbonic acid and ammonia (or nitrates). Were the building-up process, the raising to higher potentiality, not incessantly performed by green plants—a power which chlorophyll and chlorophyll alone confers on them—all carbon must pass from the reach of the organic vorld and living matter come to an abrupt end. And this is equally true of nitrogen. The nitrogen present in living protoplasm tends inevitably to ‘the stable inert condition—as a nitrate, as ammonia, or as the pure dissociated atmospheric gas, It is only by a subtle chemical process which occurs in the green plant—as a result of and in connection with the fixation of carbon as starch—that nitrogen taken up in water by the roots of the plant as nitrate and as ammonia is brought into combination as part of an “organic” compound or molecule. Thus in the ultimate history of the chemistry of living things the animal depends for its necessary food—proteids, carbohydrates, and hydrocarbons—on chlorophyll, the ‘“leaf-green” of green plants. Vegetarian animals swallow and digest these substances built up by plants ; carnivorous animals swallow and digest animals which have already profited by the work of the green plant. No animal can take up even a fraction of a grain of carbon or nitrogen from a stomachful of carbonates, nitrates, and ammonia. There are, however, as exceptions plants which are devoid of chlorophyll and depend upon the results of the constructive activity of other plants and of animals, just as per contra there are ex- ceptional parasitic animals which have no mouths or gut and live in the diffusible nutritive juices elaborated by other animals, which they absorb by the surface of their bodies. The chemical life of those plants which are devoid of chlorophyll—the fungi, the bacteria, and a few others—may be considered as corresponding in character to that of those tissues or cell-groups of green plants which lie within the green plant and are devoid themselves of chlorophyll. Both these tissues and the autonomous fungi and the saprophytes depend for their food on the products supplied to them by the chlorophyll-holding cells of green plants. ‘There are minute filamentous and rod-like plants devoid of chlorophyll (Bacteria and others) which can take their carbon as tartaric acid and their nitrogen as ammonia. It is probable that all such non- INTRODUCTION xiii chlorophylligerous plants must be regarded as derived from chloro- phyll-bearing ancestors—by adaptation to a food already somewhat raised by other organisms above the lowest stage of carbon- combination. Again, there are amongst the most highly developed flowering plants examples here and there of the exceptional and special development of stomach-like organs with mouth-like openings into which insects are attracted, and when once entrapped are held either by the actual movement of a grasping organ or by other mechanical apparatus, and are digested by chemical secretions identical in character with those of the animal stomach, the digested product being absorbed and serving to nourish the plant. Such cases, whilst they demonstrate in a most striking way the essential identity of the faculties of the living protoplasm of plant and animal, do not invalidate the fundamental proposition, that plants are a series of organisms which have developed their distinctive form and structure as feeders on the diffused carbonic acid, ammonia, and nitrates of the circumambient medium; whilst animals are a series which have developed their distinctive form and structure as feeders on scattered—often elusive—live or dead bodies or solid particles of other animals or of plants, that form being essentially a locomotive sac with a mouth.. Amongst the larger animals, those visible to the naked eye, there are few exceptions to this rule. Such exceptions are found in the obviously exceptional and therefore aberrant internal parasites which require no mouth nor digestive sac. But there are a few, very rare cases of small aquatic animals which are provided with chlorophyll-corpuscles and obtain a part (in one case, the worm Convoluta, the whole) of their nutriment in the same way as does the green plant, namely, in virtue of the assimilation of carbon from carbonic acid in the chlorophyll- bearing tissue when under the influence of sunlight. The chlorophyll-bearing cells of the worm Convoluta and of many Anthozoa have been shown to be unicellular parasites which have established the closest relationship to their hosts. But it is by no means demonstrated that the chlorophyll-corpuscles of Spongilla and of Hydra are parasitic in origin! The fact that they are not chlorophyll-bearing cells, but simple non-nucleated corpuscles with a cortex impregnated with chlorophyll precisely comparable to the chlorophyll corpuscles of green plants, does not permit us to consider them as parasites which have effected a lodgment and association with Spongilla and Hydra with any more reason than we can adduce for so regarding the similar ‘corpuscles in green plants. The view has been seriously advanced that the latter are, 1 See on this subject my memoir on ‘‘ The Chlorophyll-corpuseles and Amyloid Deposits of Spongilla and Hydra” in vol. xxii. (1882) of the Quart. Journal of Microsc. Science. Xiv INTRODUCTION in fact, also parasites. This may prove eventually to be susceptible of something like demonstration, but in the meantime we must ask where the limit to this assumption that chlorophyll is of parasitic origin is to be placed. It cannot be that all chlorophyll—even that observed in all uni- cellular plants and animals—is to be regarded as “parasitic.” And if we are once able to distinguish certain independent unicellular organisms which actually manufacture chlorophyll within them- selves by the activity of their own protoplasm, we shall be able to study the steps of that process and to judge as to whether the protoplasm of the green cells of green plants and of the freshwater sponge and of the green Hydra do or do not form chlorophyll plastids in the same way and in virtue of the same protoplasmic capacity as do minute unicellular algae. There is no reason, a priori, for refusing to ascribe to a tissue- cell of a Sponge or a Hydra the same capacity to form a chemical deposit of any kind which a free unicellular organism possesses. Unfortunately this is not a case in which the simple test of observa- tion can be applied, so that the question as to whether the tissue- cell does construct a chlorophyll-corpuscle or does not can be settled by inspection. ‘The intricacies of structure and growth are in this matter such as to render direct observation difficult and illusive. Whilst there are, then, exceptional cases in both plants and animals as to the great nutritional distinction between the two series, it is comparatively easy in all excepting the very lowest forms to satisfy ourselves that the departures from the rule are specialised derivatives from the main series. The colourless or greenless plants are descended from green chlorophylligerous ancestors ; mouthless, gutless animals are descended from mouth- bearing, gut-hollow animals. When, however, we come to the very lowest unicellular micro- scopic forms of life, there is greater difficulty in assigning some of the minuter organisms to one side or the other, and to some extent our decision in the matter must depend on the theory we may provisionally adopt as to the nature of the earliest living material, which was the common ancestral matrix from which both the Plant series and the Animal series have developed. The real question in regard to such a theory is as to whether we find reason to suppose that the combination of carbon and nitrogen to build up proteid, and so protoplasm, required, in the earliest state of the earth’s surface, the action of sunlight and the chlorophyll screen. We must remember that, though these are now necessary for the purpose of raising carbon, and indirectly nitrogen, from the mineral resting state to the high elaboration of the organic mole- cule, yet it is, after all, living protoplasm which effects this marvel with their assistance ; and it seems (though possibly there are some pea er ere) BA INTRODUCTION Xv who would deny this) that it is protoplasm which has, so to speak, invented or produced chlorophyll. Accordingly, I incline to the view that chlorophyll as we now know it is a definitely later evolu- tion—an apparatus to which protoplasm attained, and as a conse- quence of that attainment we have the arborescent, filamentous, foliaceous, fixed series of living things called plants. But before protoplasm possessed chlorophyll it had a history. It had in the course of that history to develop the nucleus with its complex mechanism of chromosomes, and it had during that period to feed. The suggestion has been made long ago (see article ‘‘ Protozoa,” Ency. Brit., 6th edition), and appears to me not improbable, that by whatever steps of change that high complex of organic molecules which we call protoplasm—the physical basis of life—came into existence, it very probably fed in the first few eons of its existence on the masses of proteid-like material which, it may be supposed, were formed in no small quantity as antecedents to the final evolution of living matter. If this were the case, the mode of nutrition of the first living things must have been similar to that of animals and unlike that of plants. At a later stage chlorophyll was evolved, the decomposition of carbonic acid became possible, and the Plant series was started. In accordance with this conception, we must look for the representatives of the most primitive forms of life amongst the minute Protozoa, possessing the simplest methods of nourishing themselves by the digestion of already elaborated proteid. Such are the Mycetozoa, which digest dead organic material by contact, creeping in the form of naked plasmodia of many inches in area over organic débris; such, too, are the minute single cells of naked protoplasm taking in particles of proteid food by extemporised mouths and digesting them in the cell-body, whilst prehensile and motor organs are furnished by the extension of the cell-protoplasm in the form of lobose processes, radiating filaments, or single or double vibratile flagella. The earliest plants, the Protophyta, were, it seems most probable, derived from flagellate colony- building Protozoa (similar to the Volvocinez), which had, at first without discarding their animal-mode of nutrition (Zootrophic), acquired the faculty of manufacturing chlorophyll and supplementing their ingested nutriment by the decomposition of carbonic acid and the fixation of nitrogen (Mixotrophic). The step from this to a purely chlorophyll-given nutrition (Phytotrophic) was not a long one, and indeed occurs in the life-history of some of the Flagellata at the present day. With the establishment of pure Phytotrophic nutrition ensued the formation—by simple cell-division and element- ary variation of cell-aggregation—of filamentous green plants consist- ing of chains of cells in single series ; to these followed networks of xvi INTRODUCTION such chains, then growth and division of the still-connected cells in two and finally in three dimensions, producing first sheet-like and finally more solid structures, the constituent cells of which became variously differentiated and specialised. Those extremely minute, thread-like (Leptothrix, Spirillum), or rod-like (Bacillus) plants devoid of chlorophyll, which often break up without losing vitality into spherules or into granules of even ultramicroscopic tenuity, known as the Schizomycetes (or colloquially Bacteria), cannot be considered as primitive. Like the Fungi and many of the most highly organised plants, they have descended from chlorophyll-bearing forms, and have become adapted to a parasitic or saprophytic mode of nutrition whilst retaining the general characteristics of growth and form of their ancestors. The intimate connection of the Schizomycetes with the Oscillatoriz does not seem to admit of any doubt, and forms closely allied to them develop chlorophyll as well as peculiar blue and red pigmentary substances, the function of which is obscure but may be related to their modified nutritional processes. We are thus led to regard all the non-filamentous, non-chlorophylligerous microscopic forms which are not referable to the Schizomycetes or to the simpler Fungi as “Protozoa.” The debatable ground is limited to the chlorophyll-forming Flagellata, amongst which are some which, being devoid of mouth and at all periods of their growth incapable of zootrophic activity, are yet so closely allied in life-history and structure with truly zootrophic species that it is not possible to draw a sharp line and assign them definitely either to the Animal or to the Plant series. Such are the Volvocineans, which zoologists will probably for some time to come consider it desirable (as we do in the present treatise) to treat of in the description of the Animal series, whilst botanists will find it equally desirable to discuss them in connection with closely allied minute Plants. In view of these considerations, we consider the following groups of the simplest organisms as belonging to the Animal series, and as constituting a lowest “grade” of animal organisa- tion, to which the term Protozoa is applicable. The groups in question are given the title of “classes,” but it will readily be understood that it is not intended to imply by that term that they have any exact equivalence in the amount of divergence from one another to that which is presented by the “classes” of any one of the phyla of the Metazoa. Protrozoa.—Class 1, Proteomyxa; Class 2, Heliozoa; Class 3, Mycetozoa ; Class 4, Lobosa ; Class 5, Radiolaria ; Class 6, Mastigophora; Class 7, Sporozoa; Class 8, Ciliata ; Class 9, Acinetaria, INTRODUCTION xvii B. SEPARATION OF THE GRADE PROTOZOA FROM THE GRADE METAZOA. Formerly the name Protozoa was used for a sub-kingdom of the Animal Kingdom equivalent in value to other sub-kingdoms which were enumerated as the Coelentera, the Vermes, the Arthropoda, the Echinoderma, the Mollusca, and the Vertebrata. In its earlier use the great division ‘“‘ Protozoa” was made to include the Sponges, which we now assign to a divergent line of descent, the Parazoa, opposed to the main line, the Enterozoa, in the higher grade of animals called the Metazoa. The removal of the Sponges from association with the Protozoa is chiefly due to the initiative of Ernst Haeckel. By this step it became possible to give something like a definite characterisation of the Protozoa and to mark them off from all the higher animals. They are definitely characterised by the fact expressed in the English name Cell-animals (Plasti- dozoa), or less correctly unicellular animals, whilst all the higher animals or Metazoa (inclusive of the Sponges) are Tissue-animals (Histozoa). The fact indicated in these terms is that in Protozoa a single cell or a colony of equi-pollent cells is the organic “individual,” whilst in the Metazoa the “individual” is built up by cells which are differentiated into at least two layers or tissues, the cells of each tissue being of like value and origin with its fellow-cells of that tissue, but differing essentially in structure, function, and origin from the cells of the other tissue or tissues. ‘These statements will be found on critical examination to hold good in view of our present knowledge of both Protozoa and Metazoa. Most of the Protozoa are unicellular, and in those which form many-celled colonies, such as the Mycetozoa, some of the Radiolaria, Mastigophora, Ciliata, and Acinetaria, there is no tendency for those cells to differentiate into groups of cells of like structure and function to one another, but differing in structure and function from another group or groups present in the same colony. The only approach to an exception to this generalisation is found in the specialisation of a cell here and there in the colony as a reproductive cell; but, on the other hand, it is to be noted that any cell in the colony is potentially a reproductive cell, and there is no differentiation of a congeries or tissue of cells for reproductive pur- poses in the general plan of the colonial structure.’ It appears to be the fact that we do not know of any forms at present existing which furnish a transition from Protozoa to the Metazoa. There 1 Though the existence of at least two ‘‘tissues” in the Metazoa suffices to dis- tinguish them from all Protozoa, it may legitimately be contended that the congeries of cells forming the colony of certain Protozoa (e.g. Volvox) is rather of the nature of a ‘‘tissue” than of a merely loosely adherent association of cells which, as we see _in many Protozoan colonies, can and do separate freely and irregularly from such association. XVlii- INTRODUCTION have been descriptions of supposed independent organisms sug- gesting such intermediate character (Z’vrichoplax and others), but the true nature and history of these structures have not been placed on a definite basis, and do not really admit of discussion.. The nearest case of a transitional form appears to be the Choano- flagellate ‘‘Proterospongia” of Savile Kent, which has been observed on several different occasions from different localities. It combines in one colony “amoebocytes” and “choanocytes,” but it appears that the one form of cell develops into the other. It is certainly not unreasonable to regard Proterospongia as a step forward from the Choanoflagellata in the direction of the Parazoa. There is no instance of equally definite character tending to connect Protozoa of any class with the Enterozoa. Until recently it was possible to add to this distinction between Protozoa and Metazoa the very striking one that all Metazoa reproduce by means of fertilised egg-cells (as well as by other processes), such fertilised cells being the result of the union of specially developed egg-cells and sperm-cells. Conjugation of two cells similar to one another as a preparation to multiplication by fission was known and described in several Protozoa, but the special units, the static female egg-cell and the motile male “spermatozoid,” were unknown in Protozoa. The apparent exception to this pre- sented by some of the Volvocinean Flagellata was regarded as a reason for assigning these organisms to the pedigree or great series of Plants, thus removing them from association with the other Flagellata. In the Plant series, though many groups both among the highest and lowest do not present sexual reproductive elements under the typical forms of egg-cell and spermatozoid (antherozoid), yet some of the lowest and simplest, as well as some of the higher, plants do develop motile conjugating “male” cells, which seem to render the relegation of Volvox to the vegetable series a reasonable proceeding. Within the last decade, however, we have not only become acquainted among undoubted Protozoa with instances of the development of ‘ microgametes” or small conjugating cells, which are distinguished by their size from the larger egg-cells or “macrogametes” with which they fuse in order to form a fertilised “germ,” but we now know undoubted Protozoa which exhibit the breaking up of a parent male unicellular individual into a number of motile microgametes. These have the appearance and characteristics of the spermatozoa of higher animals, are developed from the parent male cell by the same steps as are spermatozoa from sperm-mother-cells, and proceed to fertilise the female macro- gametes in the same manner as occurs in the fertilisation of the egg-cell in Metazoa, The Coccidiidae among the Sporozoa and certain of the Haemo- flagellata are the Protozoa in which this phenomenon has been INTRODUCTION Bit carefully observed. It is identical in its essential features with the sexual reproductive phenomena of the colonial Flagellate, Volvox globator. Not only so, but the egg-cells and spermatozoa thus developed and uniting are identical in character with the egg-cells and antherozoids of a vast series of lower and higher plants, and with those of the whole series of Metazoa. A very important link in the genetic relationships of Plants and Animals is thus established. There is no occasion to suppose that they have independently developed the typical form of the male and the female reproductive particles. The plants have inherited this from the Protozoa which gave rise to the earliest chlorophylligerous, phytotrophic organisms. It is perhaps necessary to remark that further observation is necessary in these lowest forms as to the precise steps in the preparation of the nucleus and its chromatin in each of the conjugating gametes for the definite union of fertilisation. There is abundant evidence that it is of the same nature as that which occurs in the sexual cells of higher organisms, but in special details we may have to recognise some differences. C. SEPARATION OF THE CLASSES OF PROTOZOA INTO GRADES OF LOWER AND HIGHER STRUCTURE. The question as to whether the various classes of Protozoa are to be regarded as nine separately divergent lines of descent, starting from a common primitive ancestry not represented at the present time by any one of them, or whether some of them possess closer genetic relationship inter se than do others, is a very difficult one. It has been proposed at various times to seek for evidence of such closer affinity in the development of a cortical firmer layer of the cell-protoplasm (as in most Sporozoa and in the Ciliata), as opposed to the retention of the uniform viscid character of the protoplasm (Lankester, Ency. brit., article “ Protozoa”), and again it has been considered probable that all those forms which produce temporary lobose or filamentar extensions of the protoplasm, as locomotor or grasping organs, may have a genetic community of origin which separates them from those provided with either isolated flagella or with “cilia” of vibratile protoplasm. Some or other, however, of the forms which it is found necessary, on account of the affinities indicated by their life-histories and other details of structure, to class as Flagellata (Mastigophora) exhibit combinations of characters which render both these attempts at grouping unsatisfactory. We find Flagellata (see the section on this group) which produce extensive amoeboid processes, and yet possess a flagellum, whilst the majority have a distinctly corticate protoplasm. Among the Sporozoa (for which refer to the section on that group in the second fascicle of Part I. of this treatise), which are with these rare excep- tions strongly corticate, we find genera which produce lobe-like and XX INTRODUCTION pointed “pseudopodia” from their superficial protoplasm (Zygoco- metes and others). It seems that in any attempt at a phylogeny of the Protozoa we should have to treat the assemblage of forms now classed as Mastigophora (Flagellata) as a central group from which the other eight classes have been derived, whilst embracing in itself several specialised lines of descent, including that which has given rise to the primitive green plants. The indication of a higher and later elaboration of structure, as distinct from a lower and more primitive, by means of the classificatory artifice of “ grades,” has, however, been introduced in the present work by Professor Hickson in regard to the classes of Protozoa by a consideration of the cell-nucleus. The condition of this important structure justifies, he considers, the separation of the classes of Protozoa into a lower and a higher grade—the Homokaryota and the Heterokaryota—and it is not improbable that further study of the lower grade will lead to the subdivision of that assemblage into sub-grades. The history of the nucleus of the corpuscle of protoplasm, that corpuscle which it is customary to regard under the name of “the cell” as the unit of living structure, is at present absolutely un- known and altogether a matter of conjecture. It may perhaps be conceded as highly probable that the earliest protoplasm was with- out nucleus or differentiated nuclear material. It is a legitimate contention that such a substance should not be called ‘‘ protoplasm ” at all, since Hugo von Mohl invented this term to describe the viscid contents of a vegetable cell expressly including the nucleus a3 part of it. It was proposed some twenty-five years ago by Ed. van Beneden to call the earlier non-nucleated stage of living matter ‘“‘plasson,” and it seems to me by adopting this term we can preserve the word “ protoplasm” for its original use. At the same time it is important to avoid using the word “ protoplasm,” as is not unfrequently done, to signify the critical chemical body which undoubtedly is present in living protoplasm and is the apex of the pyramid or the top of the fountain, to which a variety of chemical bodies are leading and from which another series of chemical bodies are receding at every moment of the chemical activity of living protoplasm. Protoplasm is not a chemical body but a structure, and its nuclear particles, as well as its definitely formed nucleus consisting of chromatin and other constituents, are parts of it. It seems necessary to have a word by which to refer to the highest group of chemical molecules to which one set of chemical processes in the cell are always leading and from which another series are reced- ing. I proposed some years ago (Ency. Brit., article ‘ Zoology ”) to speak of this hypothetical body as ‘ plasmogen.” In the same way it is necessary to avoid the tendency which exists to employ the word “protoplasm” to describe cell-substance both when con- INTRODUCTION xxl sidered as apart from the nucleus and when actually existing in an unmanipulated simplest living thing without any nucleus or nuclear matter. We have seen that “ plasson” is the name which has been proposed for the latter; for the former the word “cytoplasm ” is frequently used, whilst ‘ nucleoplasm” is applied to that part of the cell-protoplasm which is the nucleus. The use of the word ‘cyto- plasm ” in this sense is certainly objectionable, as it signifies “ the cell-plasm” and is merely a synonym of “protoplasm.” It would be better to term the extra-nuclear substance of the protoplasmic corpuscle ‘ periplasm.” As a hypothesis we may assume that living matter was at one time in the condition of “ plasson,” though it has yet to be shown that “plasson” is in existence at all at the present day. The next hypothetical stage is the development in distinct granular form of the material which later became aggregated as a nucleus. We may apply the word “protoplasm” to this stage, with a qualifying adjective, ‘“konio-karyote” (powder-nucleated). This condition is known as actually existing in certain phases of the ciliate Protozoa (Trachelocerca), and possibly is to be recognised in some degenerate Protophyta and in some of the Proteomyxa (whether degenerate or archaic) amongst Protozoa. The third stage in the hypothetical development of protoplasm consists in the aggregation of the scattered nuclear granules to form one or more nuclei of definite structure and properties. Usually but one such nucleus is formed, but to cover the case of the existence of two or more similarly organised nuclei the term Homokaryote (proposed by Professor Hickson) may be used for this condition. The nucleus of the Homokaryote cell is in leading’ features of its structure identical with that of the tissue-cells of higher organisms. It consists of nuclear capsule, nuclear hyaloplasm, and of chromatin elements. The optical, chemical, and physiological analysis of the nuclei of Protozoa and Protophyta has not been extended to a sufficient number of instances, at present, to render it possible to trace the steps (if they are still traceable) by which the complete structure of the nucleus and its activity in cell-division were evolved. It is not yet clear whether there are among Protozoa and Proto- phyta any surviving simpler phases of the nucleus, or whether apparently primitive phases which are described are so interpreted owing to incomplete observation or, on the other hand, owe their simplicity to a degeneration from a more highly developed condition of the nucleus. It is, however, certain that there are cases amongst the Protozoa in which the structure and activity of the nucleus in cell-division conforms very closely to those of the tissue-cells of higher animals and plants, if not absolutely identical with them. There are, however, in certain Protozoa special modifications of the nuclear structure which have not yet been shown to occur in Xxil INTRODUCTION Metazoa, nor in plants. The most striking of these is the division of the nucleus in Ciliata and Acinetaria into two unequal and dissimilar portions, the mega-nucleus and the micro-nucleus, which appear to be the portions of the primary nucleus which preside over the somatic (the larger) and reproductive activities (the smaller) respectively. Professor Hickson has made use of this differentiation of the nucleus into two parts in order to establish a higher grade of the Protozoa—the Heterokaryota as distinguished from the Homokaryota. Amongst those forms, however, which are classed by him as Homokaryota, there are (as he recognises) certain forms amongst the Flagellata which also exhibit a differentiation and segregation of the nucleus, but with functions for the separated elements different from that shown in the Ciliata. This case is that of the formation of a separate nuclear body, the kineto-nucleus, in con- nection with, and apparently controlling the activities of, the large and powerful flagellum of certain flagellate forms (Trypanosoma, Noctiluca). It seems that the word Heterokaryote would strictly apply to these forms also, although the “heterosis” is not the same as that seen in Ciliata. It would be premature to attempt to introduce a terminology indicating these different specialisations of nuclear structure in the Protozoa until much further study has been given to the subject. It is not at all improbable that researches which are now in progress will in the course of a few years give us, first of all, a better understanding of the chemical nature and activities of the substances which are merely brought into view by colour-staining as form-elements in the nucleus,’ and secondly, a far more critical knowledge than we at present possess of the rudimentarily aggregated and diffuse stainable matter which is interpreted as “nucleus” in some of the Protozoa, in some of the Cyanophyceae, in Schizomycetes, and in the yeasts and hyphae of lower fungi. Whilst therefore recognising the important separation of the Ciliata and Acinetaria effected by having regard to the nuclear structure of those groups and that of the other classes of Protozoa, so far as we at present know them, I am unwilling to emphasise the arrangement of the Protozoa into grades according to their nuclear structure in the present state of knowledge. I should not wish to go farther at present in grouping the classes of Protozoa than to suggest that they should be considered as diverging lines of descent radiating from a central group which possessed the combination of characters presented at the present day by the simpler Flagellata. 1 The researches of Professor Macallum of Montreal in this direction will, it may be hoped, be continued and developed. CHAPTER I.—PROTOZOA SECTION A.—THE PROTEOMYXA ! In the study of the Protozoa a number of forms are found which are difficult to place in any of the larger orders or families. The difficulty arises in many cases from what is called their simplicity of structure, and partly from our ignorance of their entire life-history. The more we learn of the structure of the Protozoa, the more hazardous does it become to apply the expression “‘ simple ” to any living organism, but what is really meant by the term “simple” as applied to these organisms is that they exhibit no definite structure or structures such as skeleton, flagella, or nuclei that are so constant in their form and character that they can be _ seized upon by the systematist and used for purposes of classifica- tion. When characters of this description appear during one phase only of the life-history of an organism they may indicate its affinities if not its true systematic position, but when the life-history is not completely known there may be no characters which can possibly serve for placing the organism with others in any system of classification. In the early history of Protozoology there was a time when it was considered that some of the very small and obscure organisms consisted of a cytode of protoplasm in which there was no structure corresponding with the nucleus of the higher organisms and cells. Such organisms were placed in a class Monera by Haeckel in 1868. Subsequent researches proved that in many of these organisms one or many minute structures occur which give the same reactions as the chromatin of the nucleus, and the conclusion was, in some cases too hastily, drawn that all of them would in time be shown to be nucleated. Modern researches on the nuclear structures of Protozoa have thrown much light on this vexed question. They have shown that the nucleus may discharge into the cytoplasm, or give rise by total fragmentation to, a number of minute granules of chromatin—the chromidia—and that these granules do not degenerate, but retaining their vitality may again aggregate together in the formation of new nuclei. There may thus occur in the life-history of the higher Protozoa a stage which is strictly speaking non-nucleate (akaryote). 1 By Prof. S. J. Hickson, F.R.S. 1 I 2 THE PROTEOMYXA This does not imply, however, that the organism is at this stage devoid of nucleoplasm, but that the nucleoplasm is not concentrated in the form of a definite nucleus or kernel but is scattered or diffused. This conception may be expressed by saying that the stage is akaryote but is not moneran. ‘There is no nucleus but there is nucleoplasm. In Amoeba, Pelomyzxa, and others in which such a stage occurs the nucleus is present during the greater © part of the life-cycle, the akaryote stage being antecedent only te nuclear multiplication or gametogenesis. In'the Proteomyxa, on the other hand, the akaryote condition is, as a rule, of much longer duration, and it is possible that in some cases the diffused nucleoplasm or scattered chromidia do not collect together in any stage to form a defined nucleus. It seems probable, then, that the protoplasm of the Proteomyxa really represents the protoplasm of the higher Protozoa and Metazoa plus the substance of the nuclei. It is a substance which van Beneden (9) in 1871 proposed to call “the plasson,” that is, the formative substance “which is capable of becoming, either in ontogenetic course or in phylogenetic course, monocellular elements after that the chemical elements of the plasson have been separated to constitute a nucleus and a protoplasmic body.” Our knowledge of the nucleus or chromidia of the genera that are here grouped together in the class Proteomyxa is at present very scanty. Vampyrellidium is said to have a nucleus in all stages of its life-history. Zopf states that a definite clear nucleus is present in all species of Vampyrella, but it is often obscured by chlorophyll and other bodies in the cytoplasm. There seems to be little doubt, however, that the nucleus is not present in all stages of the vegetative life of Vampyrella, as several observers who have carefully re-examined its structure have failed to find any definite nucleus. Recently, however, Dangeard (13) has shown that nuclei are present in the cysts, and that they divide by karyo- kinesis. In 7etramyza there are said to be minute nuclei, but these are probably chromidia. In Plasmodiophora true nuclei are un- doubtedly present at the time of spore-formation, as they have been observed to divide by karyokinesis. It is probable also that a defined nucleus is present during the flagellate and amoebula phases of most of the Proteomyxa (Fig. 8, B, H), but it is clear that for a time during the plasmodium stage the nuclei are disintegrated. In Endyonema nuclei appear to be wanting during the active vege- tative phase in the filaments of its host-plant (Lingbya), but definite nuclei are constituted when the body contracts in the formation of the zoocyst. Many of the genera included in the group have been seen only once, and we are still in ignorance of their nuclear condition, but in Gymnophrys, Biomyxa, Gloidium, Leptophrys, and Protamoeba, THE PROTEOMYXA 3 which have been studied by other observers than their original discoverers, no defined nuclei have been found. A considerable number of genera are parasitic upon freshwater algae during at least one stage of their life-history, such as Vam- pyrellidium, Vampyrella, Leptophrys, Endyonema, Enteromyxa, Col- podella, Pseudospora, Gymnococeus,, Aphelidium, Tetramyxa, and Ectobiella. Tetramyxa causes the formation of gall-like growths on Ltuppia and other freshwater plants. Sursulla occurs in horse- dung. Haplococcus occurs in the muscles of the pig, but is appar- ently harmless. ‘The only species that is of any economical import- ance is Plasmodiophora brassicae, Woronin, which attacks turnips Fic. 1 and causes the disease known as _ Letobiella plateawi. A, a specimen attack- “Fingersand Toes,” or “Hanburies.” is Beau er betas of HIE aoe 4 A considerable mumber of genera {he raeuole formal by the host containing are not parasitic and feed upon of the pseudopodium. B, the biflagellate : : zoospore of Ectobiella. (After de Bruyne.) minute animal and _ vegetable organisms. Such genera are C'ymnophrys, Biomyzxa, Protomyza, Gloidiwm, and others. . In the vegetative condition the body emits pseudopodia. These pseudopodia may be roughly arranged in three categories. In Protamoeba, Gloidium, Enteromyxa, etc., the pseudopodia are usually lobate like those characteristic of the genus Amoeba. In Vampyrella, Colpodella, Monobia, Myxastrum the pseudopodia are radiate in position, very delicate and rarely anastomosing, like those of an Actinophrys. In Biomyxa, Gynnophrys, Penardia they are delicate and anasto- mosing, like the pseudopodia of the Foraminifera. In Endyonema, Haplococcus, Aphelidium, and other endoparasites the form of the body is adapted to the spaces of the host and true pseudopodia are not formed. In Protomyza, Myzastrum, Protomonas, Bursulla, Plasmodiophora a number of amoebulae unite to form a plasmodium, and it is possible that plastogamy also occurs in Vampyrella, Leptophrys, and some others. In Monobia a number of stellate individuals unite to form an open network (Fig. 4). A contractile vacuole does not usually occur in Proteomyxa, but it appears to be a constant feature in Gloidiwm and Ciliophrys. Non-contractile vacuoles occur in many of the genera. Although very little is known about the life-history of the Proteomyxa, it seems probable that they all, at some time, form cysts or spores. In Plasmodiophora the protoplasm of the plasmodium breaks up into a large number of simple spores, which are able to 4 THE PROTEOMYXA resist desiccation, and are probably simple hypnocysts.? In other cases the cysts are larger, and the contents give rise to three or four (Vampyrella lateritia, Fig. 2) or a large number (Protomyza, Fia. 2. Cystic phase of Vampyrella. The contents of the cyst have divided into four equal parts, of which three are visible. Fig. 6, and Diplophysalis) of spores, which may be either naked or protected by a membrane. These cysts are protected by one or more cyst-membranes, and the outer of these may be irregular or spiny or gelatinous in texture. Occasionally three or four small areas on the cyst-wall are provided with a thinner membranous coat, and the spores escape by breaking through these areas only (Haplococcus) ; but usually the cyst-wall breaks down and liberates the spores, or the spore escapes through any part of the membranes. In spore-formation the protoplasm usually discharges all extraneous matters, and one (After Lankester o f these peasy a mere large or a number of smaller granules o ejecta are found between the wall of the cyst and that of the spores. There is no evidence at present that any process of conjugation occurs between the liberated zoospores, except in Culiophrys (Cienkowski), and, in the absence of any systematic study of the nuclear substance of the spores, we are not in a position to state that the condition of the nuclei or nucleo- plasm of the spores is in any way different to that of the other phases of life. There is therefore no justification whatever for the assumption that any form of cyst-formation indicates or is associated with a sexual process.! A remarkable phenomenon has recently been described by de Bruyne in Leptophrys villosa. After a period of feeding, the animal becomes spherical in shape and enters upon a period of rest. From the surface there are protrudeda number of deli- cate filaments (Fig. 3) which terminate in hyaline globules. These globules are discharged and the filaments after some time are slowly withdrawn. When conditions are favourable there emerge Fi, 3. from the cyst one or more Leptophrys villosa. A, a specimen actively feed- ing, showing, v, a large non-contractile vacuole ; amoebulae (Monadineae azoo- sporeae, Zopf), or one or more flagellulae (Monadineae zoosporeae, Zopf), The ' According to von Prowazek the nuclei of the spores of Plasmodiophora are formed by karyogamy (Arb. aus den kaiserl. Gesundheitsamte, xxii., 1905, p, 396). d, the diatoms on which it is feeding; and ¢, a tuft of pointed pseudopodia at the posterior end of the body. B,a resting stage of the same animal, pro- vided with filamentous processes, p, which discharge minute globules, s.p, of hyaline protoplasm. (After de Bruyne.) THE PROTEOMYXA 5 amoebulae either grow and become Actinophrys-like in form (V’am- pyrella) or unite to form plasmodia (Leptophrys, Endyonema, ete.). The flagellulae are provided usually with one, but sometimes two (Diplophysalis, Gymnococcus) whip-like cilia, and sometimes also with a vacuole. They sometimes swim about actively and attack the organisms on which they feed (Colpodella, Fig. 8, A); but usually they soon withdraw their cilia and become amoeboid in shape, and the amoebulae thus formed either unite to form plasmodia or grow independently into the adult form. The classification of Proteomyxa has always presented innumer- able difficulties, and even at the present day our knowledge is so incomplete that nothing better than a tentative arrangement of the genera can be suggested. A large number of the genera were placed in a division (Monadineae) of the Mycetozoa (Pilzthiere) by Zopf, others are regarded as Foraminifera nuda by Rhumbler, and Biitschli included several of the genera in the Heliozoa. Zopf further divided his genera into two groups, the Mona- dineae azoosporeae and the Monadineae. zoosporeae. In the former the cysts give rise to amoebulae, and in the latter to flagellulae. It does not appear satisfactory, however, to use the characters of the swarm-spores alone ‘as a basis of classification. Pseudospora, with a flagellate zoospore, is clearly related to Vampyrella and its allies, which have an amoebulate zoospore; and Lnteromyza, Myzxastrum, and other genera, with an amoebulate zoospore, appear to have no close relation to Vampyrella. Fia. 4. Monobia confluens. A number of individuals connected together by protoplasmic strands to form a loose meshwork colony. (After Schneider.) In attempting to classify the Proteomyxa, certain genera stand out as clearly related to other groups of Protozoa. Thus Monobia is closely related to the Heliozoa, Protogenes to the Foraminifera, Protamoeba and Gloidium to the Gymnamoebida, and Plasmodiophora 6 THE PROTEOMYXA to the Mycetozoa. Taking into consideration the form assumed by the pseudopodia, the habit of plasmodium-formation, as well as the character of the zoospores, most of the other genera can be arranged around these as central types. But there still remain some forms whose affinities are at present quite obscure, and these must be separated for the present into a group by themselves. The genera are here arranged in five groups according to their supposed affinities with the other orders of Protozoa. Grovur A. The following two genera appear to have affinities with the Gymna- moebida. Nothing whatever is known concerning their life-history, and it is probable they will prove to be but a stage in the life-history of an Amoeba. Protamoeba, Haeckel, is like an Amoeba, but without any definite nucleus or contractile vacuole. Freshwater and marine. 110 p (Penard). Gloidiwm, Sorokin (Fig. 5), differs from Protamoeba in possessing a contractile vacuole. Occasionally the surface is denticulated. Fresh- water, 71. G. inquinatum, Penard, 385 p. The genus Gringa, Frenzel, “is probably a species of Gloidiwm. Four stages in the division of Gloidiwm quudrifidum. c.v, contractile vacuoles. (After Sorokin.) Group B. The genus Monobia in this group is closely related to Heliozoa. Monopodium and Vampyrella are closely related to one another, and agree with Vampyrellidiwum and Pseudospora in having a stage with delicate radiating pseudopodia like an Actinophrys. Leptophrys has affinities with Vampyrella, but differs from it in the shape of the body, which is irregular. Myzastrwm is in some respects intermediate between the genera included in this group and those in Group D. (LV.)'! Monobia, Schneider (Fig. 4). A number of Actinophrys-like individuals, but without nucleus or contractile vacuoles, and of a bluish ' As the genera included in the Proteomyxa in this volume have been shifted about from one class to another by different authors, the roman figures in brackets have been introduced to indicate to the reader the position assigned to each genus by the leading writers on Protozoology, when it differs from that given to the same genus in the text. Thus the genera marked (I.) were referred to the Monadineae azoosporeae, (II.) to the Monadineae zoosporeae of the Mycetozoa by Zopf; (I11.) to the Foraminifera nuda by Rhumbler (22); (LV.) to the Heliozoa by Biitschli and Schaudinn, THE PROTEOMYXA 3 colour by transmitted light, are united into a colony by the fusion of the ends of their contiguous pseudopodia. Reproduction by fission has been observed, but no process of spore-formation is known, Freshwater. (I.), (LV.) Vampyrella, Cienkowski (Fig. 6, 5). Several species of this widely distributed genus are known. ‘There is an Actinophrys stage in which, according to some authors, there is a nucleus. Vampyrella lateritia attacks Spirogyra by pushing a lobate pseudopodium into the cell and gradually absorbing its contents, V. gomphonematis attacks the stalked diatom Gomphonema, completely surrounding the frustules and absorbing their contents. Cysts are formed surrounded by a single smooth membrane, the animal discharges particles of undigested food Fia. 6. - 1, Protomyxa awrantiaca, Haeckel, plasmodium phase. The naked protoplasm shows branched, reticulate processes and numerous non-contractile filaments It is in the act of engulfing a Ceratium. Shells of engulfed Ciliata (Tintinnabula) are embedded deeply in -the endoplasm, a. 2, cystic phase of Protomyxa; a, transparent cyst-wall; b, protoplasm broken up into spores. 3, flagellula phase of Protomyxa. 4, amoebula phase of the same, the form assumed after a short period by the flagellulae. 5, Vampyrella lateritia, Cienk. Actinophrys stage penetrating a cell of Spirogyra, b, by a process of its protoplasm, c, and taking up the substance of the Spiro- gyra cell, some of which is seen within the Vampyrella, a. 6, large individuals of Vampyrella showing pseudopodia, e, and food-particles, a. (From Lankester, after Haeckel and Cienkowski.) materials and these are found with the shrunken protoplasm within the eyst-wall. Occasionally a second membrane is formed around the shrunken protoplasm. The protoplasm divides within the cyst-wall, and the nuclei of the spores thus formed are 2 mw in diameter and divide by karyokinesis, From the cyst there escape one, but usually four or five amoebulae, which soon develop radiate pseudopodia and float away in search of their food. In some species (e.g. V. gomphonematis) it 8 THE PROTEOMYXA seems certain that several individuals may fuse to form a plasmodium. No contractile vacuoles occur at any stage. The size varies consider- ably, 20-70 pp. They are nearly all freshwater forms, but one species, V. gomphonematis, is also marine. Monadopsis, Klein, is probably a species of Vampyrella. (I.) Vampyrellidium, Zopf. This genus is parasitic on freshwater Algae, particularly on Lingbya. Two kinds of cysts are formed, the zoocysts with a clear homogeneous membrane, and the hypnocysts with a thicker membrane. In other respects it is closely related to Vampyrelia. A nucleus surrounded by a hyaline area is said (Zopf) to occur at every stage. (L.) Leptophrys, Hertwig and Lesser (Fig. 3), appears to be closely related to Vampyrella, but it forms larger vacuolated plasmodia by the fusion of the amoeboid zoospores. It is also characterised by the presence in the protoplasm of numerous paramylum granules. Like Vampyrella it is found parasitic on various freshwater lower Algae. It is either colourless or tinged with chlorophyll. The cysts are sometimes 0°25 mm. in diameter. They give rise to three or four amoeboid zoospores. No nuclei have been observed at any stage. (IV.) Monopodium (Haeckelina), Mereschkowsky, is an Actinophrys-like form with hyaline protoplasm and very delicate radiating pseudopodia attached to foreign bodies by a stalk. 0O°2 mm. White Sea. Archerina (see p. 33). (IV.) Nuclearia, Cienkowski (Fig. 8, E), also appears to be related to Vampyrella, but as a nucleus or nuclei and contractile vacuoles have been observed by several authors, it is perhaps more natural to regard it asa member of the order Heliozoa. (I1.) Pseudospora,! Cienkowski, is a small Proteomyxan, 3-4 , which feeds upon Oedogoniwm, Spirogyra, ete. It is related to Gymnococcus and other members of Group C in producing flagellate zoospores. These zoospores, provided with one or two flagella and a minute nucleus, penetrate the bells of the host-plant and give rise to an Actinophrys-like stage, but they do not fuse to form a plasmodium. When they are fully fed the numerous pseudopodia are withdrawn and an amoeboid form is assumed previous to encystment (Fig. 8, B, C). Dzuplophysalis, Zopf, seems to be closely related to Pseudospora. ~ (1.), (LV) Myzxastrum, Haeckel, was found on the shores of the Canary Islands and is marine. It has a stage with numerous radiating pseudopodia, but forms plasmodia which attain to 0°6 mm. in diameter. The plasmodium encysts as a whole and the protoplasm forms 100 or more spores which give rise to amoeboid zoospores. (IV.) Ciliophrys, Cienkowski (Fig. 8, G, H), probably belongs to this group. It is similar to Nuclearia in some respects, but at times it with- draws its radiating pseudopodia, becomes oval in shape, and swims rapidly by means of a long flagellum. Freshwater. Grovur C. In this group there is a stage when fine branching and anasto- ' For Pseudospora volvocis, see Mastigophora, p. 168. THE PROTEOMYXA 9 TEESE EEE SERRE mosing pseudopodia are formed and the affinities seem to be with the Foraminifera. Arachnula has some affinities with Nuclearta and is re- garded as a Heliozoon by some authors. (I1I.) Protogenes, Haeckel (Fig. 7), is a small spherical organism with very numerous and delicate radiating and anastomosing pseudopodia Neither vacuoles nor nuclei have been observed. Marine. (III.) Biomyxa, Leidy, is a widespread genus occurring both in fresh and salt water. It yf - passes though a spherical stage : / with radiating pseudopodia, but afterwards assumes a variety of elongated or outstretched shapes with a few long, isolated, branch- ing and anastomosing pseudo- podia. One large or many small nuclei are said to occur (Rhum- bler). In J. vagans there are numerous minute contractile (?) vacuoles, but in B. (Gymnophrys) cometa there are none. It occurs in swampy sphagnum ground in tA this country. No definite nuclei | have been observed and nothing : . . : Fia. 7. is known concerning its life- Protogenes primordialis, Haeckel, from Schultze’s history. The genera Gymnophrys, figure. Cienkowski (Fig. 8, D), and Penardia, Cash, seem to be allied to Biomyxa. It has been suggested by Archer that Gymnophrys is but a detached portion of a Gromza, and West (27) has found it in a collection containing a large number of specimens of this Foraminifer. (IIL) Arachnula, Cienkowski (Fig. 8, F), also is closely related to Biomyxa, but it forms long strands terminating in branching extremities provided with tufts of delicate anastomosing pseudopodia, Cysts have been described. It is found in fresh and brackish water. (III.) Pontomyxza, Topsent, is a form closely allied to Biomyxa and Penardia. The body assumes a variety of ribboned or dendritic forms, with numerous or interrupted groups of anastomosing pseudopodia. P. pallida from the Mediterranean Sea is colourless, but P. flava, like Penardia, is golden yellow in colour. P. flava was found in 35-50 metres off the French coast and also in the Mediterranean Sea. The nuclei are said to be very small and reproduction occurs by multiple fission. (IIL) Rhizoplasma, Verworn (26). Spherical or sausage-shaped bodies of an orange-red colour, with numerous anastomosing pseudopodia, 5-10 mm. in diameter when expanded, found in the Red Sea, are placed in this genus. There are 1-3 large transparent vesicular nuclei. The coloured granules circulate in the pseudopodia. fo) THE PROTEOMYXA (IIL.) Dictyomyxa, Monticelli, is like the preceding genus, but with colourless pseudopodia. On Chaetomorpha crassa at Naples. Boderia, Wright (Fig. 9), is marine, orange or brown in colour, with a membranous investment (?), from openings in which protrude three to four long branching pseudopodia. The nucleus or nuclei after a time Fia. 8. A, Colpodella pugnax. Three individuals attacking a Chlamydomonad. B, flagellate zoospore of Pseudospora parasitica ; n, nucleus; v, vacuoles, said to be contractile. C, the amoeboid phase of Pseudospora which succeeds the Actinophrys stage ; s is probably amass of ingested starch-grains. D, Gymnophrys cometu. E, Nuclearia delicatula with three nuclei, n. F, Arachnula impatiens. G, Actinophrys stage of Ciliophrys; n, nucleus. H, flagellate stage of Ciliophrys infusionum ; e.v, contractile vacuole ; n, nucleus. (All after Cienkowski.) disappear, and the protoplasm spreads out in ragged masses on the slides. A number of naviculoid bodies are formed, from each of which a smalk amoebula emerges in a few days. Marine. 1-4 mm. Groue D. Most of the genera included in this group form plasmodia, and their affinities seem to be with the Mycetozoa. No plasmodium-formation has been found in Aphelidium, Colpodella, Pseudosporidium, and Pseudamphi- THE PROTEOMYXA II monas. Zoospores with one or two flagella have been seen in all the genera except Myxodictywm, Bursulla, and Tetramyza, It is possible that Colpodella is related to the Mastigophora. (III.) Protomyxa (Fig. 6, 1) was found by Haeckel attached to the shells of Spirula on the coast of the Canary Islands, in the form of orange-yellow flakes consisting of branching and reticular protoplasm nourishing itself by the ingestion of Diatoms and Peridiniae. This is a plasmodium formed by the union of several amoebulae. The plasmodium en- cysts and gives rise to numerous flagellulae or swarm-spores, The diameter of the cyst is *12--2 mm. The flagellulae pass into an amoe- bula phase, and the amoebulae unite to form the plasmodium. Myzxodictyum, Haeckel, consists of a number of protomyxa-like individuals united by their pseudo- podia to form colonies. It is pelagic in habit and was found by Haeckel at Algeciras in Spain. Marine. (IL.) Gymnococcus, Zopf, occurs in Cladophora, Diatoms, and Cylindro- spermum. It forms a plasmodium. When fully fed it gives rise to zoo- cysts, from which three to twelve Via. 9. biflagellate zoospores escape. Boderia turneri. N, nucleus. (After Wright.) (II.) Aphelidium, Zopf, lives in the cells of Coleochaeta and in macerations of plant tissues. Hypnocysts furnished with an operculum are formed. A nucleated zoospore with one flagellum has been found in A. lacerans (de Bruyne). (II.) Protomonas, Cienkowski, has biflagellate zoospores which become amoeboid and unite to form a plasmodium. Freshwater and marine. (II.) Colpodella, Cienkowski (Fig. 8, A), is possibly allied to Protomonas. The zoospores have only one flagellum, and attack MMJastigophora before they become amoeboid. They do not, however, form plasmodia. CII.) Tetramyxa, Gobel, forms large galls on various water- plants, especially Ruppia. (II.) Plasmodiophora, Woronin, is the cause of the disease of turnips known as ‘Fingers and Toes,” or “ Hanburies” (German, Herniekrank- heit). The spores are found in damp ground. Each spore gives rise to a minute nucleated amoeboid zoospore with a single flagellum. This penetrates into the cells of the root and loses its flagellum. It increases in size and the nuclei divide. After a time plasmodium-formation begins by the fusion of neighbouring amoebulae, and the tissues of the host-plant disintegrate. As soon as the plasmodium is formed the nuclei increase rapidly by karyokinesis, but according to Nawaschin (21) there is a period 12 THE PROTEOMYXA when the plasmodia exhibit no trace of nuclei, the nuclear substance being apparently distributed throughout the whole plasmodium. Subsequently the plasmodium breaks up into a great number of minute spherical spores, Pseudamphimonas, de Bruyne, was found on Caulerpa at Naples. The zoospores are biflagellate and extremely amoeboid. They withdraw their flagellae, and two or three have been seen to fuse together to form a plasmodium. (I.) Bursulla, Sorokin, is found in horse-dung. A number of amoebulae with long pointed pseudopodia unite to form a plasmodium. The plasmodia contract and form either stalked cysts (51 4), the contents of which divide and emerge as eight amoebulae, or they give rise to naked spherical cysts with rosy contents and an outer cortex, from each of which a single stalked zoospore emerges. Group E. The affinities of the genera included in this group are quite obscure. (I.) Enteromyxa, Cienkowski, forms, by the fusion of amoeboid zoospores, long vermiform plasmodia (0°5-1 mm.) with short tubercular pseudopodia, These break up into segments, which encyst and give rise to two or seldom more amoeboid zoospores. It feeds on Oscillatoria. (I.) Endyonema, Zopf, forms cylindrical cysts of considerable length in the threads of filamentous algae. Nuclei are said to occur previous to cyst-formation. Ectoliella, de Bruyne (Fig. 1), was found in the form of a biflagel- late pyriform zoospore. It attacks Licmophora and other diatoms, with- draws the flagella and pushes a pseudopodium into the protoplasm of its prey. When the contents of the diatom are assimilated, the amoeboid organisms wander away and encyst. Haplococcus, Zopf, is found in the muscles of the pig. Two kinds of cysts are described by Zopf, the zoocysts (16-22 4) and the hypnocysts (25-30 4). The membrane surrounding the former is thinner in some places than elsewhere, and from them escape six to fifteen amoeboid spores, ‘The further history of the hypnocysts has not been followed. Pseudosporidium, Zopf, was found by Brass in vegetable infusions, It is amoeboid in form, with short blunt pseudopodia, a nucleus, and a vacuole. The cysts give rise to numerous small flagellate zoospores. Schizogenes, Pouchet, was found in the haemocoel of freshwater Ostra- cods and Copepods, It consists of small plastids of hyaline protoplasm, ‘01-03 mm. without vacuoles or nucleus, of indefinite form, and devoid of pseudopodia, It divides into parts, which become new individuals, Bathybius, Huxley, and Protobathybius, Bessels, are no longer regarded as living organisms. It seems probable that both forms represent a colloid precipitate of calcium sulphate thrown down by the action of aleohol on sea-water (Murray). —— OO eV . 1 See Note, p. 4. LITERATURE OF THE PROTEOMYXA 13 LITERATURE. The following recent general works on Protozoology will be found useful to students :— 1. Braun. Animal Parasites of Man. Translated by F. V. Theobald. 1906. Biitschli, O. Protozoa. Bronu’s Klassen und Ordnungen des Thierreichs, Calkins, G. N. Protozoa. Columbia University Biol. Series. 1901. . Cash, J. The British Freshwater Rhizopoda and Heliozoa, vol. i. Ray Society, 1905. 5. Dojlein, F. Die Protozoen als Parasiten und Krankheitserreger. Jena, 1901. 6. Hartog, M. M. Protozoa. Cambridge Natural History, vol. i., 1906. 7. Lang, A. Lehrbuch der vergleichende Anatomie. Protozoa. 1901. 8. Penard, £. Faune rhizopodique du bassin du Léman. 1902. gl. The following refer particularly to Proteomyxa :— 9. Beneden, E. van, Q. J. Micr. Sci. xi., 1871, p. 254. 10. Brass. Biol. Studien, i., 1883-4, p. 70. (Pseudosporidiwm.) ll. de Bruyne, C. Arch. Biol. x., 1890. (Zctobiella, etc.) 12. Cienkowski. Arch. mikr. Anat., 1865, 1876. 13. Dangeard, P. A. Le Botaniste, (2), 1890, p. 33, and (7), 1900, p. 131. 14. Gébel. Flora, No. 28, 1884. (Tetramyzxa.) 15. Haeckel, E. Monogr. der Moneren. Jen. Zeits. iv., 1868. System. Phylog. der Protist. u. Pflanzen. Berlin, 1894. 17. Hoogenraad, H. K. Arch. Protist. viii., 1907. (Vampyrella.) 18. Mereschkowsky. Arch. mikr. Anat. xvi., 1879. (Monopodium.) 19. Monticelli. Boll. Soc. Napoli, xi., 1897. (Dictyomyzxa.) 20. Murray, J. P. R. Soc. London, xxiv., 1876. 21. Nawaschin. Flora, 1899, p. 404. (Plasmodiophora.) - 22. Rhumbler, LZ. Arch. Protist. iii., 1904. 23. Schneider, A. Arch. mikr. Anat. vii., 1878. (Monobdia.) 24. Sorokin. Ann. Sci. Nat. Bot. (6) iii., 1876; Morph. Jahrb. iv., 1878. (Gloidium. ) 25. Topsent, E. Arch. Zool. Expér. (3) i., 1893. (Pontomyzxa.) 26. Verworn. Arch. ges. Physiol. lxii., 1896. (Rhizoplusma.) 27. West, G. S. J. Linn. Soc. Zool., 1901, xxviii. p. 308. l.c., 19038, xxix. p. 108. 29. Woronin. Pringsheim’s Jahrbiicher, xi. (Plasmodiophora.) 30. Wright, S. Journ. Anat. Physiol. i., 1867. (Boderia.) 31. Zopf, WV. Handbuch der Botanik. Edited by A. Schenk. Bad. iii., pt. 2, 1887. THE PROTOZOA (continued) SECTION B.—THE HELIOZOA ! THE term Heliozoa is commonly used to include a number of Protozoa, generally inhabitants of fresh water, with few characters in common except the possession of straight, radial pseudopodia which rarely anastomose, and the absence of anything like a capsular membrane dividing a central portion of the body from a peripheral portion, such as is found among the Radiolaria. The more highly specialised members of the group have a spheroidal body, which rarely exhibits amoeboid change of shape, divided into a more vacuolated Fia. 1. Actinosphaerium Eichhorni, Ehrb. Fia. 19. a and b, Copromyxa protea, Fayod. a, a simple, b, a branched form of sorus, slightly magnified (after Fayod.). e¢ and d, Poly- sphondylium violacewm, Brefeld. c, a young sorus, seen in optical section, with a mass of amoebae grouped round the stalk, and others still extended about the base, x 110. d, a sorus approaching maturity. The stalk has become compound. The lowest whorl of secondary sori is complete, those above it are in varying degrees of completeness, x 20. (After Brefeld. From Zopf, 24.) organisation of the Metazoa. Some of the amoebulae secrete a firm membrane and become joined end to end to form a stalk (Fig. 19, cand d), attached below to the substratum, and up this the other amoebulae climb and pass into the encysted condition at the top as a naked cluster of spores. In Dictyostelium the stalk is long and simple ; in Polysphondylium it is branched (Fig. 19, d). The supporting structures of the Sorophora are evidently of a different nature from those of the Euplasmodida, in which they are - not cellular, but formed as secre- tions of the protoplasm. It is, of course, possible that the pseudoplasmodia of the Soro- phora may represent a stage in the evolution of the true plas- modium, which in the other group is such an important phase of the life-cycle; but it appears more — probable that both Euplasmodida and the Sorophora are to be derived from some simple forms with a life-history resembling that of Protomonas or Bursulla among the Proteomyxa. Two hundred and sixty-five species of the Euplasmodida are described in the British Museum Catalogue (18); Zopf (24) enumerated nine species of Sorophora, and Olive (20), more recently, twenty. THE MYCETOZOA 61 The classificatory characters are mainly derived from the sporangia, the capillitium (when it is present), and the spores. Some species stand apart from their allies with great distinctness. but in many genera examples intermediate in character between the species are of common occurrence, and it is only by large experience of the frequency with which the forms, as they occur in nature, group themselves about certain centres that a correct idea of the species can be attained. The distribution of most species appears to be, so far as it has yet been determined, world-wide in the more humid parts of the temperate and tropical regions of the globe, where woodlands and forests offer conditions favourable to their existence—a fact which is doubtless dependent on the ease with which the minute spores are carried in currents of air. No Mycetozoa have hitherto been met with in a fossil state, though from the degree of differentiation of the sporangia we cannot doubt that the group is of high antiquity, and has in past time, as at the present, played an important part in the disintegration of vegetable tissues. It is remarkable that no parasitic organisms are known to live on Mycetozoa, a fact which Stahl attributes to the readiness with which foreign bodies are cast out by the organisms in the plas- modial stage. In writing this account of the Mycetozoa constant reference has been made to de Bary’s classical work (1-3), to the papers of Cienkowski (5-8), and to Zopf’s treatise (24). But I wish especially to acknowledge my obligations to the work of my father, Mr. A. Lister, on their life-history and classification. So far as I have been able to speak of the biological aspects of the group from my own knowledge, it is mainly to the opportunities I have had in following this work that I am indebted. The proof-sheets of this article have been submitted to my father, and I feel that its authority is greatly enhanced when I add, as he allows me to do, that the conclusions are in the main in accordance with his views. SuB-CLASS I. EUPLASMODIDA. The contents of the spores develop, on hatching, into flagellate zoospores. Amoebulae completely fused to form the plasmodium, which is the dominant phase of the vegetative period. Division I. ENDOSPOREAE. Spores developed within sporangia. Conort I. AMAUROSPORALES. Spores violet, or violet-brown. 62 THE MYCETOZOA Susp-CoHort A. CALCARINEAE. Sporangia provided with lime. ORDER 1. Physaraceae. Lime in minute, round granules. A. Capillitium a coarse network charged with lime throughout. Genus—Badhamia, Berk. (Figs. 9 and 10). B. Capillitium a delicate network of threads with vesicular expansions filled with lime-granules (=lime-knots). a. Sporangia com-. bined into a convolute aethalium. Genus—Fuligo, Haller (Fig. 16). f£. Sporangia single, scattered, or aggregated. a, sporangium wall membranous. Genera—Physarum, Pers. (Fig. 13, a). Sporangia sub- globose or in the form of plasmodiocarps. Physarella: Peck. Sporangia tubular. 6, sporangium wall cartilaginous throughout, or at the base only. Genera—Cienkowskia, Rost. Sporangia in the form of plasmodio-- carps ; capillitium with free hooked branches. Crateriwm, Trent (Fig. 13, d). Sporangia goblet-shaped or subglobose. Leocarpus, Link. Sporangia ovoid, glossy. C. Capillitium without lime-knots. Genera-—Chondrioderma, Rost. (Fig. 13, e). Sporangium wall of two layers, more or less combined. Trichamphora, Jungh. Sporangium wall of one layer, fragile ; sporangia saucer-shaped. D. Lime confined to the stalk and columella ; spore wall membranous. Genus—Diachaea, Fries. OrpDER 2. Didymiaceae. Lime deposited in the form of crystals or crystalline dises on the outer surface of the sporangium wall ; capillitium without lime-knots. Genera— Didymiuwm, Schrader (Fig. 17). Lime in crystals ; sporangia simple. Spumaria, Pers. (Fig. 13, g). Lime in crystals ; sporangia united into an aethalium. Lepidoderma, de Bary. Lime in crystalline discs (Fig. 13, h); sporangia simple. Susp-Conort B. AMAUROCHAETINEAE. Sporangia without deposits of lime ; capillitium dark brown or violet brown. Orver 1. Stemonitaceae. Sporangia stalked, the stalk extending within the sporangium as a columella ; sporangium wall a single delicate membrane, often evanescent. Genera—Stemonitis, Gleditsch (Fig. 14, a-e). Sporangium wall evanescent ; capillitium springing from all parts of the elongated columella, its ultimate branches forming a superficial net. Comatricha, Preuss. Like Stemonitis, but the branches of the capillitium not forming a superficial net. ner- thenema, Bowman, Sporangium wall evanescent ; columella reaching to the apex of the sporangium, where it forms a superficial expansion from which the capillitium springs. Lamproderma, Rost. Sporangium wall somewhat persistent, columella about half the height of the sporangium. THE, MYCETOZOA 63 Clastoderma, Blytt. Sporangium wall partly evanescent, persisting in the form of minute discs, at the tips of the rigid capillitium threads ; columella short or none. chinostelium, de By. A minute colourless form with long stalks and a sparsely-branched spiny capillitium. OrprerR 2. Amaurochaetaceae. Sporangia combined into an aethalium ; capillitium of irregular strands and threads, or complex. Genera—Amaurochaete, Rost. Capil- litium of irregular branching threads. Drefeldia, Rost. Capillitium of horizontal threads, with many-chambered vesicles. Couort II. LAMPROSPORALES. Spores variously coloured, never violet. Susp-CoHort A. ANEMINEAE. Capillitium absent, or not forming a system of uniform threads except in Alwisia. ORDER 1. Heterodermaceae. Sporangium wall membranous, beset with minute round granules, and (except in Lindbladia) forming a net in the upper part. Genera— LTindbladia, Fries. Sporangia sessile, compacted or aethalioid, the wall not forming a net in the upper part. Cribraria, Pers. Sporangia stalked ; sporangium wall with thickenings in the form of a delicate persistent net, expanded at the nodes. Dzctydiwm, Schrader (Fig. 14, f). Sporangia stalked ; sporangium wall with thickenings in the form of longitudinal ribs connected by delicate threads. OrpDeER 2. Liceaceae. Sporangia solitary, sessile or stalked ; sporangium wall cartilaginous ; capillitium and columella absent. Genera—Licea, Schrader. Sporangia sessile, globose or in the form of plasmodiocarps. Orcadella, Wingate. Sporangia stalked, furnished with a lid of thinner substance. OrpER 3. Tubulinaceae. Sporangium wall membranous, without granular deposits ; sporangia tubular, compacted together. Genera — Tubulina, Pers. Columella absent. Stphoptychiwm, Rost. A hollow pseudo-columella is present, connected by tubular extensions with the sporangium wall. Alwisia, Berkeley and Broome. Sporangia stalked ; with tubular threads attached to the base and apex of the sporangium wall. OrpDER 4. Reticulariaceae. Aethalia, with the sporangium walls incomplete, perforated, and forming a spurious capillitium. Genera — Dictydiaethalium, Rost. Sporangium walls cap-shaped above and continued down to the base in four to six straight threads. Enteridiwm, Ehrenberg. Walls of 64 THE MYCETOZOA convoluted sporangia forming a tissue of interarching bands. Reticularia, Bulliard. Walls of convoluted sporangia forming tubes and folds with numerous anastomosing threads. ORDER 5. Lycogalaceae. Sporangia forming an aethalium ; pseudo-capillitium consisting of branched colourless tubes, the remains of the walls of the fused sporangia. Genus—Lycogala, Micheli. Sus-Conort B. CALONEMINEAE. Capillitium a system of uniform threads. OrveER 1. Trichiaceae. Capillitium threads with spiral or annular thickenings. Free or united into an elastic network, Trichia, Haller (Figs. 11, 12, and 15, a-c), Capillitium abundant, threads free, with spiral thickenings. Oligonema, Rost. Capillitium scanty, threads free, with imperfect spiral thickenings. Hemitrichia, Rost. (Fig. 15, d). Capillitium threads combined into a net- work, with spiral thickenings. Cornuvia, Rost. Sporangia in the form of plasmodiocarps ; : eapillitium threads combined into a network, with annular thickenings. OrpDER 2. Arcyriaceae. Capillitium combined into an elastic network with thickenings in the form of cogs, half-rings, spines, or warts. Genera—Arcyria, Hill (Fig. 15, e-f). Sporangia stalked ; sporangium wall evanescent above, persistent — and membranous in the lower third. Lachnobolus, Fries. Sporangia sessile, clustered ; sporangium wall single, persistent, not thickened with granules. Perichaena, Fries. Sporangia sessile or in the form of plas- modiocarps ; sporangium wall double, at least at the base, the outer layer thickened with angular granules. OrveER 3. Margaritaceae. Sporangia normally sessile; sporangium wall single, smooth, trans- lucent ; capillitium abundant, not consisting of separate threads, nor combined into a net. Genera—Margarita, Lister. Capillitium profuse, long, coiled, and hair-like. Dianema, Rex. Capillitium of nearly straight threads, without spiral thickenings, attached at both ends to the sporangium walls. Prototrichia, Rost. Capillitium of fasciculate threads, attached above or below to the sporangium wall, and spirally thickened. Division II. Exospornranr. Spores developed on the surface of sporophores. Orper 1. Ceratiomyxaceae. Sporophores fragile and evanescent, branched ; spores white, borne singly on filiform stalks arising from the areolated sporophore. Genus— Ceratiomyxa, Schroeter (Fig. 18). THE MYCETOZOA 6s Sup-Ciass II. SorRopHORA. A flagellate stage is absent from the life-history. The amoebulae become aggregated prior to spore-formation, but do not fuse to form a true plasmodium. In the more highly developed genera some of the aggregated amoebulae are modified to form a stalk on which the remainder are borne after encystment in naked clusters (sori). - OrpDER 1. Guttulinaceae. The aggregation of amoebulae, prior to spore-formation, to form the pseudo-plasmodium, is incomplete in Copromyxa. ‘The amoebulae have the limax form, and the shape of the sori is indefinite. Genera—Oopromyxa, Zopf (Fig. 19, a and 6). Sori wart-like or spindle-shaped, 1-3 mm. high, formed on the surface of the nidus, None of the amoebulae are differentiated to form a stalk. On horse and cow dung. Guttulina, Cienk. Some of the aggregated amoebulae are dif- ferentiated to form a short stalk on which the sorus is borne. On decaying wood or horse-dung. ORDER 2. Dictyosteliaceae. A pseudo-plasmodium is formed prior to spore-formation. Some of the aggregated amoebulae are modified to form a stalk. The sori have a definite shape. Amoebulae with short pointed pseudopodia. Genera— Dictyostelium, Brefeld. Stalks unbranched, the spores without definite arrangement in the sori. On dung of herbivorous animals. Acrasis, van Tieghem. Spores arranged in rows, like strings of beads, at the ends of the stalks. On beer-yeast. Polysphondylium, Brefeld (Fig. 19, ¢ and d). Sori globular, on branched stalks, which attain 1 cm. in length. On horse-dung. POSTSCRIPT. Since the foregoing account of the Mycetozoa was written papers have been published, in part of a preliminary character, which appear to throw light on the nuclear history. In the Endosporeae, Fraulein H. Kranzlin! has described a fusion of the nuclei in pairs, prior to the mitosis which precedes spore-formation, in the young sporangia of Arcyria, and this result is corroborated by Jahn.? The number of chromosomes at this division Jahn believes to be sixteen (“8 double chromosomes”) in Arcyria (at least double that which Jahn found in the division of the zoospore in other genera). In Fuligo Harper? found the number to be twelve in the mitosis preceding spore-formation. 1 “Zur Entwicklungsgeschichte der Sporangien bei den Trichien und Arcyrien,”’ Arch. f. Protistenkunde, Bd. ix. (1907), p. 170. 2 “Myxomycetenstudien—6. Kernverschmelzungen und Reduktionsteilungen,” Ber. d. deutsch. botan. Gesellschaft, Bd. xxv. (1907), p. 23. ® “Cell and Nuclear Division in Fuligo varians,” Botanical Gazette, vol. xxx. (1900), p. 217. 5 66 THE MYCETOZOA These authors suggest that the fusion of nuclei in the young sporangium is a long-deferred karyogamy, separated by the whole of the plasmodium | stage, with its many nuclear divisions, from the plastogamy (the fusion of the amoebulae) by which the plasmodium originates. They thus regard the mitosis preceding spore-formation as the one nuclear division in the life-cycle in which the full (‘‘somatic ”) number of chromosomes is present. Jahn (l.c.) and, subsequently, Olive! also state that a fusion of nuclei occurs in Ceratiomyxa prior to the formation of the spores. The fusion is followed by four according to Jahn, by two according to Olive, mitotic divisions, and the ripe spore is four-nucleated (not one-nucleated, as in- dicated above (Fig. 18, c)). It would thus appear that there are, at any rate, two mitotic divisions before spore-formation in Ceratiomyxa and only one in the Endosporeae. The spores are thus not strictly homologous in the Endosporeae and Exosporeae. That of Ceratiomyxa is more advanced than the spore of the Endosporeae in that at least two mitotic divisions subsequent to karyogamy have occurred (and the four nuclei thus arising are contained in the spore), but it is less advanced in that no cleavage of the protoplasm about the products of division has taken place. LITERATURE. . de Bary, A. Die Mycetozoen. Zeits. f. wiss. Zool. vol. x. (1860), p. 88. Die Mycetozoen. 2° Auflage, Leipzig, 1864. Comparative Morphology and Biology of the Fungi, Mycetozoa, and — Bacteria. Translation. Oxford, Clarendon Press, 1887. 4. Bitschli, O. Protozoa, Abth. g, Sarcodina. Bronn’s Thierreich, Bd, i. 5. Cienkowski, L. Die Pseudogonidien. Pringsheim’s Jahrbiicher, i. p. 371. Ne 6. Zur Entwickelungsgeschichte der Myxomyceten. Pringsheim’s Jahr- biicher, iii. p. 325 (published 1862). (f Das Plasmodium. bid. p. 400 (1863). 8. —— Beitrige zur Kenntniss der Monaden. Arch, f. mikr. Anat. i. (1865), p. 208. 9. Famintzin, A., and Woronin, M. Ueber zwei neue Formen von Schleimpilzen, Ceratium hydnoides, A. and Sch., and C. porioides, A. and Sch. Mém. de l’Acad. Imp. d. Sciences de St. Pétersbourg, sér. 7, T. 20, No. 3 (1878). 10. Greenwood, M., and Saunders, EF. Rk. On the Role of Acid in Protozoan Digestion. Journ. of Physiology, xvi. (1894), p. 441. 11. Jahn, E. Myxomycetenstudien—3. Kerntheilung u. Geisselbildung bei den _ Schwirmern von Stemonitis flaccida, Lister. Ber. d. deutschen botanischen Gesellschaft, Jahrg. 1904, Bd. xxii. Heft 2. 12. Krukenberg. Ueber ein peptisches Enzym im Plasmodium der Myxomyceten und im Eidotter vom Huhne. Unters. aus d. physiol. Inst. in Heidel- berg, 1878, ii. p. 278. 1 “Qytological Studies in Ceratiomyxa,” 7'rans. Wisconsin Academy of Science, Arts, and Letters, vol. xv. (1907), pt. 2, p. 753; and “ Evidences of Sexual Repro- duction in Slime Moulds,’’ Science (N.S.), vol. xxv. (1907), p. 266. LITERATURE OF THE MYCETOZOA 67 138. Lankester, L. k. Article ‘‘ Protozoa” in Encyclopaedia Britannica, 1891. 14. Lister, A. Notes on the Plasmodium of Badhamia utricularis and Brefeldia maxima. Ann. of Bot. vol. ii. No. 5 (1888). 15. On the Ingestion of Food Material by the Swarm-Cells of Mycetozoa. Journ, Linn. Soc. (Botany), vol. xxv. (1889), p. 435. 16. On the Cultivation of Mycetozoa from Spores. Journ. of Botany, Jan. 1901. Ly On the Division of Nuclei in the Mycetozoa. Journal of the Linnean Soc. (Botany), xxix. (1893). 18. —— A Monograph of the Mycetozoa. Brit. Museum Catalogue. London, 1894. 19. Metschnikoff, EL. Recherches sur la digestion intracellulaire. Annales de l'Institut Pasteur, 1889, p. 25. 20. Olive, EH. W. Monograph of the Acrasieae. Proc. Boston Soc. of Nat. History, vol. xxx. No. 6 (1902), 20a. Penard, E. Etude sur la Chlamydomyxa imontana. Arch. f. Protisten- kunde, Bd. iv. Heft 2 (1904), p. 296. 21. Plenge, H. Ueb. d. Verbindungen zwischen Geissel u. Kern bei d. Schwarmerzellen d. Mycetozoen . .. Verh. d. nat.-hist. med. Vereins zu Heidelberg, N.F. Bd. vi. Heft 3, 1899. 22. Stahl, E. Zur Biologie der Myxomyceten. Bot. Zeitung, Jahrg. 42 (1884), pp. 145, 161, and 187. 23. Strasburger, H. Zur Entwickelungsgeschichte d. Sporangien y. Trichia fallax. Botanische Zeitung, 1884. 24. Zopf, W. Die Pilzthiereo der Schleimpilze. Schenk’s Handbuch der Botanik, 1887. Zur Kenntniss der Labyrinthuleen, einer Familie der Mycetozoa. Beitrige zur Physiologie u. Morphologie niederer Organismen. Heft 2 (1892), p. 36, Leipzig. 25. THE PROTOZOA (continued) SECTION D.—THE LOBOSA ! GyMNomyxA (Homokaryota), with lobate or pointed unbranched pseudopodia without an axis and with one or more definite nuclei. In a large number of the characteristic genera of Lobosa the body consists of a small plastid of protoplasm protruding a few lobate pseudopodia by means of which a slow progression is — effected, and exhibiting one nucleus and a contractile vacuole. In addition to these characteristic forms, however, other genera must be included in the same class in which the body is protected by membranous or rigid shells (Thecamoebida), with radiating and pointed pseudopodia (T'richosphaerium, etc.), with two (Arcella), or numerous nuclei (Pelomyza), and with no contractile vacuole (Endamoeba, ete.). In many Lobosa, such as Amoeba terricola (Penard [20]) and others, the superficial protoplasm secretes a membranous envelope through which the pseudopodia may be protruded or particles of food ingested. In Tichosphaerium the envelope is relatively thick, gelatinous in texture, and provided with a series of very delicate radiating spicules, mainly composed of carbonate of magnesia. Spicules similar to these are also found in the ecto- plasm of Amoeba pilosa (Cash), in which no true membrane is — formed. In Dinamoeba (Leidy) the spicules occur in a hyaline jelly that surrounds the body. In the Thecamoebida a definite shell is formed through which the pseudopodia cannot penetrate. In this case the pseudopodia can protrude only through a definite and permanent mouth or pore in the shell, which it is convenient to call the pylome (Hartog). In some forms of Amoeba and in other genera there is often seen an apparent differentiation of the protoplasm into a clear outer layer, called the ectoplasm, and a more granular and more fluid central substance called the endoplasm. ‘This appear- ance is more clearly defined when the protoplasm is very active and several pseudopodia are protruded. In the quiescent stages — and conditions of life the ectoplasm usually disappears or becomes extremely attenuated, and in species or forms with only one or two — 1 By Prof. 8. J. Hickson, M.A., F.R.S. 4 68 THE LOBOSA 69 pseudopodia it can be clearly observed only on the pseudopodia themselves (Fig. 12, 2). It seems probable, therefore, that in the Lobosa there is no true differentiation of the cytoplasm, and that the appearance known as ectoplasm is only due to the temporary withdrawal of metaplasmic particles from the superficial parts of the active cytoplasm. At the surface of an Amoeba there may always be seen a dark border which has the appearance of a very thin pellicle. This pellicle may be traced on the sides of the pseudopodia, but fades away towards their extremities, becoming extremely attenuated at the active terminal point. Immediately below this pellicle there is a layer of very hyaline ectoplasm. In carefully prepared sections the hyaline ectoplasm is found to be not strictly homogeneous, but to possess an alveolar structure similar in general characters to that of other forms of protoplasm. At the actual surface there is a single layer of alveoli, in which, as in artificially prepared oil foams, the sides vertical to the surface are parallel, or almost parallel, to each other, giving the appearance of a row of fine vertical striae. It is apparently this marginal alveolar layer which constitutes the pellicle. The movements of an Amoeba may be best interpreted on the basis of the alveolar hypothesis of the structure of protoplasm. The protrusion of a pseudopodium begins with a lowering of the surface tension of the marginal alveolar layer over a small area on the surface. This is followed by a flow of endoplasm towards the area of reduced surface tension. It has been suggested that the initial stages are accompanied by a rupture of some of the alveoli at the surface, which liberates a fluid—the enchylema—and that this causes a local diminution of the surface tension. It is possible that the release of enchylema may continue during the whole of the process of the protrusion of a pseudopodium, and stop when the pseudopodium comes to rest. During the active protrusion of a pseudopodium there may be observed a rapid centrifugal flow of endoplasm towards the peri- phery, called the axial stream. At the apex this stream spreads outwards like a fountain, and is continued as return currents on the surface. Similar fountain-like currents have been observed in the movements of various artificially prepared foams, but in the living protoplasmic pseudopodium the velocity of the return currents diminishes more Feet rapidly and soon comes to rest (Fig. 1). In an__ Diagram to show Amoeba such as A. limaz, in which, as a rule, only ae es ae one pseudopodium is formed, there is a reverse Charente fountain current at the posterior end, the particles at the surface flowing towards the axis and joining in the axial stream flowing in the direction of the advancing pseudopodium. But in 70 THE LOBOSA ‘ this case the actual posterior end is not involved in the current, and by the increase of surface tension becomes folded or wrinkled, giving sometimes an appearance of several small pseudopodia (Fig. 12, 2). In polypodious Amoebae similar reverse currents may be ob- served in retreating pseudopodia, and in areas of the body that are supplying materials for the axial streams of advancing pseudopodia.! Nucleus.—The nucleus of the Lobosa in its resting condition usually exhibits a well-defined membrana limitans. The chromatin is in the form of a number of spherical or irregular particles frequently collected together round the periphery, leaving a more or less clear space in the centre. In some cases a very delicate network of fibrils has been observed, which is regarded as linin (Fig. 2). One or more nucleoli composed of a substance which differs chemically in some of its reactions from chromatin may or may not be present. In Paramoeba eilhardi there occurs a deeply staining body in proximity to the nucleus, which * was termed by Schaudinn (25), who described it, Fic. 2. the “nebenkérper” (Fig. 4, c). This body divides Nucleus of Pelomyza. previous to the division of the nucleus, and the (After Bott.) A “0 a two parts take up a position at opposite poles of the spindle. This body is usually regarded as a “nucleolar cen- trosome.” A body corresponding to this has also been found by Fic. 5. The nucleus of the Fic. 3. Fia> 4. same species _ dividing. Dividing nueleus of ’ — ce Pe. Amoeba limaxr. m.l, the The resting nucleus as divided into two membrana limitans of the (N) and “nebenkérper” parts, which occupy a nucleus: ¢, the nucleo- (c) of Paramoeba eilhardi. position at the foci of the lar centrosome ; ch, the (After Schandinn.) central spindle. ch, the chromosomes arranged somes : ; i chromosomes arranged in an equatorial band. in an equatorial band. ‘ : (After Vahlkampf.) (After Schaudinn. ) Vahlkampf in the division of the nucleus of Amoeba lima (Fig. 3), but in this case the nucleolar centrosome lies within the nuclear membrane. ' The subject of amoeboid movements has of recent years attracted the attention of many observers. ‘The views expressed by Biitschli (/nvestigations on Microscopie Foams, ete., transl. by Minchin, 1894) have been opposed by Jennings (14), but Jennings’ views have been more recently criticised by Rhumbler (23). ® For a discussion on the nature of these bodies, see Goldschmidt and Popoff, Archiv f. Protist, viii., 1907, p. 321. : THE LOBOSA 71 Although the presence of a defined nucleus is regarded as one of the characters of the class, it has been shown that the nuclei sometimes disintegrate and discharge their chromatin into the cytoplasm as scattered granules. This occurs as a result of starvation in Pelomyaa (Bott [2]), and as an antecedent to the formation of sexual or reproductive nuclei in Hndamoeba. Chromidia.—In addition to the chromatin contained within the boundaries of the nuclei, there may be present in the cytoplasm of many Lobosa irregular scattered granules or a fine network of a substance which gives the same reactions and is probably of the same nature as chromatin. In some cases, Difflugia (Fig. 6), the network entirely envelops the nucleus or nuclei, but in others it is separated from the nuclei, Arcella, Cochliopodium, etc. (Figs. 19 and 21), by a halo of clear protoplasm. These granules are called the chromidia, and the network is called the chromidial network (Fig. 6, ch). The chromidia may arise by the migration of particles of chromatin from the nucleus into the cytoplasm or by the disintegra- tion of nuclei, but it seems probable that in some cases they may arise de novo in the cytoplasm. The fate of the chromidia is varied. They may either give rise to the nuclei Fig of gametes or of swarm-spores (Centro- Section tnronan uaa Spt : : showing the nucleus (NV) surrounded pyxis), or they may accumulate in groups by the chromidial network (ch). |p, : Z : pylome; th, theca wall. (After and give rise to new nuclei of the Hertwig.) ordinary type in the cytoplasm (4rcella, Pelomyza), in which cases they are called Idiochromidia. Or, on the other hand, they may be associated with the assimilating or vegetative functions of the cytoplasm and disappear when their activity is exhausted, in which case they are called Trophochromidia. Lefringent and Crystalline Bodies—In many Lobosa crystalline bodies and vesicles containing a strongly refracting substance or fluid occur in great numbers in the cytoplasm. Very often they are far more numerous and conspicuous during the stages and conditions of life when active feeding is in progress than in conditions of starvation or reproduction. They are usually regarded as of the nature of reserve food materials. In Amoeba dofleini, Neresheimer (18) found that the crystalline body, proteid in composition, is associated with a trophochromidium which is probably the active principal of its formation. Veley (34) has shown that the refracting bodies of Pelomyza are proteid in nature. On the other hand, Zuelzer (35) has described the bodies 72 THE LOBOSA formed by the trophochromidia of Dvzflugia as carbohydrate in composition, but the crystalline and other bodies of Trichosphaerium, according to Schaudinn, give differ- ent reactions. Vacuoles. —In nearly all the freshwater and marine Lobosa there is at least one contractile vacuole. In Pelomyxa and some of the Theca- moebida, however, contractile vac- uoles have not been found. The endoparasitic Amoebida have no contractile vacuoles, In addition to the contractile vacuole numerous non-contractile vacuoles containing a fluid of unknown constitution ahegnall portion of she setoplas ¢t but probably nearly pure water caremngent proteld bodies: basymb occur in the endoplasm. chromidia ; v, water vacuoles. (After Bott.) When a particle of food occurs — in a non-contractile vacuole it is” usually called a food-vacuole, and the fiuid in such vacuoles has been shown in some cases to be slightly acid in reaction and probably contains a digestive ferment. In Arcella and in other Thecamoebida vacuoles containing a gas are found within the shell. These vacuoles serve hydrostatic functions. veproduction— Fission. —Reproduction by fission has been proved to occur as a normal process in many of the genera of Lobosa. In Amoeba and allied genera the result of fission is a pair of equal-sized daughter o Fia. 8 Dactylosphaera polypodia, M. Schultze, in three successive stages of division. The indicated occupied fifteen minutes. a, nucleus; b, contractile vacuole. (After F. Schultze.) Amoebae. In Pelomyxa, Trichosphaerium, and probably in other multinucleated Gymnamoebida, fission may be unequal. In the Thecamoebida one of the individuals of the act of fission retains the shell, and the other sooner or later forms a new shell — which is usually larger than that of the parent. THE LOBOSA rf The process of fission is usually preceded by division of the nucleus, or in the binucleate Amoebae of both nuclei. In some species (Amoeba binucleata and Paramoeba eilhardi, Schaudinn (Figs. 4 and 5), 4. limax, Vahlkampf, and Amoeba proteus, Awerinzew ) the division of the nucleus shows some of the charac- ters of ordinary mitosis. The chromatin is collected together into a large number of short chromosomes arranged in an equatorial row. They then divide and travel in two equal parties along faintly stained and nearly parallel lines, supposed to be of the nature of linin, towards the opposite poles of the nucleus, where they unite to form the chromatin network of the daughter nuclei. The threads of the figure do not always converge at the poles to a focal point, and as a general rule it is doubtful whether structures exactly similar to the centrosomes of the metazoan nuclei occur. Centrosomes, however, have been described and figured in the division of the nuclei of Pelomyxa (Bott [2], Fig. 11, a). Notwithstanding the evidence of a primitive kind of mitosis in the division of the nuclei in these and other species, the division of the nucleus of Amoeba crystalligera, of A. hyalina, of Dactylosphaera polypodia, and of Endamoeba coli (Schaudinn) is amitotic. In Pelomyxa and Trichosphacrium fission usually consists in the pinching off of globules from the body, each containing a few nuclei. These globules rapidly assume the characters of the parent; they increase in size and the number of the nuclei is augmented. This process may be regarded as a case of unequal fission or of gemmation, but it appears to differ from the equal fission of some species of Amoeba in the respect that antecedent division of the nuclei is not an essential preliminary to division of the cytoplasm. In a large multinucleate form of Amoeba proteus, Stolé (31) has found that division of the nuclei may or may not take place before fission; and in some cases some of the nuclei divide and others do not before an act of fission. Encystment and Spore-Formation.—It is now known that many of the Gymnamoebida periodically undergo a process of encystment in which the pseudopodia are withdrawn, the body becomes more or less spherical, and one or more tough membranes are formed which entirely surround and protect the animal. In some cases these cysts appear to be of the nature of resting cysts (Amoeba limaz, Vahlkampf [33]), the organism emerging from the broken cyst-wall with the same characters it possessed previous to cyst- formation.. The formation of resting cysts probably occurs in all the Thecamoebida. In many cases, however, the encystment is accompanied by complicated nuclear changes and divisions followed by division of the cytoplasm, and a swarm of minute spores that are often very different in character from the parent form are hatched out when the cyst-wall breaks down. 74 THE LOBOSA In the case of Endamoeba coli (Schaudinn [36]), for example, the uninucleate amoeboid form discharges all foreign bodies from its cytoplasm and becomes surrounded by a clear, soft, jelly-like envelope. Within the cyst-wall it divides into two equal parts each with a single nucleus, and these two parts remain separate for a considerable time. The two nuclei then fragment, their chromatin being scattered in the cytoplasm as isolated chromidia. The two nuclei are now reconstructed, but each reconstructed nucleus is relatively poor in chromatin. Each of these nuclei now divides into two by a primitive kind of mitosis; one of them from each half-amoeba is rejected as a polar nucleus and the remaining one divides again. At this stage in the process the protoplasm contracts, the gelatinous membrane disappears, and the cyst is surrounded by a harder membranous wall. The daughter nuclei of this mitosis conjugate reciprocally with the daughter nuclei of the other half-amoeba, and each of the two zygote nuclei thus formed divides twice. The eight nuclei thus formed become the nuclei of eight amoebulae which escape from the cyst. In Amoeba proteus also, according to Scheel, division of the nucleus and cytoplasm takes place during the encystment, and A Fic. 9. B A, cyst of Amoeba proteus ; abe, cyst-wall; d, gelatinous envelope; 2, F, nuclei; G, albu- minous bodies. x 300. (After Scheel.) B, cyst of Hndamoeba blattae, with 25 nuclei. (After Schubotz.) a swarm of small amoebulae emerge from it when the cyst breaks down. In this case, however, there is no evidence that any form of nuclear conjugation takes place during the encystment. Conjugation.—Although the complete life-history of only a few species of the Lobosa has, at present, been fully worked out, the evidence is accumulating to justify the conclusion that a process of conjugation is an essential condition for the completion of the life- cycle in all forms. The process of conjugation has not yet beem observed in Amoeba proteus or in any of its allies. Nuclear con- jugation accompanied by fusion of the cytoplasm occurs during. encystment in Lndamoeba coli. THE LOBOSA 75 In Pelomyxa (Bott [2]) amoeboid isogametes are discharged from the body with a nucleus formed in a manner that suggests that the number of the chromosomes is reduced (infra, p. 76). These gametes conjugate to form a zygote (Fig. 10), which may subsequently encyst. In Trichosphaerium (Schaudinn [26]) a large number of biflagellate isogametes escape from the cyst and by exogamous conjugation form zygotes which become amoeboid in character. Biflagellate isospores arise from the cystic stage of Paramoeba eilhardi, but there is no evidence, at present, to show that they conjugate. In Centropyzis (Schaudinn [27]) heterogametes are formed which have a shell. After conjugation the zygote escapes from the shell and forms a new one like that of the adult individual. Life-History.—The recent rapid advance in our knowledge of the life-history of Lobosa, due in large measure to the researches of Schaudinn and R. Hertwig, suggests that in all cases the developmental cycle that is passed through is both complicated and varied. In order to illustrate the general character of these life- histories, four examples may be taken for description. Endamoeba coli is found in the upper part of the human large intestine, but unlike Hndamoeba histolytica it does not appear to be the cause of or associated with any particular form of disease. It undoubtedly occurs in perfectly normal and healthy hosts. During the ordinary vegetative life in the intestine it multiplies by simple fission with amitotic division of the nucleus. Occasionally schizogony occurs, when the nucleus divides into eight by successive mitoses and each of these nuclei becomes the nucleus of a daughter amoebula. After a certain period of vegetative life, the normal duration of which has not been estimated, the uninucleated amoebae become encysted, and in that condition are passed into the lower part of the large intestine, and so to the exterior with the faeces. The complicated divisions and the conjugation of the nuclei during and antecedent to complete encystment have already been described. Many of the cysts undoubtedly perish, but the cysts with eight nuclei when swallowed by another host will give rise to eight amoebulae which infest the intestine of the new host. The cysts with more than eight nuclei that are sometimes found in the faeces are, according to Schaudinn, degenerating cysts, and never give rise to active amoebulae. In Trichosphaerium, a marine rhizopod with peculiar radiate pseudopodia and many nuclei, there are two phases in the life-cycle. In the first phase the gelatinous investment is armed with radiating spicules. It reproduces itself in this phase by simple binary or by multiple fission, the pseudopodia being previously withdrawn. In 76. THE LOBOSA the second phase, in which the radiating spicules do not occur, — reproduction may also occur in a manner similar to that of the first phase, but at the conclusion of vegetative growth the pseudopodia are withdrawn, all foreign bodies and excreta are expelled, and a cyst is formed. The nuclei then divide rapidly by repeated mitoses to form an immense number of minute nuclei. These nuclei become the nuclei of minute biflagellate swarm-spores (gametes), which escape from the gelatinous investment of the cyst, and after conjugation give rise to small individuals of the first phase. In Pelomyxa, a multinucleate freshwater rhizopod (Fig. 14), repro- duction is effected by simple or multiple fission during the vegetative period of life, but at certain times, after a complicated series of nuclear divisions in which a re- duction in the number of chro- mosomes occurs, uninucleated, heliozoan-like swarm-spores escape we Nee which conjugate to form a zygote, Zygote of Pelomyxa palustris. a, encysted. and this ramxes sts. From the & st _ 0, after escape from the cyst. (After Bott.) g uninucleated amoebula escapes, which by growth and multipli- cation of the nucleus gradually assumes the typical Pelomyxa form. In the preparation of the nuclei for the formation of the gametie nuclei, a considerable part of the chromatin is discharged into the cytoplasm, and from that which remains eight chromosomes are formed on the equatorial band of a central spindle (Fig. 11, a). Two successive divisions take place, the first of which is regarded as a reduction division, and the second as an equation division. The chromatin of the four chromosomes of this last division collect together in two lumps, and a transparent globular vacuole appears in their immediate neighbour- ae: hood. This vacuole gradually op ‘the reduction division with’ eight. elmomo- fills with minute granules apeire 2b, the gee 4 of = a a : ‘ . : 4 in a clear vacuole. ch, the chromatin lumps which rapidly increase in size the last nuclear division. (After Bott.) and gives rise to the nucleus of the gamete (Fig. 11, »). The chromatin lumps at the same time dwindle and eventually disintegrate. In Centropyxis, one of the Thecamoebida, binary fission oceurs by the protrusion and division of the protoplasm preceded by amitotic division of the nucleus. One portion of the divided proto- plasm with one nucleus returns to the old shell, the other forms a new shell but of a larger size. It does not seem certain whether Fic. 11. THE LOBOSA 77 the individual retained by the old shell is or is not capable of further reproduction, but the occurrence of an immense number of empty shells in cultures of Centropyzis and its allies suggests that it may die after one act of fission. ‘The individual that has formed a new and larger shell, however, certainly divides again, giving rise by a similar process to a daughter individual with a still larger shell. When by these processes of fission the full size is reached, the nucleus degenerates, after giving rise to an expanded chromidial network which, with about two-thirds of the protoplasm, protrudes from the mouth of the shell, is pinched off, and escapes. The remaining one-third of the protoplasm and the degenerate nucleus that remain in the shell probably die. The escaped protoplasm may give rise to one of two broods of gametes. In one brood (the megagametes) the chromidia give rise to a nucleus and the protoplasm forms a shell; in the other, after a nucleus is formed from the chromidia and a shell is formed as in the first brood, a division into four individuals (the microgametes) takes place, and each of these escapes and forms a small shell. Conjugation takes place between the larger and smaller individual gametes, and the zygote escapes to form a new shell like that of the parent. ORDER Gymnamoebida. The surface of the body either naked or provided with a thin flexible membrane through which the pseudopodia can be protruded. Genera -Amoeba.—The generic name Amoeba is often applied to any naked amoeboid organism without reference to its subsequent or antecedent history. As our knowledge of the natural history of the simpler Protozoa widens it becomes more evident that the generic name should be used only in a restricted sense. The limits we place upon the use of the generic name can only be regarded as provisional. Further investigations may well prove that the species now included in the genus Amoeba ought to be still further separated into subgeneric or generic groups. The characters of the genus may be summarised as follows :— Solitary Gymnamoebida, with a few short blunt pseudopodia, a single contractile vacuole, and one or more nuclei. No membrane covering the body in the trophic phase of life. Freshwater or marine. Nine or ten distinct species have been described from fresh water in this country (Cash). They are usually found in the mud at the bottom of ponds or creeping on submerged vegetation. Some of the rarer forms are found in Sphagnum bogs. One of the commonest species is Amoeba proteus (Fig. 12, 5), a species capable of considerable variation in form, but usually exhibiting several —-. 78 THE LOBOSA digitiform pseudopodia. In this species there may be either one or many nuclei. It may reach a size of 200, in diameter. A. guttu v (Fig. 12, 4) is another very common species of small size, 30 p, which shows slow undulating movements of the ectoplasm but rarely protrudes definite pseudopodia. In Amoeba limax (Fig. 12, 2), which is slug-like in form, the end that is posterior in progression shows a fan-shaped arrangement of short ridges, due probably to the Fic. 12. . Different species of freshwater Gymnamoebida. 1, Dactylosphaera radiosa, X 260. 2, — Amoeba limax, x 200. 3, Amoeba verrucosa, x 200. 4, Amoeba guttula, Duj., regarded as a form of A. proteus by Leidy. 5, Amoeba poe 6, Amoeba (Owramoeba) vorax, X 130. nucleus ; ¢.v, contractile vacuole; F.v, food vacuole ; F, hyphae ofa fungus. In ‘Amoeba vorae some of the large diatoms (D, D) upon which it feeds and the ae ee positions of the — nucleus and contractile vacuole are shown. (1, 2, 8 from Cash; 4, 5, 6 from Leidy.) wrinkling of the surface in the vortex of the retreating axial sr (see p. 69). : The marine Amoebae have not yet been carefully recorded. Amoeba crystalligera is often found in marine aquaria, and as allied to the freshwater 4. gullula has been found at Woods Hole in America. Amoeba fluida was found in sea-water aquaria in — Freiburg by Gruber, and this with two other species were also — found by him in the Gulf of Genoa. ‘Ss THE LOBOSA 79 It may be regarded as extremely doubtful whether the forms that the Amoebae present really indicate true differentiation into definite species, or represent the varying influence of certain ex- ternal conditions acting upon one species, or, again, represent different phases in the life-history of one or more distinct species. Thus it has been observed that when the amoebae found on the surface of decomposing hay infusions are placed upon a slide, broad lobate pseudopodia begin gradually to be extended in various directions and the general form of Amoeba proteus is assumed. After a time, when progression may be induced in one direction, the body becomes elongated and more or less pointed at the anterior end, so that the form becomes similar to that known as Ad. limaz. If the water be made very feebly alkaline the amoebae contract into a spherical shape with very short dentate pseudopodia, similar to 4. guttula, and then protrude long pointed pseudopodia similar to those of Duactylosphaera radiosa.* The forms usually attributed to the genus Owramoeba, Leidy, have been shown to be Amoebae in which fungal filaments are growing (Poteat [21]). The filaments arise from spores which are always situated in the neighbourhood of the contractile vacuole. It has been suggested that the fungus receives nourishment from the waste products of the amoeba. These filaments have been observed in Amoebae attributed to the species 4. villosa, A. binucleata, and A. proteus. The life-history of no species of Amoeba has yet been fully worked out, but Calkins (7) has shown that Amoeba proteus normally passes through an early stage when the pseudopodia are relatively long and more pointed and similar to those of 4. radiosa ; and Scheel (29) has proved that the uninucleate condition is succeeded by a multinucleate condition previous to encystment. Calkins suggests that the life-cycle of Amoeba proteus may be somewhat as follows:—The zygote gives rise to a small radiate form, which develops into the uninucleate type-form. This encysts and by schizogony gives rise to uninucleate Amoebae, which develop into the multinucleate type-form. The multi- nucleate type-form encysts and gives rise to the gametes, which conjugate to form the zygotes. Paramoeba, Schaudinn. Several radiating pseudopodia. A well- defined chromatin body is present in the cytoplasm close to the nucleus. Swarm-spores with two flagella. P. eilhardi was found in a marine aquarium in Berlin. 10-90 p. P. hominis, a human parasite (p. 83). Dactylosphaera, Hertwig and Lesser (Fig. 12, 1), is distinguished from Amoeba hy the numerous rigid ‘pseudopodia, which do not completely retract when at rest. Freshwater. Maximum 120 up. ES EEE ER SE SD Ta ar ee 1 Verworn, General Physiology, English translation, 1899, p. 184; and Doflein, F., Archiv Prot. Suppl., 1907, p. 250. 80 THE ELOBOSA Lithamoeba, Lankester 1 (Fig. 13). Body discoid, pseudopodia lobular and hernia-like. A distinct pellicle covering the body, which ruptures for the protrusion of the pseudopodia. Freshwater. Maximum 125 p. Dinamoeba, Leidy. Pseudopodia long, conical, and acute. Body enveloped in a delicate hyaline jelly bristling with minute spicules. Bogs of New Jersey. 60-160 p. The following genera were described by Frenzel (8, 9) from fresh water in the Argentine Republic: Chromatella, Stylamoeba, Saltonella, and Ezkenia. Centrochlamys, Claparéde and Lachmann. The body covered with a thin, membranous, disc-shaped test through which the pseudopodia pro- Fia,. 13. Lithamoeba discus, Lank. A, quiescent; B, throwing out pseudopodia. c¢.v, contractile vacuole, overlying which the vacuolated protoplasm is seen; cone, concretions insoluble in dilute HCl and dilute KHO, but soluble in strong HCl; f, food particles; n, nucleus. (After Lankester.) trude. No definite pylome. A single nucleus and several contractile vacuoles. Freshwater. 40-45 p. | Amphizonella, Greeff. Probably closely related to Centrochlamys. The body is usually invested by a supple membrane which, under some circum- stances, is itself surrounded by a transparent mucilaginous envelope. The pseudopodia are pushed through these membranes and withdrawn again without leaving any definite aperture. It has not been deter- mined whether the position on the test through which the pseudopodia protrude is definitely fixed or varies. These two last-named genera are undoubtedly closely allied to Corycia, Cochliopodiwm, and other Thecamoebida. Hyalodiscus, Hertwig and Lesser. The ectoplasm usually very thick, and sometimes exhibiting radiating lines. A creeping movement with- out pseudopodia frequently occurs. One or more inconspicuous nuclei. Freshwater. 40-60 p. Trichosphaeriwm, Schneider. The structure and life-history of this genus has been fully described by Schaudinn (26). The body is in- vested by a gelatinous test perforated by many pores for the protrusion 1 Lankester, Q. J. Micr, Sci. xix., 1879, p. 484. THE LOBOSA 81 of long digitate pseudopodia; several nuclei; no contractile vacuoles. Zooxanthellae occur in the protoplasm. Marine. Pelomyxa, Greeff. A remarkable genus of Gymnamoebida found in the mud of ponds and ditches, and distinguished by the presence of an enormous number of minute nuclei. Several species have been described. P. palustris, Greeff, P. villosa, Leidy, are frequently found in this country and are probably cosmopolitan. P. penardi, Rhumbler (22), was found at Gottingen. P. viridis has only been found in British India. They vary considerably in size, but when spread out in progression P. viridis may attain to a size of 8 mm. in diameter, and the other species to 2 mm. The form of the animal is like that of an amoeba, and progress is effected by means of numerous blunt lobose, viliform, or some- times attenuate and anastomosing pseudopodia of very variable form and length. There is neither test Fic. 14. nor enveloping membrane. _Pelomyxa palustris, Greeff. An example : 5 with comparatively few food particles. (After In the ordinary vegetative con- Greeff.) dition of Pelomyxa there are very many nuclei. Bourne (3) calculated that in a large specimen of P. viridis there may be 10,000 nuclei. In addition to the nuclei there are numerous minute scattered chromidia (Bott [2]) (Fig. 7). These chromidia may be clearly seen in the ectoplasm. The chromidia are formed by the chromatin discharged from the nuclei, and they never unite to form a chromidial network. In addition to the nuclei and chromidia, the cytoplasm contains refringent bodies of a proteid nature (Veley [34]), numerous symbiotic bacteria, food-vacuoles, and various water-vacuoles, and minute vesicles. The refringent bodies appear to be waste materials and probably a by-product of metabolism, and are undoubtedly used as the food material of the symbiotic bacteria. They are sometimes ejected from the body, but in general the Pelomyzxa relies on the bacteria as scavengers to clear its protoplasm of these bodies. The life-history of the symbiotic bacteria (Cladothriz pelomyxae) has been studied by Veley, who also determined the proteid nature of the refringent bodies by obtaining the characteristic reactions with—(1) Millon’s reagent; (2) sugar and sul- phuric acid; (3) the xanthoproteic test; and (4) with caustic soda and copper sulphate. The green vesicles described by Bourne in P. viridis appear to be of the same nature as the refringent bodies, but stained with chlorophyll. The protoplasm of all the species contains a number of vacuoles and vesicles, but none of them appear to be rhythmically contractile. 82 THE LOBOSA Endamoeba.1—The species of this genus are parasitic in the intestines of various animals. There is no contractile vacuole, and rarely more than one short pseudopodium is protruded. Hndamoeba coli is commonly found in the human intestine. It is often present in perfectly normal health, and is not associated with or the cause of disease. The size does not exceed 50 u. Endamoeba histolytica is so similar in size and form to £. colt in some stages of its life-history that it has been regarded as the same species, but it is now known to have a different life-history and to be the active cause of certain forms of tropical dysentery. It is found not only in the ulcers of the intestinal mucous membrane, but also in abscesses of the liver accom- panying the disease. It penetrates the mucous membrane of the intes- tine and enters the submucosa (Dopter [ 42)). Fic. 15. The life-history of Hndamoeba nucleus in the resting condition, ba /stolytica has not yet been fully specimen with two nuclei. (After Casa- worked out. It is very similar grandi and Barbagallo.) : - e in size and appearance to J. coli, but differs from it in the somewhat indefinite and variable character of having usually a more distinct hyaline ectoplasm. According to Lesage (43) the large cysts, similar to those of £. coli, 20 » in diameter, are never found in this species. In E. histolytica the cysts are 3-6 »in diameter. During the progress of the disease which it causes it is constantly changing its shape and position, and asexual reproduction proceeds rapidly by simple fission or multiple gemmation. Cyst-formation only begins when healing commences, never in the height of the disease. The encystment is preceded by the rapid discharge of chromidia into the cytoplasm, and then the nucleus degenerates and disappears. The chromidia then collect to form a chromidial network in the ectoplasm, and subsequently spherical bodies, the cysts, each surrounded by a yellowish-brown membrane and containing a portion of the chromidial network, are pinched off (Fig. 16, D). The rest of the life-history has not been followed, but it has been shown that when the cysts are given to cats they cause a dysenteric disease. Other species of Endamoeba have been described from the human intestines, but it is uncertain at present whether they are or are 1 The account given of Hndamoeba coli and LE. histolytica is mainly taken from the important memoir of Schaudinn. This memoir is, however, not illustrated. For further information and for figures of Hndamoeba coli the reader is referred to the memoir by Casagrandi and Barbagallo (38), and of EZ. histolytica to the memoir of Jiirgens (39) and other papers mentioned in the list of literature on p. 92, a: THE LOBOSA 83 not associated with disease. Hndamoeba wndulans, Castellani (40), exhibits a peculiar amoeboid form, which occasionally protrudes a single pseudopodium. ‘There is practically no distinction between the ectoplasm and endoplasm. ‘The presence of a peculiar undulat- ing membrane running round one end of the body suggests that the species may have different affinities to the ordinary species of Endamoeba, 25-30 p. Ceylon. Hndamwoeba iurai, Ijima (12), has been described from the human intestines in Japan. The species described under the name Paramoeba homims by Craig (41) was found in the faeces of patients suffering from Fic. 16. Endamoeba histolytica, Schaudinn. A, B, two specimens from a case of dysentery in a cat ; ec, blood corpuscles being digested; N, nucleus, (After Jiirgens.) C, specimen from human intestine with resting nucleus (NV) and a single non-contractile vacuole. D, specimen giving rise by gemmation to a spore; ch, chromatin of nucleus in the form of scattered chromidia ; sp, protoplasm of spore containing some chromidia. (C and D after Lesage.) severe diarrhcea in the Philippine Islands, associated with JZ. histolytica and other Protozoa. ‘There appear to be three phases in the life-history: (1) an amoeboid phase, 15-25 »; (2) a resting cystic stage, 15-20 »; (3) a biflagellate phase, 3-15 ». Notwith- standing the general resemblance in its life-history to that of the marine Paramoeba eilhardi, it is difficult to believe that this species is rightly placed in the same genus. Eindamoeba blattae is often found in the rectum of the common cockroach. In form it is similar to Amoeba limaz, but it seldom pushes out a single pseudopodium and has remarkably clear proto- plasm. It may be as much as 80 pw in diameter. Other species probably belonging to the same genus are found in the intestines of mice and in the rectum of the frog. 84 THE LOBOSA It is difficult to determine at present the true nature of many of the amoeboid cells found in the pus and other fluids of patho- logical conditions, but the following are regarded as parasitic organisms: Amoeba urogenitalis, Amoeba kartulisi, Amoeba buccalis. Leydenia gemmipara is an amoeboid cell originally found by Lieberkiihn in the ascites fluid of malignant tumours. The endoplasm contains numerous fat spherules, remnants of red and white corpuscles, and numerous crystalline bodies. The most remarkable feature of Leydenia, however, is the presence of a -definite contractile vacuole. Plastogamy frequently occurs, and reproduction is effected by fission and gemmation. There seems to be little doubt from the researches of Schaudinn that Leydenia is an in- Fic. 17. dependent organism, but whether it should be placed Endamoeba blattae. : : : 2 N, nucleus: b, bac. With the Lobosa or with the Myxomycetes is not teria; c, at the an- clear. terior pole granules are seen arranged in : the direction of the ORDER Thecamoebida. protoplasmic cur- ; k Sep ——— The body is protected by a shell or test, which may be perforated by a hole—the pylome—or widely open on one side like a cap. The test is not perforated by the pseudopodia. The test of the Thecamoebida is composed of two sheaths— an inner sheath, which is in the form of a thin continuous layer ; and an outer sheath, which is usually much thicker, and may be strengthened by the secretion of definite hard plates or by the adhesion of foreign materials of various kinds. The chemical constitution of the test is difficult to determine with accuracy, but it appears to consist of an organic matrix usually containing silica in larger or smaller proportions. The inner sheath of the test contains a small proportion or only traces of silica; the plates and prisms of the outer sheath, such as we find in Quadrula and its allies, contain a much larger proportion of silica. The matrix which cements the plates of Quadrula together, and which fastens diatom shells, grains of sand, and other foreign bodies to the test of Difflugia, is an organic substance which also contains a trace of silica. In the plates of Quadrula irregularis calcium appears to take the place of silicon. There is no evidence of the occurrence of chitin in the tests of any Thecamoebida, but a substance allied to keratin may occur in some cases (A werinzew [1 ]). In the Cochliopodiidae the shell is thin and flexible. It is usually marked by minute punctuations arranged in definite rows or more irregularly distributed. When more highly magnified THE LOBOSA 85 these punctuations appear to be globular in shape, but their precise nature has not yet been determined. In Quadrula the outer sheath consists of a series of square plates cemented together by the matrix. These plates can be raised to & high temperature without destruction of their form. When boiled for a long time in 10 to 20 per cent KHO, they are dissolved but leave behind a fine granular residue which probably represents the inorganic components of the plates. In Nebela the plates are discoidal, and in other genera irregular in form. The diatom or desmid shells, the grains of sand or glass, and other foreign bodies that are found fastened to the outer sheath of the test of Difflugia (Fig. 20) and its allies are not adventitiously placed, but are caught and definitely arranged in position by the animal (Rhumbler). There can be little doubt that Diflugia exercises a deliberate choice of the particles it uses for shell purposes, and to a certain extent the character of the foreign particles and their arrangement can be used for racial or specific distinctions. In the Arcellidae the outer sheath is composed of hexagonal or irregular prisms (Fig. 18), some of which, situated at regular intervals, are rather longer than the others and project on the surface as round knobs or bosses. 9 ee Og The prisms are cemented together by an extremely Rie 18. thin matrix. Section through the The cytoplasm of the Thecamoebida is often {3° prandia showing the hexagonal plates, arranged in three zones. The cytoplasm of the some of which project at irregular intervals pseudopodia and of the region of the pylome is as shallow bosses on usually remarkably hyaline and the granulations baa ihe extremely fine. In the middle zone it is more coarsely granular, and contains the contractile vacuoles, food- vacuoles, crystalline bodies, excreta, oil-globules, etc. In the zone next to the fundus of the shell is usually found the nucleus or nuclei and the sickle-shaped or more irregularly disposed chromidial network. In the Arcellidae, however, the arrangement is somewhat different from this (p. 86). The pseudopodia are probably subject to considerable variation in shape and number according to external conditions. In the Difflugiidae there may be only one long finger-like pseudopodium extended to a length double that of the shell, or there may be three or four shorter pseudopodia, or occasionally as many as seven protruded at the same time. In Leleopera the number of pseudo- podia appears to be constantly more numerous than in other genera of the family. In some species of Arcellidae and Cochliopodiidae a membranous expansion of the cytoplasm sometimes protrudes from the pylome. Very little is known concerning the contractile vacuoles of the Thecamoebida, as the thick opaque test interferes considerably with 86 THE LOBOSA the observation of it in the living animal, but it seems probable that one or more contractile vacuoles are present in all genera. Nucleus.—For a considerable period in the life-history of Arcella there are two large oval nuclei, from 0°015-0°02 mm. in diameter, which are usually situated some distance apart, near the periphery of the cytoplasm. More rarely three or even four of these relatively large nuclei may be found. These nuclei are derived by the karyokinetic division of the primary single nucleus of the young Arcella. Each nucleus contains a single large (008 mm.) nucleolus, which apparently consists mainly of chromatin, but is otherwise clear and transparent (Fig. 21). In other Thecamoebida (Difflugiat and Centropyzis) there is usually only one nucleus during the corresponding phase of the life- history, and this exhibits a coarse reticulum of chromatin with numerous nucleoli distributed through it. The chromidial network of Arcella is in the form of an irregular band or ring at the periphery of the cytoplasm, which sends lobate processes or branches in the direction ‘of the central protoplasm. These processes are sometimes pinched off from the peripheral ring, and appear as isolated patches of the chromidial network in the central cytoplasm. ° ) In Centropyxis the chromidial network is in the form of a thick sickle-shaped band lying in contact with the convex aboral extremity of the body. Sometimes this band envelops the nucleus, but neither in Centropyzis nor in Arcella does the nucleus come into contact with the network, being always surrounded by a halo of clear protoplasm (Fig. 21). In some forms of Diffllugia the chromidial network is in contact with the nucleus (Fig. 6) ; in D. globosa and others, however, there is a clear space between the nucleus and the chromidial network as in Centropyzis, but in these cases strands of the chromatin seem to connect the nucleus with the network. In another phase of the life-history of , it Nsw} EN ~~ eee Na © UC Fie. 2. The development of isopores and heterospores in Thalassicolla nucleata. (After Brandt, 1905.) A-C, isospore-formation, x100. The large nucleus (N) breaking up into spore nuclei (N. Isp). D, an isospore (x 2000); Cone. stratified concretions lying in proteid vacuoles. E-K, hetero- spore-formation, x 100. E, nuclear membrane collapsing. Nuclear figure and one intra- nuclear centrosome. F, diffusion of nucleoplasm (Nm) outwards. G, organisation of second- ary nuclei (No). H and K, segregation of these nuclei to form heterospore nuclei. LL, mega- spores. This figure shows the two flagella arranged like those of a Dinoflagellate. M, micro- spores. L, M, x 1000. 101 102 THE RADIOLARIA horizontally and is coiled round the body of the spore, the other projects freely outwards and backwards. Consequently, as these minute structures dart or vibrate, they rotate unceasingly about their long axis, the whole mechanism and display recalling those of certain Peridiniae. The further history of the iso- and heterospores is unknown. Brandt’s recent attempts (26) to obtain conjugation between spores of the same and of different individuals have been as futile as those of earlier observers. If, however, we may judge by the analogy of other Protozoa, and in particular by the life-history of T7icho- sphaerium (Schaudinn [42]), we may presume that the heterospores are male and female gametes, and that the isospores are asexual indi- viduals. But on this question, as on the further one of a suggested alternation between isosporous and heterosporous generations of Thalassicolla, we still lack information. Fie. 3. 1, central capsule of Thalassicolla nucleata, Huxley, in radial section, x 100; a, the large nucleus (Binnenblischen); 6, proteid vacuoles of the intracapsular protoplasm con- taining concretions; c, wall of the capsule (membranous shell), showing the fine radial pore- canals; d, chromatin substance of the nucleus. 2, 3, Collozowm inerme, J. Miiller, two different forms of colonies, of the natural size. 4, central capsule from a colony of Collozoum inerme, showing the intracapsular protoplasm and nuclei, broken up into a number of isospores, each of which encloses a crystal of strontium sulphate; c, yellow cells lying in the extracapsular protoplasm. 5, a small colony of Collozowm inerme, magnified 25 diameters; a, alveoli _ (vacuoles) of the extracapsular protoplasm ; b, central capsules, each containing besides proto- plasm a large oil-globule. 6-13, yellow cells of various Radiolaria. 6, normal yellow cell; 7, 8, division with formation of transverse septum; 9, a modified condition according to Brandt ; 10, division of a yellow cell into four; 11, amoeboid condition of a yellow cell from the body of a dead Sphaerozoon ; 12, a similar cell in process of division ; 13, a yellow cell the protoplasm of which is creeping out of its cellulose envelope. 14, Heliosphaera inermis, Haeck., living example, x400; a, nucleus; b, central capsule; c¢, siliceous basket- work skeleton. 15, two isospores of Collozoum inerme, set free from such a central capsule as that drawn in 4; each contains a crystal b and a nucleus a. 16, two heterospores of Collozowm inerme, of the second kind, viz. devoid of crystals; and of two sizes, a megaspore and a microspore. They have been set free from central capsules with contents of a different appearance from that drawn in 4. a, nucleus. 17, Actinomma asteracanthion, Haeck., x 260; one of the Peripylaria. Entire animal in optical section. «a, nucleus; 6, wall of the central capsule ; innermost siliceous shell enclosed in the nucleus ; cl, middle shell lying within the central capsule ; c2, outer shell lying in the extracapsular protoplasm. Four radial siliceous spines, holding the three spherical shells together, areseen. The radial fibrillation of the protoplasm and the fine extracapsular pseudopodia are to be noted. 18, Amphilonche messanensis, Haeck., x 200; one of the Acan- thometrida. Entire animal as seen living. (After Lankester.) Cuier MODIFICATIONS OF STRUCTURE IN THE RADIOLARIA. The Radiolaria may be derived from such an organism as Thalassicolla by—(1) fission and the formation of a colony of similar or dimorphic individuals imbedded in a voluminous communal jelly (Sphaerozoa or polyzoic Radiolaria) ; (2) by differentiation of the openings of the central capsule from its evenly porose condition (Peripylaria) to a radially segregated oligo-porose type (Acantharia), to a single pore-plate at one pole of the now asymmetrical capsule (Monopylaria), or to a single main aperture and two lateral ones (Tripylaria); (3) by differentiation in the ectoplasm of skeletal spicules and shells of the most diverse forms, which only in the Acantharia invade the endoplasm. 104 THE RADIOLARIA Amongst the most primitive Radiolaria are the Physematiidae and the allied families Thalassicollidae, Thalassophysidae, etc. In all these forms the hydrostatic jelly is so well developed as to give the term Collodaria to the order formed by them. In the first family, however, the vacuoles elsewhere found in the ectoplasm are endoplastic products, no stratified nutritive concretions are found, and yellow cells are absent. The skeleton, if present, consists merely of scattered spicules. These organisms belong to the surface strata of the ocean and are phosphorescent. Their life- history falls into well-marked nutritive and reproductive phases. The early nutritive stage was erected by Haeckel into a special genus Actissa, which Brandt has shown to be a phase of growth that occurs in at least two of the five families. The later nutritive stage differs in few characters from that of Thalassicolla. The Phy- sematiidae afterwards pass into an isosporous reproductive phase ; Fic. 4. 1, Lithocireus annularis, Hertwig; one of the Monopylaria. Whole animal in the living state (optical section). a, nucleus; 6, wall of the central capsule; c, yellow cells; d, per- forated area of the central capsule (Monopylaria). 2, Cistidiwm inerme, Hertwig; one of the Monopylaria. Living animal. An example of a Monopylarion destitute of skeleton. a, nucleus ; b, capsule wall; ¢, yellow cells in the extracapsular protoplasm. 3, Carpocanium diadema, Haeck.; optical section of the beehive-shaped shell to show the form and position of the protoplasmic body. a, the tri-lobed nucleus ; 6, the siliceous shell ; c, oil-globules ; d, the perforate area (pore-plate) of the centralcapsule. 4, Coelodendron gracillimum, Haeck. ; living animal, complete; one of the Tripylaria. a, the characteristic dark pigment (phaeodium) surrounding the central capsule b.. The peculiar branched siliceous skeleton, consisting of hollow fibres, and the expanded pseudopodia are seen. 5, central capsule of one of the Tripylaria, isolated, showing a, the nucleus; b, c, the inner and the outer laminae of the capsule wall; d, the chief or polar aperture ; e, e, the two secondary apertures. 6, 7, Acan- thometron Claparedei, Haeck. 7 shows the animal in optical section, so as to exhibit the characteristic meeting of the spines at the central point as in all Acanthometrida; a, small nuclei; b, a parasite (Amoebophrya) ; c, wall of the central capsule; d, extracapsular jelly ; e, peculiar intracapsular yellow cells. 8, Spongosphaera streptacantha, Haeck.; one of the Peripylaria. Siliceous skeleton not quite completely drawn on the right side. a, the spherical extracapsular shell (compare Fig. 3 (17)), supporting very large radial spines which are con- nected by a spongy network of siliceous fibres. 9. Aulosphaera elegantissima, Haeck.; one of the Phaeodaria. Half of the spherical siliceous skeleton. (After Lankester.) the Thalassicollidae into either isosporous or heterosporous modes of reproduction ; and the Thalassophysidae fragment suddenly into hundreds of minute pieces (see pp. 137-8), without passing, so far as is known, into a sporulating phase. In the next division (Sphaerozoa) the polyzoic condition is characteristic of the nutritive phase. The colony or coenobium is spherical, elongate, or moniliform, though the individuals may retain the primitive homaxonic symmetry (Collosphaeridae) or become flattened (Sphaerozoidae). The skeleton may be absent, spicular, or spheroidal, and the scattered “nuclei” are homogeneous lumps of chromatin, The life-history of the Sphaerozoa is still incompletely known, though much has been done by Brandt (1885) to follow it. Accord- ing to this writer three kinds of sexual individuals or colonies occur :—isosporous forms, heterosporous forms produced directly, and heterosporous forms produced after gemmation. In the Sphaero- EZ Maa), BIEN Bes ey of nN \ 106 THE RADIOLARIA zoidae both megaspores and microspores arise in the same individual ; isospores in different individuals. Moreover, the asexual individuals are not all alike, but in certain genera at least some produce extra- capsular bodies (pp. 138-9), and those individuals which bud off these structures are, according to Brandt, young forms. These fertile young forms become in many cases heterosporous — the extra- capsular body forming the megaspores, the intracapsulum giving rise to the microspores—but in other cases the extracapsular bud develops into a new central capsule. Consequently we have two forms of heterosporous individuals and one isosporous form, and Brandt suggests that there is an alternation between the hetero- sporous and homosporous individuals. Famintzin, however, has reinvestigated the matter, and finds, in the vast numbers of full- grown colonies that occur in autumn at Naples, some are converted into isospores, some into heterospores, and many have extracapsular bodies. These last colonies divide into small winter ones, the majority of which possess extracapsular buds and develop into heterosporous forms. According to Famintzin there is no alter- nation of generations (13). Whilst the Sphaerozoidae thus either become heterosporous directly, or indirectly after division and the development of extra- - capsular bodies, the Collosphaeridae have no extracapsular buds, and their mega- and microspores develop in separate individuals. The skeleton when present takes the form of a perforated shell, but notwithstanding these differences they are held to be rightly separated from the Sphaerellaria, with which Haeckel formerly united them. The Sphaerellaria include an immense number of solitary chambered forms, the majority of which are spherical, the remainder being elliptical or flattened. Radial bars unite the chambers, but these bars are wholly ectoplasmic, and are never joined at the centre of the endoplasm as in certain Acantharia. The nucleus remains single, but grows with the growth of the individual. The Acantharia form a primitive group of Radiolaria with many interesting distinctive features. They retain homaxonic symmetry, but the pores of the central capsule are less closely set than in the Spumellaria. Through these pores there pass not only the cyto- plasmic bridges between ectoplasm and endoplasm, but also two other radiating structures, namely, stiff pseudopodia (axopodia) and spicules. The latter meet in the centre of the capsule (Fig. 4 (7)), the former surround the centre and alternate with the spicules (Fig. 18), which pass outwards generally in five whorls. These emerge from the ectoplasmic surface at points through which five circles could be inscribed corresponding to the two tropical, two polar, and equatorial lines of the globe. The whole disposition strongly suggests that the radiating | i THE RADIOLARIA 107 spicules have developed by a hardening of the stiff fibre of certain alternate axopodia which formerly met at the centre of the endo- plasm as in Heliozoa, to which group this order suggests other points of affinity. The peculiar nature of these spicules is the distinguishing feature of the order. They are composed, in the best investigated cases, of strontium sulphate (Biitschli, 1906), and not of a chitinoid organic acanthin-substance, as Haeckel supposed. To illustrate the structure of the Nassellarian sub-family. A, Plagonis- cus tripodiscus, H., showing the central capsule (¢c.c) supported by the skeletal tripod. B, Cortina typus, H., showing the tripod and sagittal ring (5) enclos- ing the central capsule, within which are seen the podocone (/p), the nucleus above, and three oil- globules. C, Tve- pospyris cortiniscus, H., to show the formation of the helmet-like type of skeleton from the tripod and sagittal ring. (After Haeckel.) The nucleus is a multiple structure, and the large body frequently mistaken for a nucleus (Fig. 4 (6, 0)) is a Suctorian parasite. The Acantharia frequent the upper layers of the ocean (chiefly from the surface down to 300 metres), and are abundant in Arctic and Antarctic seas as well as in the intermediate zones. The yellow cells that in other Radiolaria are confined to the extracapsulum, occur almost exclusively within the central capsule in the Acantharia. The Monopylaria or Nassellaria include an immense range of forms. In the simplest the central capsule is supported by a siliceous tripod or tetrad spicule, often accompanied by a sagittal ring. 108 THE RADIOLARIA It contains a peculiar cone of doubtful significance (Fig. 5, B, p). The ectoplasm streams out from the capsular pore-plate and forms a dense bubbly mass around this opening. From this point it passes as a thin layer around the capsule, so that the cytoplasm is asym- metrically distributed. These Radiolaria are, in fact, bilaterally symmetrical. Lateral outgrowths from the spicule or sagittal ring give rise to a helmet-like shell or ‘“ cephalis,” in the upper part Fia. 6. Eucyrtidiwm cranioides, Haeck., x 150; one of the Monopylaria. Entire animal as seen in the living condition. The central capsule is hidden by the beehive-shaped siliceous shell within|which it is lodged. of which the central capsule is lodged. The cephalis becomes voluminous and often constricted, producing a vast array of specific, skeletal variety, the whole of which is produced by modification of a single spicule. The nucleus, though often lobed, remains single. Spore-formation is known to occur, but no form of reproduction has been adequately investigated. The bionomics of the group are quite unknown. The Tripylaria or Phaeodaria form another large group, most THE RADIOLARIA 109 easily characterised by the brown, greenish-brown, or black accumu- lation of food material, débris, and resistant “ phacodellae” that lie in the oral half of its ectoplasm ; and they are also signalised by the mode of distribution of the capsular pores. In the majority of genera the endoplasm communicates with the ectoplasm only by a teat-like operculum and a pair of small lateral conical pores (the so-called astropyle and parapyles). In a few cases two astropyles occur, and in at least one genus (Allanticella) only a single pore-plate is present. The skeleton varies greatly in structure Aulactinium actinastrum, H.; a member of the Phaeodaria. ‘After Haeckel, slightly modified.) A, astropyle; C, calymma; WN, double nucleus lying in the endoplasm ; P, parapyle ; Ph, phaeodium. and configuration. It is usually of a tubular nature, and the hollow cylinders are often subdivided by septa. The basis of these tubes, however, is formed by minute aciculate spicules which are surrounded by a gelatinous sheath, and between this sheath and the surrounding ectoplasmic matrix is a thin membrane, which first becomes silicified. This is followed by deposition of silica in the gelatinous sheath, and in this way complex spicules, often with candelabra-like appendages, are developed. A single or double per- forated shell may be present, the surface of which has a peculiar porcellanous appearance and “diatomaceous” structure. In the 110 THE RADIOLARIA most complex Phaeodaria this shell acquires a bivalvular form and carries many peculiar processes (Fig. 32). The nucleus is a large, usually single structure, and undergoes a peculiar kind of mitosis accompanied by the formation of a great number of chromosomes. The development and nature of the spores is incompletely known. A characteristic feature of this order is the absence of the yellow cells that occur almost constantly in the other orders. This negative feature appears to be correlated with the presence of that remarkable and still imperfectly analysed complex, the phaeodium. The researches of Borgert (18) give some ground for thinking that the phaeodellae (see p. 119) are excreta, and if so, the retention of these substances in Radiolaria devoid of ‘“ yellow cells” -lends support to the view, derived from a study of the Turbellaria (Keeble and Gamble [41]), that these symbiotic algae exert a depuratory function. Variation: Dimorphism.—The Radiolaria present three kinds of structural modification. There is the divergent variation about one or more centres that constitutes a “species.” There is racial somatic dimorphism in relation to pelagic or abyssal life. And there is gametic dimorphism both in early and adult stages of life in relation to reproduction. The conception of ‘‘species” in Radiolaria is only gradually assuming a form similar to that held in the case of other Protozoa. Hitherto skeletal characters have been mainly and rigidly employed for the erection of a vast number of specific forms. The larger collections made by Plankton expeditions of recent years have shown that many of these earlier species, and even genera, are either growth stages of one and the same form, fission products _ common to several species, or divergent variations referable to a central “type.” The first kind of variation probably occurs in every Radiolarian and has been recently worked out for several Tripylaria (Immermann). In Aulokleptes flosculus, for example, spicules of three kinds can be met with, each one of which was the basis of a separate species in Haeckel’s classification. It has been shown, however, by Immermann that the spicules pass through two or more forms before arriving at their definitive stage, and may be arrested at an intermediate stage. Further knowledge of the development of the skeleton will undoubtedly tend to diminish the profusion of species. that Haeckel has proposed. But it is not skeletal characters only that are subject to change during growth, Among the Collodaria, in which the spicules are a subordinate feature and in some families entirely absent, the early stages of growth differ so greatly from the later ones as to render their identification a difficult matter and one particularly liable to misinterpretation. Thus the genus Actissa, which Haeckel brought forward as the most primitive of all Radiolaria, has been shown by Brandt (25) to THE RADIOLARIA III be an early stage in species of the two families Thalassophysidae and Physematiidae. Even the presence of developmental stages is not decisive proof that the fertile protoplast or coenobium in question is a final stage in the life-history, since in certain forms?! an early and variable reproductive stage is intercalated between the earliest phase and that of full growth. Fission introduces further com- plexities. The Acantharian genus Litholophus was founded on stages of growth or fission products belonging to other genera ; and the division of the Collozoidae by fission leads to minute forms that might easily be mistaken for young stages, although they are reproductive individuals. We are thus led to the conclusion that Fia. 8. Racial dimorphism in Aulacantha scolymantha, x 26. (After Hicker.) A, deep-sea form; B, pelagic form from Naples, 100 fathoms. C.c, central capsule ; Exo, ectoplasin ; Ph, phaeodium ; R, radial spicules ; Tf, tangential spicules. a knowledge of the life-history is essential to the construction of a permanent classification, and that when this is obtained the species will be groups segregated about their several types. The dimorphism of Radiolaria is of two kinds: somatic and gametic. Somatic dimorphism is at present known only in few instances. It consists in the development of a small race of a widely ranging species in warmer surface water, and of a large race (usually three times the size of the former) in cold and deep water. Associated with these differences of size there is structural diversity. The spicules of the small race are fewer and simpler, the ectoplasm they support is delicate and limp, often sagging between the 1 £.g. Collosphaera (Fig. 15, A). 112 THE RADIOLARIA siliceous appendages. The skeleton of the large race ends in more elaborate constructions, and stretches more tightly the tougher, thicker ectoplasm that covers the animal. Such racial dimorphism is known in Aulacantha scoly- mantha (Fig. 8), Circoporus sea- fuscinus, in Auloscena verticilla- tus, and probably will be found more commonly when looked for. Both races are capable of reproduction, and it is im- probable that they merge into one another, but it is not known whether the mode of reproduction is the same in both. Gametic dimorphism is more general and perhaps uni- versal, but is unaccompanied by any known diversity of A Bees B somatic structure. It is there- Radial spicules of A, ab pai form of Aul wipe sia alge _ is = sertetllaias B, pelagic a (After Hicker.) mor phism of such Foraminifera as Discorbina and Truncatulina, and is signalised by the formation of isospores and of heterospores in distinct and differently constituted individuals. These processes involve the contents of the central capsule and are followed by the death of the ectoplasm. An individual Radiolarian is therefore only a phase in the life-cycle of its race, but the changes which lead up to the formation of isospores are so distinct from those that precede the development of heterospores, and involve such deep-seated nuclear transformations, that it is difficult to believe that similar individuals of any one generation can give rise to both forms of spore. On this ground Brandt has been led to formulate the view that isosporous and heterosporous individuals of any one species belong to alternate generations. Direct evidence of this alternation has not been obtained, and therefore the case of the Radiolaria is on a very different footing from the observed alternation in Foraminifera. Distribution : A, Vertical—The recently published reports of the German Plankton expeditions, though not yet complete, enable us to picture the vertical distribution of the Radiolaria more accur- ately than was formerly possible. The older records were derived from surface townettings and from Ehrenberg’s researches on Radiolarian deposits at varying depths. They represented the group as occurring at all depths, even on the sea-bottom, and as increasing in variety with depth. ‘The more recent exploring ex- peditions give a very different result. From them it appears that be THE RADIOLARIA 113 in Atlantic and Antarctic waters—(1) the majority of Radiolaria occur not deeper than 400 metres; that the Collodaria are .em- phatically surface forms characteristic of the top stratum (0-50 m.) ; (2) that in the next stratum below this (50-400) the great develop- ment of Radiolarian, as also of diatomaceous, life occurs. Here the majority of Acantharia, many Spumellaria, and many Phaeodaria, e.g. Challengeridae, occur; (3) that in the still deeper water, 400- 1000 metres, a still richer Phaeodarian fauna and a few Acantharia are met with, and that beyond this a few remarkable forms range down to 5000 metres. The vertical distribution of the Nassellaria is not yet adequately known, but it probably follows much the same lines as that of the Phaeodaria. B, Horizontal.—The distribution of the class is extremely wide, as is readily understood from their dispersal by the great oceanic currents. Some forms are panplanktonic, e.g. Aulacantha; some are bipolar; many are emphatically warm-water forms; others as characteristically follow cold currents. Such considerations enable us to understand the varying depths at which the same form may occur as its chosen current occupies now a deeper, now a more superficial position in the ocean. The greatest variety of species is met with in equatorial waters, and this fulness extends in diminishing variety north and south for some forty degrees. Then there follows, at least in the northerly direction, as in the case of many other pelagic orders, a barren zone, and finally Arctic waters show a Radiolarian fauna that is rich in individuals though poor in variety, and is apparently greatly inferior to that of Antarctic (Hacker). This mode of distribution explains the comparative poverty of the British Radiolarian fauna. Though the lack of research makes reserve necessary, it seems certain that these waters of the west and north-east coasts of Britain contain only a casual Thalassicolla and a few Acanthometrida, Sphaerellaria, and Phaeo- daria, outliers and stragglers of the rich Gulf Stream fauna. The great northern host passes by the Faroes and off the Hebrides, as the lists, pp. 144-151, show, and in those waters the researches of Murray, Fowler, and Wolfenden have revealed a number of interesting forms. The deposits formed by the accumulation of Radiolarian skeletons constitute a well-known element in the composition of littoral and deep-sea Globigerina ooze and of red clay. They make up certain of the clays, marls, and pumices found in the Miocene deposits of Barbadoes, the Nicobar Islands, and on both sides of the Mediterranean, as at Oran and Tripoli. Siliceous organic rocks of Palaeozoic and of Mesozoic age have been recently discovered in many parts of the world; and microscopical investigations of these rocks have revealed an unsuspected wealth of Radiolaria in them. From the Cambrian age onwards, however, the families and even 8 114 THE RADIOLARIA genera appear identical with those now living. Pre-Cambrian Radiolaria are still doubtful (Hinde [44]). The Sphaerellaria (Poly- cystina) and Nassellaria are the chief contributors, since - the strontium skeletons of the Acantharia are readily soluble, and therefore are unknown in recent deposits or in a fossil state, and the hollow siliceous spicules of the Phaeodaria also appear in- capable of resisting decomposition. Many skeletons formerly identi- _ fied as Radiolarian (such as Dictyota and Mesoscena) are now referred to the Flagellata or to other orders, but the Nassellaria Cyrtoidea form the majority, the Sphaerellaria, Discoidea, and Sphaeroidea the minority, of Jurassic Radiolaria in quartzites and coprolites. In later deposits of Miocene ages this predominance is maintained, but the species found are identical with or closely akin to living forms. Central Capsule-—The cytoplasm of Radiolaria is distinguished from that of other Protozoa by the great development, specialisa- tion, and delimitation of its ectoplasm. The boundary between this peripheral layer and the central nucleated plasma is almost always a distinct one; and the few cases amongst the Acantharia and Sphaerozoa in which no limiting membrane can be traced, serve to show that this separation is the outcome of more primitive, undifferentiated conditions, which the Radiolaria display in early life, to which they revert during fission, and occasionally retain throughout life. © The central capsule is the sign of this plasmic differentiation, and the mark of a Radiolarian. It consists of a single, or in Phaeodaria of a double, porous membrane of either chitinoid or mucinoid nature. Usually the capsule is of such tenuity as to be visible only after the use of reagents, or, as in Thalassicolla, it may be comparatively thick and areolated by the growth of ridges on its inner surface (Hertwig). The shape of the capsule is in general correlated with that of the configuration of the animal. In homaxonic Spumellaria and Acantharia it is spherical; in lenticular and discoid forms it is ellipsoidal. In the bilateral Nassellaria it is elongate, and in the Phaeodaria spheroidal; but in the recently discovered spherical Thalassothamnidae it is lobate or branched (Fig. 10). The consistency of the central capsule, however, is not that usually associated with chitinoid structures. It is capable of extension, and in the concentric Sphaeroidea and Discoidea it is lobate and may enclose the inner shells one after another. In the helmet- shaped Nassellaria it throws out lobes through the basal plate of the shells. During the processes of fission and sporulation the central capsule in all Radiolaria becomes more or less completely dissolved to allow of the separation or escape of the endoplasmic contents. These phenomena show that the capsule is no per- THE RADIOLARIA Li manent excretion, but is composed of a substance capable of adaptation, by growth or dissolution, to changes in the endoplasm. The walls of this structure are perforated by fine pseudopodia that connect the endoplasm with the exterior in the manner severally characteristic of the Peripylaria, Monopylaria, and Tripylaria (pp. 102-9). The evenly distributed or segregated pores of the first group admit not only fine plasmic connections, but in Acantharia they also transmit axopodia and radial spicules. The single pore-plate of the Monopylaria, which, according to | Fie. 10. Cytocladus spinosus. x10. (After Schréder [88].) One of the Peripylaria, to show the branched central capsule (C.c), the radiate single spicule (Sp), and the voluminous ectoplasin supported by the spicular rays. It has been recently found off the coast of Japan. Hertwig, consists of perforated, thickened rods of capsular mem- brane, is not thoroughly understood. In most Nassellaria the pores are, of course, confined to one plate-like extremity of the capsule, but they may be evenly distributed over the basal plate, confined to a peripheral zone, or to three circles, which in 7'ridictyopus project peripherally. Associated with this pore-plate is a peculiar, cone-like, fibrillated structure which projects inwards towards the nucleus (Fig. 5, B, p). According to Hertwig this cone is an invagination of the capsular membrane, and the fibrillae are con- tinuations of those that pass through the pore-plate, on their way to join the endoplasm at the apex of the cone. Biitschli, however, 116 THE RADIOLARIA is inclined to consider the cone as due to the coalescence of axopodia somewhat like those of the Acantharia (9, p. 439). The central capsule of the Phaeodaria possesses well-marked characteristics in its double nature and the presence and structure of its main opening or astropyle and of its two lateral parapyles. The former consists of a teat-like operculum apparently striated on the inner side owing to the septate character of the subjacent endoplasm. ‘The latter are made up of an inner bulb and an outer cone which opens on a prominence. The endoplasm under the bulb is also radially grouped, and in general it may be said, as evidence of the interchange of plasma through the capsular pores, that the endoplasm in their neighbourhood has a striated character. The morphological character of the central capsule is a moot point. Most authors, following Hertwig, hold it to be comparable to the shell-membrane of a Thecamoeba, which, however, Dreyer considers is covered by ectoplasm on both sides. It is possible, on the other hand, that the capsule is a basement membrane peculiar to the Radiolaria, and is a consequence of the differentiation of . their cytoplasm in relation to pelagic life. Until its development is studied the question cannot be satisfactorily answered. Cytoplasm.—The cytoplasm of Radiolaria, though one and con- tinuous, is separable anatomically and physiologically into intra- capsular and extracapsular portions. Flotation and dispersal, nutrition and stimulation are offices that devolve chiefly upon the ectoplasm ; storage and reproduction upon the endoplasm. During the early and nutritive stage of life the ectoplasm is predominantly active, during the reproductive phase the endoplasm is solely operative. Continuity of structure and community of function are expressed by an interchange of protoplasmic and metaplastic granules through and beyond the capsular wall. The ectoplasm consists of four chief layers from within out- wards :—an assimilative zone of dense protoplasm around the capsule, a thick alveolar layer capable of secreting gelatinous and fluid spheres, an enveloping membrane guarding the animal from contact with its environment, and beyond this a fringe of radiating, contractile pseudopodia. This great development is primarily related to flotation. From Brandt’s researches on the hydrostatic function of Radiolaria it is clear that the calymmal gelatinous spheres play the chief part of this office. These spheres he holds. are viscous secretions of the ectoplasm and absorb water from without inwards. The specific gravity of the expressed fluid is, however, such as to point to water saturated with carbonic acid, and as we pass from the inner to the outer zones of this alveolar layer, the spheres are found to become more and more vacuolar, until at the surface they are so tense as to collapse at a touch. THE RADIOLARIA 117 Brandt therefore considers that the outer pseudopodia upon con- tact with certain stimuli (wave-motion and heat) contract and transmit the stimulus to the subjacent alveolar protoplasm. This in turn contracts and the surface vacuoles collapse. When this process has been continued for a certain time the specific gravity of the animal is raised and a slow descent follows. Equilibrium is again established, the vacuoles are re-formed, and the animal rises again to the surface. The calymmal spheres do not, however, monopolise the hydro- static function. The flotation of Radiolaria is determined by extension of its surface as well as by the lowering of its specific gravity, and in this sustentative adaptation the outer pellicle and the skeleton play the chief rédle.. The skeleton of the Acantharia is composed of a radiating series of tent-poles upon which the ectoplasm can be raised and tightened by the elastic filaments that pull up the baggy ectoplasm, which upon inflation by vacuolar water expands, and so raises the animal to a higher zone of water; or again contracts, followed by deflation and sinking of the whole mechanism. Again, in Phaeodaria we have a still more elaborate skeleton, the appendicular parts of which are related to the formation and support of the ectoplastic membrane. In an impressive variety of sustentative adaptations the ectoplasm of Radiolaria deposits silicic acid or strontium sulphate; and the attempt now being made to trace a correlation between the variation of this support, the extent and thickness of the outer membrane, and the density and viscosity of various tracts of water inhabited by widely varying forms, has already met with some success (Hicker [35]). Racial forms occur. Aulacantha scolymantha, for example, only attains a diameter of 2°3 mm. in warm surface waters; its ecto- plastic membrane is soft and its spicules small and simple ; whereas in deep, cold water (400-1000 metres) it reaches 7 mm. and consists of a much tougher envelope supported by more numerous spicules. Circoporus seafuscinus and other Phaeodaria are also dimorphic and exhibit a similar differential relation to the surface and abyssal waters in which they occur. The ectoplasm rarely contains assimilates or other inclusions. Oil-globules, however, occur in the large Collodaria; pigment (blue, black, brown, or red) in the Thalassicollidae, Sphaeroidea, Discoidea, and some Acantharia; and concretions (probably proteid) in some Thalassicollidae. Yellow cells are generally present in the ectoplasm, and the only large division in which they are unknown is that of the Phaeodaria. In the Acantharia, however, they occur almost constantly in the endoplasm. A further account of these cells is given below. The myonemes are peculiar modifications of the basal ends of 118 THE RADIOLAKI/A certain pseudopodia.. They occur exclusively in the Acantharia Acanthometrida, and form circular groups of short, rod-like bodies clustered round each of the radial spicules (Fig. 11). Upon careful examination they are found to connect the ectoplasm with the pseudopodial covering of the spicule and to possess a high degree of contractility. Their form varies accordingly. When expanded the myonemes appear as homogeneous threads ‘006 to ‘013 mm. long. When contracted they not only become shorter (012--02) and thicker, but exhibit in many cases a very distinct cross-striping. They are, in fact, muscular structures comparable 2 Ge: 2 - by 4:0" : “2 Pee a “3:7 : on “2 a one 7 , Po) ee ern M , ; ia: , gt ' e eer ' cd oe. * a = : a ' . 2 ‘ ' Ci Z Fie. -11. Portion of a living specimen of Acanthometron pellucidum, one of the Acantharia, x 900 (after Schewiakoff), to show endoplasm and ectoplasm. The latter consists of vacuolated cytoplasm (/) slung up to the rod (S) by striated myonemes (M), which are inserted into the sheath (Sh) around the rod. In the endoplasm two nuclei (NV) and zooxanthellae (Z) are — seen. with the contractile fibrillae of Gregarines and Infusoria (Schewia- koff [33]), and they serve to raise or lower the hydrostatic, ecto- plasmic apparatus of these Radiolaria, and so to facilitate their ascent or descent. Another cytoplasmic modification of the Acantharia may here be mentioned, namely, the axopodia. They consist of contractile pseudopodia that radiate from near the centre of the endoplasm to the periphery of the animal, and possess an axial fibre around which an unceasing cyclosis of granules takes place. These axopodia differ from the ordinary pseudopodia of the Acantharia not only in their deeper origin but also in their more limited THE RADIOLARIA 119 numbers and cyclical arrangement, and they resemble the peculiar pseudopodia of such Heliozoa as Acanthocystis in all points except in not arising from a centrosome. The peculiar cytoplasmic threads that compose the so-called flagellum of the Discoidea are also in all probability of a similar nature. This flagellum consists of immobile pseudopodia fused into a tapering mass which projects freely at one point of the ectoplasm, and its component pseudo- podia, unlike those of the surrounding calymma, can be traced almost to the centre of the endoplasm. They appear to spring from the nucleus. A peculiar accumulation occurs in the extracapsulum of the Tripylaria, to which the name phaeodium is given. It consists of a greenish or brownish mass concentrated about the main aperture of the central capsule, but extends around the capsule for a third of its extent. So constant and characteristic is this coloured mass that the term Phaeodaria is frequently used as an alternative to Tripylaria. The constituents of the phaeodium in Aulacantha are various— partly extrinsic, partly intrinsic. To the former class belong diatoms and the débris of other vegetal organisms, small Radiolaria, and Crustacea. Most of these undoubtedly represent food material ; the diatoms, however, may be symbiotic. The characteristic elements of the phaeodium are, however, the phaeodellae, which consist of spherical or ellipsoidal corpuscles which vary from less than 1 » to 20» in diameter. These corpuscles occur singly or in masses. They appear homogeneous, granular, or striated, and vary in colour from a hyaline transparency through yellow-brown, light and dark green, to black. They may be free from inclusions or contain both blackish particles of varying size and refractive granular spheres and rods. Towards reagents they show great refractoriness, and do not give a uric acid reaction (Borgert). About the nature of these phaeodellae, opinion has long been divided. Haeckel maintained that they were symbiotic algae, other zoologists that they were food particles. The recent researches of Borgert on Aulacantha have suggested another explanation. Borgert has pointed out the resemblance of certain granules formed in the endoplasm in the neighbourhood of the astropyle to these phaeodellae, and he regards these corpuscles as excretory products of the endoplasm that pass out through the capsule and accumulate in the surrounding ectoplasm. Recent work on the brilliantly coloured algoid structures in bathybial Challengeridae and Concharidae have shown that probably both assimilation and excretion are carried on in the phaeodium (36). Endoplasm.—The endoplasm is the site of storage and of reproductive changes. It consists of a granular streaming cytoplasm often highly vacuolated, and stratified radially and 120 THE RADIOLARIA concentrically. Imbedded in it are fatty and proteid reserves, pigment, crystalline structures, and one or more nuclei. Oil- globules are generally present in the Spumellaria and Nassellaria, fatty granules in the Phaeodaria. The fat may be colourless or coloured red, yellow, brown, or blue. The pigment is often closely associated with the oil-globules, and occurs in Thalassophysa on the peripheral surface of the globules. The crystalline Portion of a section through Planktonetta atlantica, Borg., one of the Phaeodaria, to show the phaeodium (Ph) filling up the ectoplasm (£z0), x 80. (After Fowler.) Cf. Fig. 29 for whole animal. The black horizontal line is the “diaphragm” or ectocapsular membrane, that is perforated by a single bundle of fibres (Fibr), if not also by the smaller similar structures (C). In the upper ectoplasmic half of the figure the complex phaeodium is seen together with branches (Sp) of the arms. In the lower half the delicate central capsule (C.c.) surrounds thejendoplasm (nd) and nucleus (Nu), and is itself enclosed in a shell (Sh) that forms a float. structures are of two kinds: (a) small whetstone-shaped bodies probably of albuminous nature; and ()) large rhombic structures indestructible at a red heat. The latter, regarded by Brandt as excretory, are in all probability crystals of strontium sulphate (Biitschli). With this exception the contents of the endoplasm may be regarded as reserve material destined partly for the metabolism of the animal itself, but more especially for the provisioning of the spores, into which the endoplasm breaks up. Nucleus.—The nucleus of the Radiolaria is still very im- THE RADIOLARKIA 121 perfectly investigated, and the following statement can only be regarded as a provisional account of its coarser features. The two chief phases of life are signalised by distinctive characters in the nucleoplasm. In the vegetative phase it consists of a single large vesicular structure, or of a few derived from this by mitotic division, or of many equivalent, amitotically produced, small nuclei. In only a few cases are chromidia or other nuclear derivatives as yet known to occur in this phase (Collosphaera, Siphonosphaera, and Aulacantha), and there is no separation of somatic and germinal nucleoplasm. The Radiolaria are, in fact, homokaryota. Neverthe- less, at the advent of the sporulating phase, the nucleus displays new characters. Hither it becomes differentiated and divides into spore nuclei ; or it fragments partly into chromidia and plasma, which recombine to form the spore nuclei, and partly into a residue which perishes with the parental exuviae. In this process we can detect a certain analogy with the extrusion of nucleoplasm during the formation of the spores in the Heliozoa. But since the fate of the Radiolarian spores is unknown, a just comparison of the two cases is at present impossible. The nucleus lies wholly in the endoplasm, and no chromidia or other nuclear products have yet been recognised in the extra- capsulum ; but the axopodia which radiate from the neighbourhood of the nucleus in certain Nassellaria, the similar fibrillae that run from the nucleus outwards to form the flagellum of the Discoidea, are indications of the paths along which the nucleus probably exerts its influence upon the ectoplasm, and vice versa. Further evidence of this perinuclear sphere of influence is found in the apparently porous character of the nuclear membrane (Physematium, Thalasso- lampe, and certain Sphaeroidea) and the radial arrangement of its peripheral plasma. The characters of the nucleus vary according as to whether it is a single or multiple structure. The Collodaria, Sphaeroidea, Nassellaria, and Phaeodaria are generally mononuclear : the Sphaero- zoa and Acantharia, polynuclear forms. In the first group the nucleus is vesicular and differentiated into membrane, sap, chromatin, and achromatin. In the second the nuclei are without a distinct membrane, and, in the vegetative stage, homogeneous ; their origin from the spore or zygote nucleus has been traced in no single instance. One or two special forms of nucleus may be referred to. Among the Phaeodaria the majority possess a nucleus such as that shown in Fig. 15, A, together, in some cases (Aulacantha scolymantha), with chromatin particles scattered through the endoplasm. The Tuscaroridae, however, are peculiar in having (Figs. 13 and 30) an elongate nucleus, with a loop of chromatin enclosed by the nuclear sap. 122 THE RADIOLARIA Among the recently discovered and reinvestigated Spumel- larian families, Thalassothamnidae and Orosphaeridae, a_ totally new type of nucleus has been found (Schréder and Hicker). It consists of a discoid structure (‘1 mm. diam.) enveloped by Ch. a crenate membrane, and is Wy. composed of a thin cortical substance and a central mass” of very distinct nucleoplasm, the cortical and medullary - ge. -Pa, substances being separated , apparently by a membrane (Fig. 14) The central nucleoplasm contains segre- The central capsule and nucleus of Twuscwrora f 1] h seal nationalis. (After Borgert.) As, the astropyle; gated, eeb y chromatise Zn, tne two paapviae; Nw» the nucleus with ¥8 granules imbedded in an achromatic matrix ; the cor- tical layer, on the other hand, is densely chromatised. The most striking feature of this nucleus is perhaps the presence of lenticular bodies at intervals along the junction of its two com- ponent layers, or in one genus (Orosphaera) just outside it. These contain large compact lumps of chromatin imbedded in a less densely staining medium. In addition to this central nucleus, scattered, chromatin-like granules (Fig. 14, s) occur in the endoplasm, and in Orosphaera these peripheral granules are unmistakable nuclei of a simple character. The shape and size of the nucleus often undergo considerable change during growth. It remains vesicular, large, and spherical, S&S W3 Sree ee or oO ——————— ee —~ ————=-_—_. Y 2S SS. a ee SS SS Fia. 13. Fic. 14. Portion of a section through the branched central capsule of Thalasso- thamnus. (After Hicker.) The centre of the capsule with its nucleus (N), endo- plasm, and inclusions are shown. The stratified concretions (s) stain with haematoxylin, and are probably chro- midial structures. In Orosphaera (a genus which, according to Hicker, is - closely allied to Thalassothamnus) these peripheral nucleoplasmiec structures are capable of division. The nucleus (N) shows well the division into crenate membrane, peripheral chromatic layer, and the central, mainly achromatic sub- stance in which groups of staining granules occur. Large lenticular bodies (/) of unknown significance occur also, UK) Ss. CA ¥ SS) 4 C1 (] a @ and more or less chromatised in the Thalassicollidae and Physematiidae ; but in the Thalassophysidae it becomes papillose, elongate, and serpentiform, its plasma not only differentiates into inner and outer substances, but the spherical or thread-like THE RADIOLARIA 123 chromatin accumulates at its periphery (Fig. 21, A, B). In the Sphaeroidea the nucleus becomes tubercular and follows the growth of the central capsule, as this encloses successive shells. In the simpler forms of Nassellaria the vesicular nucleus remains elliptical, but in the Cyrtoidea, in which it lies near the apex of the shell, it sends lobes (Fig. 4, 3) into the adjoining lappets. The multinucleate Radiolaria offer other distinctive characters. In the Sphaerozoa each individual of the colony possesses a gradu- ally increasing number of structureless, singly refracting nuclei, which multiply by direct fission, and have rather the appearance of nuclear fragments than of true nuclei. In the case of Collosphaera and Siphonosphaera, scattered chromidia (not associated as far as is known with reproduction) occur as well. In Acantharia the multiple nuclei have apparently a membrane and nucleoli, the multinucleate condition is constant, and the distinction drawn by Haeckel between such forms and oligo- or mononucleate Acantharia is a mistaken one due to the presence of a parasitic Amoebophrya (Acinetaria), which was mistaken for a nucleus (Part I. p. 423, Fig. 90). More difficult to account for is the careful description by Hertwig of a temporary nuclear condition discovered by him in a species of Acanthometron and of Amphilonche. In the comparatively few nuclei of young specimens, Hertwig found that the membrane became invaginated on its peripheral side, whilst the massive nucleolus showed differentia- tion into two parts. The neck of the infolded membrane became radiately arranged, and its deeper portion creased into circular folds lying one over another. After a time these appearances vanished and the nuclei resumed their simple spherical form. The phenomenon may be one of internal budding. The advent of sporulation is prefaced and accompanied by changes in the nucleus. These changes, however, are but imper- fectly known (p. 139). Vesicular nuclei shrink, their membrane gives way, and the altered chromatin and enclosed nucleoplasm either flows out into the endoplasm or gives rise to a nuclear figure and then disperses (see above, pp. 99-100, for Thalassicolla). From the frag- mented material spore-nuclei arise. By the former method isospore-, by the latter heterospore-, nuclei develop, In the Sphaerozoa, how- ever, the homogeneous scattered nuclei remain undifferentiated during the formation of isospores, and only exhibit a change from a singly to a doubly refractive property ; but previous to the develop- ment of heterospores their nuclei become modified into chromatic and achromatic portions, which are further differentiated in the mega- and microspores. In the Phaeodaria the ellipsoidal nucleus is usually a single large structure, but two or three nuclei may be present. It con- sists (Fig. 14) of a membrane containing a linin network. The chromatin is massed at the centre, and from this point radiating 124 THE RADIOLARIA strands, threads, and lumps run outwards towards the periphery. In addition to these chromatised elements, threads and granules of another substance, the so-called paranuclein of Borgert (18), are present. Nucleoli are absent. The phenomena of nuclear division in this group have been carefully studied by Borgert (17, 18) and Karawiew (16) in Aulacantha scolymantha, but only mitotic division has been fully described. Direct division of the nucleus without elongation is known, but only a preliminary account has as yet been published. The behaviour of the nucleus during sporulation is unknown. Nuclear mitosis in 4Aulacantha exhibits five phases. In the first or spirem stage, the linin threads form a dense coil, along which the chromatin becomes arranged in a moniliform fashion; a few remnants, together with the paranuclein, lie scattered through the nucleoplasm. ‘The coil is in all probability never a continuous thread, and no distinct centrosomes appear at this or any subse- quent phase. The next stage consists of two events. The threads of chromatin become cut up into varying lengths, and split longi- tudinally so as to form rows of chromatin globules on either side of the linin threads. The second event is the condensation of these globules into thick short lengths of double chromosomes. The pairs so formed are unequal in size and different in form, some being spherical, some elongated or rod-like, but the members of a pair are alike. Amongst these the paranuclein granules lie in isolated heaps. The next or third stage is characterised by a second longitudinal splitting of the chromosomes in a plane at right angles to the first. The fission products separate, elongate, and become thinner and twisted, leading up to the fourth stage or second spirem phase, which is so far different from the first in that the chromatin elements are obviously discontinuous, and the nucleus as a whole has now become flattened, discoidal, and bent, in conse- quence of the loss of its membrane, so that it presents, in side view, a somewhat triangular outline, the apex directed towards the astropyle. ‘The large mass of chromosomes is now organised on either side of a median transverse plane passing at right angles to the flattened nucleus. The position of this plane is occupied by a mass of short chromatin elements and débris, between which para- nuclein granules occur. The chromosomes are aggregated on each side of this central mass, which prevents them from being continuous from one side of the nucleus to the other, and are more densely crowded near the centre. The whole flattened structure stretches out until on the aboral side it touches the central capsule. The fifth phase is signalised by the appearance of the equatorial plate. The origin of this structure has not been described, but the chromosomes now arrange themselves in close relation to it, and become heaped up in parallel series, though still maintaining marked THE RADIOLARIA 125 differences of length and thickness. The plate becomes twisted sigmoidally and divides parallel to its surface, the two columns Fia. 15. Mitosis in Aulacantha scolymantha. (After Borgert [18].) A, central capsule and resting: nucleus showing distribution of chromatin. B, second spirem stage showing commencing separation of the chromatin. C, portion of sigmoidally curved nucleus showing the equatorial plate, and the chromosomes definitely arranged about the middle line. D, separation of the: two rows of chromosomes and of the two daughter plates into which the equatorial plate has. divided. HE, central capsule showing the withdrawal of the daughter plates and commencing reconstitution of the nuclei. A, B, and E x 150, C and D x 900. of chromosomes move apart and organise two daughter nuclei (Fig. 15). 126 THE RADIOLARIA These complex mitotic phenomena offer many peculiarities, some of which are discussed by Borgert. The absence of a spindle and of centrosomes, the double splitting, great number and variety of the chromosomes, the peculiar twisting of the nucleus and equatorial plate, and the two spirem stages render this form of karyokinesis unique ; and in spite of the labour which has been bestowed upon its analysis, several points, such as the origin and fate of the equa- torial membrane and the formation of the daughter nuclei, are still obscure. Yellow Cells.—Zooxanthellae occur commonly in the ectoplasm of Spumellaria and Nassellaria ; in the endoplasm of Acantharia ; and Fic. 16. land 2, two specimens of Collozowm inerme, showing zooxanthellae (Z) in the ectoplasm, x 100. 3, 4, and 5 are magnified views of a single xanthella, showing its escape as a biflagellated organism from the cyst which it forms during the palmella state (x 330). K, the nucleus; chr, the two chromatophores ; the inclusions are hollow, amyloid grains. (After Brandt.) are absent from the Phaeodaria. Their occurrence is facultative and not absolutely constant. They are very abundant in orders with a well-developed calymma such as the Collodaria (both mono- zoic and polyzoic), less so in the Sphaerellaria, and in Physematiidae with no extracapsular vacuoles, and are absent in the Discoidea. Similarly, zooxanthellae increase in number with the increase of size of the animal or coenobium in which they occur. Young colonies of Collozoum up to 50 or 100 members contain few or no zooxanthellae, older ones become impregnated with them. The zooxanthellae of the Spumellaria are similar in structure and behaviour to those of Thalassicolla (pp. 97-8). They are usually spherical organisms with a single apparently homogeneous nucleus, capable of assimilating carbon and of forming sheaths of a singly THE RADIOLARIA 127 refractive amyloid substance around a clear centre. In the Collodaria they vary from ‘015 to (025 mm. in diameter ; in the Sphaerellaria from ‘005 to ‘(01 mm. In the Nassellaria the zooxanthellae are very small in some Cyrtoidea (Hucecryphalus) ; very large in others (Eucyrtidium, Dictyopodium). A cellulose wall is present and en- closes cytoplasm which contains two chromatophores impregnated by chlorophyll and diatomin. In addition to the scattered hollow vesicular, singly refractive structures that react to iodine by a violet or bluish-violet tint, other doubly refractory granules occur, and these are unaffected by iodine. After the death of the ecto- plasm in which these zooxanthellae live, they pass into a palmella stage and issue as biflagellated organisms upon a free stage. The structure and life-history of these zooxanthellae prove that they are organisms living in association with Radiolaria, but it is not possible to assign them to their true systematic position. Most authors, following Biitschli, have placed them in the Crypto- monadinae, a small heterogeneous group of simple algae; but, as Schaudinn has pointed out in his work on the zooxanthellae of Trichosphaerium (42), it is also possible that these organisms have quite other affinities. Brandt (10a) and Klebs (46) have drawn attention to the similarity between the flagellated stage of the xanthellae and the Peridinian Exwviaella marina. Further investiga- tion of the behaviour of these yellow cells is necessary before their position can be accurately defined. Yellow Cells of Acantharia.—The xanthellae of the Acantharia differ in many ways from those of other Radiolaria. They are mainly intracapsular, and always naked cells. In some families they assume a spherical form, in others an irregular amoeboid shape. These cells pass by easy transitions to mere heaps of pigment granules. When numerous they vary in size from ‘006 to ‘008 mm. When few they attain a much larger size, ‘015 to ‘03 mm. The latter, which are found in Acanthoniidae, Lithopteridae, and Amphilonchidae, are probably the largest zooxanthellae known. In Acanthonia tetracopa and other members of the same family, besides’ the usual intracapsular mass of zooxanthellae, a few occur now and then in the extracapsulum. In Dorataspis and Actinomma large amoeboid zooxanthellae occur regularly in this position. These structures are almost constant in Acantharia, but they are absent in young specimens and in the few species taken in deep water. The observations of Brandt (10a) on the finer structure of the Acantharian zooxanthellae suggest that they have acquired a much closer association with these Radiolaria than have those of Spumellaria with their host, and that the older view of their nature was nearer to the true significance of the association than the modern one that regards the zooxanthellae as merely immigrant algae. Haeckel and Hertwig regarded them as pigment cells formed by the segregation 128 THE RADIOLARIA of the scattered granules and vesicles about so many nucleated centres in the endoplasm, and therefore as integral parts of the Radiolarian, acting the part of storing reserve material. Brandt has shown that their structure, though not suggesting this view of their origin, serves to explain the connection between the pigment granules, pigmented granular heaps, and definite yellow cells. Starting from. the last, with its single nucleus, plates of diatomin, numerous amyloid vesicles and refractive granules, Brandt finds other xanthellae with multiple minute nuclei, and by fragmentation of these yellow cells he accounts for the presence of the isolated yellow granules, each of which, he affirms, is a living corpuscle and possesses a very small nucleus (10a, p. 237). This degeneration of the zooxanthellar nucleus into a heap of chromatin granules, associated with the breaking up of the Fic. 17. A-C, yellow cells (zooxanthellae) of Acantharia. (After Brandt.) A, large amoeboid cell from Acanthonia tetracopa. B, C, spindle-shaped zooxanthellae (A. tetracopa). OD, single xan- thella of Thalassophysa sanguinolenta, to show its ceil-wall (C.w), hollow, singly refractive inclusions that stain bluish violet with iodine. G, doubly refractive granules unaffected by iodine. x 1000. cell, is probably not to be explained through digestion of the yellow cells by the Acantharian, but as a consequence of the intimate association between the two structures. Unlike the zooxanthellae of the Spumellaria, which live, divide, and sporulate after the death and dissemination of their host, those of the Acantharia lose their power of independent existence, and when the endoplasm in which they occur becomes transformed into isospores or heterospores they too pass into these spores in the form of granules and starch grains. Thus the flagellated heterospores of Xiphacantha alata (Fig. 26, A) contain a mass of yellow granules, besides an amyloid body (staining blue with iodine), which is constantly present in the iso- and heterospores of this species. It is therefore possible that the yellow cells of Acantharia pass from mother to offspring, and it is certain that amyloid deposits are so transmitted. The zooxanthellae of Acantharia, therefore, once they have entered the Radiolarian, THE RADIOLARIA 129 never leave it. They become assimilating granules, apparently incapable of independent life, and are transmitted from parent to offspring. In the former conclusion we have a remarkable parallel to the history of the green cells (zoochlorellae) in Convoluta roscoffensis (Keeble and Gamble [41}). The nature of these interesting zooxanthellae is not satisfactorily settled, but the scanty evidence points to affinities quite distinct from those of the other Radiolaria. In the absence of a knowledge of the life-history, Brandt’s view is as likely as any other, but it is by no means certain that all the Acantharian zooxanthellae are of similar parentage. This view is that the zooxanthellae of Acanthoniidae and Dorataspidae are isolated spindles of Labyrinthula vitellina or of some allied species, and Brandt (10a, p. 239) points out the agreement between the two structures in their shape, size, colouring, and nuclei. The association between Radiolaria and the zooxanthellae is usually regarded as a symbiosis, 7.¢. one of mutual advantage. It is, however, clear from the foregoing description that no single formula will cover the important facts—(1) that we have degrees of intimacy that have grown up between the two organisms ; and (2) that the last term in the series of association is one to which symbiosis in any but the widest sense of that term is inapplicable. The origin of the association is probably to be traced to the hunger for nitrogen on the part of the zooxanthellae; to the minimal quantity of inorganic nitrogenous food-stuffs in the warmer seas (Johnstone [45]); and to the convergent adaptation of Radiolaria and zooxanthellae to life at or near the surface of the ocean. This pelagic and insolated station is attained by the Radiolaria through the evolution of calymmal structures in which nitrogen is in all probability abundantly present. These swarms of inert mucilaginous Radiolarian capsules and colonies are therefore in every way suitable media for the nutrition of the zooxanthellae. Attracted in all probability chemotactically by the nitrogenous stores in the mucilage, the zooxanthellae enter the ectoplasm and then divide and assimilate. Protected by their cellulose envelope, they can at first resist the digestive enzymes of their host; ultimately, however, their nucleus becomes degenerate, and with this change the protective wall, whose formation it governs, becomes weakened. In this way some of the daughter-cells of the primary zooxanthellae become food for their host (Famintzin). The Radiolarian, which in its early stages fed on Peridinians, Infusoria, and small Crustacea, ceases to ingest solid food and relies upon the reserves it has accumulated or upon the secondary xanthellae for its supplies. Meanwhile, its nitrogenous metabolism, and possibly its intramolecular respiration, is maintained by the xanthellae, which are removing the waste nitrogenous substances. In confirma- 9 130 THE RADIOLARIA tion of this statement reference may be made to the Phaeodaria. This group of Radiolaria possesses no zooxanthellae, and might therefore be expected to show some accumulation of excretory granules. ‘This appears to be the case, for the complex phaeodium is made up of refractory, insoluble vesicles which are generally held to be excretory substances. The association of diatoms with Radiolaria has probably a similar significance. Finally, when the endoplasm sporulates the dying ectoplasm serves as a medium in which the zooxanthellae rapidly divide and issue as naked biflagellated spores upon a new, free existence. In the case of the Acantharia, which are also mainly epiplanktonic or surface organisms, the zooxanthellae are naked cells, almost exclusively confined to the central portion of the Radiolarian. Whether they develop from antecedent zooxanthellae that occur in the spores of Acantharia or infect it from sea-water, or whether both modes of origin obtain, is at present unknown. The apparent absence of xanthellae from young Acantharia makes the first sugges- tion unlikely. Within the central capsule they divide, multiply, and assimilate. Certain of them fragment into particles, the process being initiated by nuclear fragmentation, so that the zooxanthellae are no longer cells but mere chromatised, pigmented corpuscles, associated with free granules of starch or amyloid substances. There is no evidence to show whether in this or in the earlier coherent stage the xanthellae are digested by the Acantharian. They become in the last event mere assimilative corpuscles, and when the endoplasm sporulates the whole of the zooxanthellae, with their associated starch, pass into the bodies of the flagellated spores, and are probably used up as food by the developing zygote. Throughout this series we see that, in opposi- tion to the idea of mutual benefit, the animal is the predominant partner. ‘The association is one beginning with myxophytism and leading to a case of parasitism, in which the zooxanthellae are the host and the Radiolarian the parasite. Skeleton.—The skeleton of the Radiolaria has developed in each of the great sub-classes into a complexity of form and variety of detail that are found in no other group of animals, So characteristic are the skeletal products that it is usually possible from them alone to recognise broadly the systematic position of the organism that produced them. So complex and diverse a tracery seems utterly beyond the needs of simple Protozoa living under apparently similar conditions of pelagic life; and though attempts have been made to explain this manifold skeletal development in terms of cytoplasmic structure, its variety still evades a biological treatment. Recent investigation has, however, done something to reduce this variety to a few plans, and to attach a biological meaning to some of its elaborations. These results justify the hope that, as we come to THE RADIOLARIA 131 regard the skeleton as a response to the varying media, stresses, and strains that fall upon the cytoplasm from within and from without, that then its utilitarian character will be more completely recognised, and its variety found to be explicable in terms of com- position, mode of deposition, and the need of response to widely varying combinations of stimuli that occur in the apparently mono- tonous sea. ‘Two very different substances compose the greater part, and probably the whole, of these skeletal structures. In the Spumellaria and Nassellaria pure silica is present ; in the Phaeodaria the silex is mixed with organic substance ; but in the Acantharia a substance is present which, from the time when it was first described by Johannes Miiller to the present, has given rise to differences of interpretation. Miiller, relying on the indestructible nature of the Acantharian skeleton when heated, regarded it as siliceous. Haeckel found that it was apparently destroyed by heat, and regarded it in the main as an organic horny substance which he called acanthin. Schewiakoff (33) tested its properties and attempted a quantitative analysis, the result of which went to show that the so-called acanthin was a complex silicate. Quite recently Biitschli (39) has reinvestigated the skeleton of Antarctic and of some Mediterranean Acantharia, and has proved that in these cases it is composed of strontium sulphate. The diverse forms of Radiolarian skeletons are largely founded upon developments of scattered aciculate and tetrahedral spicules. Dreyer has indeed attempted to trace the evolution of the skeleton (1) in the Acantharia to an axopodial type derived from the hardening of the axis that runs down the peculiar radiating pseudopodia of this sub-class ; and (2) in other Radiolaria to the modifications of a tetrad spicule, which in turn he traces to the deposition of silica at the intersecting planes of adjacent cyto- plasmic vacuoles or alveoles; but the absence of a knowledge of the development of the skeleton rendered this attempt suggestive rather than convincing, and there are many forms of skeleton which it is difficult to assign to any conceivable modification of the tetrahedral type. In the present state of our knowledge it must be admitted that the vacuolated cytoplasm has the power of depositing its silica in the form of perforate or imperforate shells, plates, and processes, so that in addition to the spicules there is often a great development of siliceous matter, the form of which cannot be referred to the alveolar structure of protoplasm. In form as in composition the skeleton of the Acantharia is sharply marked off from that of other Radiolaria. With few exceptions, it consists of twenty rods united in various ways : (1) by apposition and also by adcentral processes ; (2) by fusion of all or of opposite pairs, at the centre of the endoplasm. These radii are disposed so as to emerge from the spherical cytoplasm along five 132 THE RADIOLARIA circles, which may be compared to the equatorial, the two circum- polar, and the two tropical circles of the globe (Miiller’s law). In a few cases two radii mark the vertical axis, and the other eighteen are disposed in three circles—an equatorial one, and the other two respectively 45° above and below it (Brandt’s law) ; whilst in the apparently primitive Astrolophidae the spines vary in number and Fia. 18. Acanthonia tetracopa in its two extreme phases of expansion and contraction, one half of the animal being drawn in each case. The relation of the myonemes to the ectoplasm, and their insertion into sheaths around the radial spines, is also seen (cf. Fig. 11). The full number (20) of spines is not indicated. (After Schewiakoff.) x 170. possess no regular arrangement beyond their radial disposition. This loose order is repeated in the early development of the Acan- thoniidae. The young of this family possess ten loose rods arranged crosswise, which subsequently become divided at the centre of the capsule into the typical twenty radii. In the Acanthochias- midae the distal portion of each radius gives off tangential processes which unite with those of adjoining spines and so form a perforated THE RADIOLARIA 133 shell. By repetition of the process farther along the radii a second and succeeding concentric shell may arise. In the most modified case (Sphaerocapsidae) the lattice alone is present, but the place of the radii is shown by twenty large pores distributed according to Miiller’s law. In the Spumellaria the skeleton is either absent, spicular, or shelly. Both spicules and perforated shells are often present simultaneously, and have evidently developed independently in two of the main subdivisions—Sphaerozoa and Sphaerellaria. But whilst in the former the shell is single, in the latter it often becomes multiple, interconnected by radial bars, and flowers out into a wealth of appendicular growths that characterise this vast group, which numbers two-fifths of the known Radiolaria, The Sphaeroidea retain the homaxonial form; the Discoidea have only the first or first and second chambers spherical, and farther outwards become flattened and often cruciform, the arms of the cross being frequently divided into a large number of chambers, into all of which the endoplasm and its associated pigmented oil-globules may pass. Other modifications are mentioned in the conspectus (pp. 144-145). In the Nassellaria, the Radiolarian skeleton develops into its richest expression of geometric form. Its simplest types consist of a single or multiple ring and of a tripod or tetrad (see Fig. 5), and from these a helmet-shaped perforated shell has arisen, apparently by lateral extensions of the simpler plan. Such a cephalis may be simple or divided both sagittally and transversely by one or more constrictions, and in exceptional cases a spherical shell may be developed. The most interesting feature of this group is that the whole of its variety can be traced fairly confidently to the modifi- cations of a single element which Biitschli (8) believes to be a ring and Dreyer (15) a tetrad spicule. The skeleton of the Phaeodaria has followed another line of evolution. It consists essentially of minute aciculate spicules imbedded in a gelatinous matrix. Between these a jelly-like substance is secreted ; the inner layer of this matrix becomes silici- fied to form a tube, the cavity of which is often subdivided by one or more septa; or the intermediate jelly may also become silicified as a porous plate or shell of porcellanous texture. Commencing with the Phaeocystina, in which the skeleton is absent or composed merely of isolated radial and tangential spicules, the formation of a lattice-shell has come about in several ways. The simplest mode is that seen in the Aulosphaeridae, in which the tangential spicules unite to form an open peripheral network. To this a second shell may be added by the formation of a reticulum immediately outside the central capsule (Cannosphaeridae). If the outer shell is absent, a condition found in the Castanellidae is obtained. In these Phaeodaria the single shell is composed of two conjoined membranes 134 THE RADIOLARIA imbedded in a porcellanous impregnation throughout which minute aciculate spicules occur. It is provided with an oral opening on the end of a projecting and often spiny peristome. Again, this inner shell may assume a bivalvular form (Fig. 32), and then carries a number of complex appendages. Some of these are branching hollow species, terminating in anchor-like expansions ; others constitute the “oalea” and “rhizocanna” (see Fig. 32, p. 151). Biological Significance of the Skeleton—The results of recent investigation point to the conclusion that the chief skeletal function is a hydrostatic one and is effected by stretching or folding the superficial ectoplasm. The older conception of the skeleton as projecting freely beyond the cytoplasm has been shown to be a mistaken one in many instances, and it is probable that the skeleton is during life covered by the outermost delicate plasmic layer in all Radiolaria. Between the characters of this layer and the development of the supporting rods a definite relation holds for certain forms. A few widely varying Radiolaria are dimorphic, a small pelagic variety and a larger abyssal form being readily and apparently rightly distinguishable (Aulacantha scolymantha, Auloscena and Sagosphaera-species). In these cases the surface-form possesses — a delicate ectoplasmic layer, and the supporting rods are simpler and shorter, whereas in the bathybial variety the outermost cytoplasm is dense, more voluminous, and usually more stiffly sup- ported by verticillate skeletal projections. The graceful and elaborate skeletal appendages of other Phaeodaria are probably to be explained not as a means of catching food, but as a support for the ectoplasm ; and the whole plan and construction of the tubular skeleton in these forms is no doubt related intimately to the pressures that fall upon this limiting layer. In connection with this sustentative function of the Phaeodarian skeleton, the mode of formation of its tubular systems offers some features of special interest. The most general mode is that indi- cated at the close of the last section (p. 133), and in this method minute needle-like spicules form the centre around which tubular developments of silica take place. But in addition to this intrinsic centre, many Phaeodaria have adopted extrinsic objects, and around these as catalysators, the tubular silica is deposited. Like other Radiolaria, but to a greater extent, the Phaeodaria ingest quantities of foreign bodies, with which their phaeodium is distended. Amongst these ingesta, diatoms and Radiolarian skeletons are abundant. From Phaeodaria, in which such gatherings are casual, we can trace a series leading to forms in which diatom-selection becomes a regular habit, associated directly with the formation of a radial skeleton. Thus Aulographis pandora and Auloceros wrborescens from the Atlantic and Indian Oceans contain in their phaeodia frustules of /hizosolenia, and spicules of many species of Aulacanthids picked up apparently in THE RADIOLARIA 135 a casual manner, and probably serving to increase the extent of exposed surface. Cannosphaera from Antarctic seas possesses a hollow skeleton the tubes of which are almost filled with masses of the diatom Corethron; and finally, in Aulokleptes (Fig 19) and Aulodendron the diatoms are planted radially in the ectoplasm, surrounded by a mucilage, and finally incorporated into the walls of a hollow radial tube, the lamellae of which are laid down from within outwards, and the top of which is moulded into the form severally characteristic of the species (Immer- mann, Hiicker). The biological significance of the varieties of Nassellarian spicule and of the scattered Spumellarian spicules and lattice-shells is at present quite obscure, but the skeleton of the Acantharia offers perhaps the clearest case of func- tional significance to be found in the whole group (Dreyer, Brandt, Popowsky). The twenty radial spokes of the Acanthometrea serve Fia. 19. as sO many tent-poles for the in- Spicule from Aulokleptes flosculus formed sertion of the myonemes (Figs. 11 (Aftep Tntienrnane) eo emai lat and 18) that hoist the calymmal cones. This action, combined with absorption of water into the vacuoles, causes a swelling of the cytoplasm and brings the animal towards the surface; whereas relaxation of the myonemes and contraction of the calymma depresses it beyond the reach of waye-action. The skeleton of this subdivision is, however, related to hydrostatic ends in another way. The definite arrangement of the twenty spines according to what is known as Miiller’s law (p. 132) has recently been correlated with flotation and dispersal. Brandt has shown that the distribution of the radii in five alternate and superposed circles, each of four spicules, is such as to expose them freely and without overlapping to the viscosity and resistance of the water. The absence of vertical or axial spines is also intel- ligible, since they would increase the weight of the body without giving additional buoyancy. Moreover, the shape as well as the arrangement of the spines assist the Acantharia in their flotation and dispersal. Like all other Radiolaria, these are dependent on currents and drift for their dissemination. In order to utilise this horizontal force, the radial spokes are frequently provided with four flanges or blades, which serve the double purpose of encountering 136 THE RADIOLARIA sustentative and propulsive forces. When these blades are wanting and the spines are merely flattened, they are set in each of the three circles, so as to turn the flat edge somewhat differently to the water, the equatorial ones lying flat on the water, the tropical ones turned half over, and the polar spines set on edge. By this means the amount of resistance to the water in every direction is increased. The exceptionally wide distribution of the Acanthometrida is some ~ confirmation of these deductions. Fission—Reproduction.—The phenomena of multiplication and of reproduction are still imperfectly known. Binary or multiple fission occurs in some Spumellaria, Acanthometrida, and Phaeodaria. Gemmation is a rarer mode. It produces the extracapsular bodies of the Sphaerozoidae, and is found in one species of the Acantharia and of the Phaeodaria respectively. The development of zoospores is a general phenomenon, but has been followed in detail only in a— few cases. Plastogamy is unknown. The mode of increase by fission is probably restricted to those Radiolaria which have no spicules or a lax and osculate skeleton. Binary fission occurs in the Thalassicollidae, some Acanthometridae, and in two families of Phaeodaria. Division both of the Sphaero- zoid colony and of its component individuals takes place at intervals. Multiple fission occurs in the Thalassophysidae. The process is usually initiated by changes-in the endoplasm and nucleus, and a_ long interval may follow before any corresponding alterations occur in the ectoplasm (Phaeodaria). In the Acanthometrida (Acanthoniidae) binary, quatenary, and multiple fission are said to occur (Popowsky). The former process is illustrated in Fig. 20. The skeletal rods separate at their central ends into two bundles, the nuclei segregate into two groups, the central capsule divides, and ultimately fission takes place. The fission- products are, however, asymmetrical, and Fig. 20 shows how the new radii are developed and how the rods are swung into position, probably by contraction of the myonemes inserted into them, until the whole arrangement is brought into conformity with Miiller’s law. Fission in the Phaeodaria is carried out in several ways. Aulacantha scolymantha is the best-known example of the direct process. In this Radiolarian the large single nucleus divides either by mitosis or amitotically ; the endoplasm segregates round the daughter nuclei; the central capsule, after disappearing for a time, re-forms about the two masses. Lastly, the phaeodial complex, the calymma and spicular skeleton are subdivided each into two groups, and the whole organism divides into two. In the Phaeodaria, which possess a shell, one or more modifications of the process are found. The helmet-shaped Challengeridae, for example, undergo fission within the shell. One half of the organism now escapes THE RADIOLARIA 137 through the oral aperture and develops into a new individual (Borgert [21a], p. 100). The most remarkable case of multiple fission occurs in the Thalassophysidae, and constitutes the only known means of increase | Fia. 20. Illustrating fission in the Acanthometrida. (After Popowsky.) A, Acanthometron bifidum about to divide. The spicules are arranged in two bundles. The central capsule has dis- appeared. The ectoplasm is a mere hyaline border round the granular endoplasm, x 150. B, fission of Amphilonche atlantica. My, the myonemes, x150. CC, regeneration of the same ; formation of a directive large spicule, x150. D, spicules reassuming their characteristic arrangement, x 150. in this family. Fig. 21 illustrates the process, which has been investigated by Brandt (25). The central capsule and nucleus become irregular-branching, vermicular, or radiating structures. The oil-globules and their associated pigment granules become dis- seminated through the endoplasm. ‘Then the nucleoplasm breaks up into a vast number of minute homogeneous corpuscles, followed 138 THE RADIOLARIA by rapid division of the capsule and endoplasm. The ectoplasm fragments and the products are disseminated through the water. Each minute product consists of several nuclei lying in a pigmented, oily fragment of endoplasm and supported by a portion of the original ectoplasm. The further history of these bodies is unfortu- nately not known. K~ \ \ _ > Sib gid >. i ’ \ Fia. 21: Multiple fission in Thalassophysidae. (After Brandt.) A, central capsule and nucleus of Th. spiculosa, x 40. B, section of the nucleus to show the two zones of nucleoplasm and the vermicular nucleoli in the outer layer, x 66. C, Th. pelagica about to divide ; the nucleus has undergone fragmentation. D, multiple fission of the central capsule of Th. pelagica. E, enlarged view of a portion of the same, x 200. F, stained portion of capsule of the same to show nuclei before fragmentation of the capsule. G, division of central capsule of Th. sanguino- lenta, x 7. C.c, central capsule; N, nucleus of vegetative individual; Nj, nucleus of frag- menting individual ; On, In, outer and inner zones of endoplasm. The separation of a portion of the Radiolarian organism as @ bud is a rare phenomenon, of which the “extracapsular bodies” of the Sphaerozoidae offer the best example. These structures occur in small colonies of Collozowm inerme, C. radiosum, C. fulvum, and of Sphaerozoum neapolitanum. They consist of a lobate, highly refrae- tive, cytoplasmic mass, containing a group of modified nuclei ranged about a grape-shaped mass of fat, and are loosely attached to the colonial jelly (Fig. 22). These extracapsular bodies are budded off from the endoplasm of certain members of the colony in which they occur, and are at first uninuclear. According to Brandt's THE RADIOLARIA 139 account (10) these bodies have a twofold significance. Hither they become additional members of the parental colony and develop central capsules, or they become megaspores and the small parental endoplasm develops microspores. In his later work Brandt lays additional stress on the latter fate. He has not only seen the bean- shaped active megaspores formed by the extracapsular bodies, but (26, p. 264) also the mass of microspores formed by the small capsules which had budded off these bodies: a proterogynous arrangement. It should be added that Brandt affirms very strongly the juvenile nature of these small budding colonies ; whilst F'amintzin, Fia. 22. Collozowm sp. Portion of a colony showing extracapsular bodies (Z.C). x 100. (After Brandt.) working in the same locality, asserts that their small size is due to fission of full-grown coenobia (13). Spore - Formation.—F lagellated spores occur in the four main divisions of the Radiolaria, but their exact nature is only known in some Collodaria and some Acantharia, and it is in the former order that their formation has been traced. The process is described for Thalassicolla on pp. 99-102. Isospores. —'The development of isospores in the Sphaerozoa takes place in colonies distinct from those that produce heterospores. After a vegetative life of several months these colonies exhibit characteristic changes (Fig. 25). The nuclei become ranged in a single or double row just beneath the capsular membrane. Without becoming obviously differentiated, these lumps of chromatin divide directly and acquire a doubly refractive character. Hundreds of 140 THE RADIOLARIA minute crystals arise in the endoplasm, a few larger ones also in certain Collosphaeridae. The single oil-globule of each capsule becomes very rapidly subdivided into as many minute vesicles as there are nuclei, and in association with this process a blue pigment develops Fic. 23. Collosphaera huxleyi. Optical sections of different growth-stages to illustrate (A, B) dimor- phism (S;, Sy) in early and later stages, and (C, D) the formation ofisospores. A, youngactively dividing colony (the young reproductive phase of Brandt, comparable with the.formation of extracapsular bodies in Sphaerozoidae). Many individuals are naked central capsules with one or more nuclei; others have a shell (S;) and are larger and already provided with zooxanthellae (z). B, later vegetative phase. The naked capsules have now secreted a —_ shell (Sg), and a marked dimorphism has resulted. C, part of a full-grown colony about sporulate. The formation of isospores is indicated by the grouping of the nuclei. D, later stage in isospore-formation showing the crystals aggregated about the oil-globule. x 75. (After Brandt.) in Myxosphaera coerulea and Collosphaera huxleyi. Numerous vacuoles arise in the centre of the capsule, each with a central granule, until a number equivalent to that of the nuclei has been formed. Mean- time these nuclei, which have become very numerous, are evenly THE RADIOLARIA I4I disseminated through the endoplasm forming the centres about each of which a crystal, an oil-vesicle, a vacuole, and granule are Fig. 24. Portion of a colony of Sphaerozowm neapolitanum about to form isospores. The spicules and “vellow cells” are omitted. The central capsule has disappeared, and only a thin peripheral ectoplasmic layer is present. Minute crystals are scattered through the endoplasm, and two oil-globules (0) are shown. x 300. (After Brandt.) clustered. The whole endoplasm is now transformed into a mass of biflagellated spores. The central capsule suddenly disappears, and the ectoplasm, which in the interval has undergone contraction B. Hic. 25. A, formation of isospores in Collozowm inerme. Two stages are shown on opposite sides of a central capsule. On the left side the nuclei and crystals are aggregated peripherally, but the central oil-globule is intact. On the right the nuclei are smaller and more numerous and the oil-globule is breaking down. B, formation of heterospores in the same shown by quadrants. a, early stage ; several grouped, modified nuclei and fat-granules ; between the groups are undif- ferentiated nuclei and endoplasm; b, c, and d are later stages. and degeneration, breaks to pieces. The colony descends and the isospores swarm out, leaving (in the Collosphaeridae) the large crystals and the greater part of the-pigment behind. Each is a 142 THE RADIOLARIA conical structure (‘012 mm. long). From its pointed end spring the two cilia, one of which is usually held in a somewhat horizontal position, the other curving backwards and downwards. Near this end lies the nucleus, which has acquired, according to Brandt (10, p. 163), a certain differentiation. The broader end is filled with the crystal and granules (Fig. 26, E). Heterospores—The formation of megaspores and microspores may proceed from the same (Sphaerozoidae) or separate colonies” Fia. 26. Isospores and heterospores of Radiolaria. A, heterospores of Xiphacantha alata (Acantharia). B, isospores of the same. C and D, microspore and megaspore of Collozoum inerme. E, isospore of the same showing crystal and inclusions. F and G, megaspores of Sphaerozoum sp. H, microspores ofthe same. (After Brandt.) (Collosphaeridae). The process differs from the development of isospores in the presence of segregated nuclei, the differentiation in the nuclei of achromatic substance, and the dimorphism of the mega- and micro-nuclei. In the Collosphaeridae the full-grown vegetative colony shows the first traces of heterospore-formation by the segregation of its homogeneous nuclei into groups of 2, 4, or 8. This arrangement is temporary, and very soon the nuclei are found arranged in several layers, each nucleus being now clearly composed of a highly refractive and achromatic ground-sub- stance, in which are imbedded thread-like masses of chromatin. THE RADIOLARIA 143 According to the colony under consideration so will these nuclei belong either to the microspore or megaspore. In the former the chromatin is disposed in stout granules and thick strands, in the latter in much smaller quantity. In other respects the colony behaves precisely as in the formation of isospores. In the Sphaerozoidae the formation of heterospores takes place both in small, apparently young, colonies that bear extracapsular bodies and also from full-grown vegetative colonies. In both cases many of the nuclei become segregated and differentiated, the endo- plasm in which they lie acquires distinctive characters, and the groups so formed are separated by undifferentiated plasma and nuclei (Fig. 25, B). ‘The oil-globule becomes subdivided into a grape- like mass, which ultimately splits up into minute granules, and these are collected around the specialised nuclei. In the case of colonies bearing extracapsular bodies the whole of this bud becomes transformed into megaspores, the contents of the central capsule becoming microspores. In older colonies the endoplasm is con- verted into a vast number of portions, in each of which the differ- entiated nuclei are aggregated. ‘These nuclei are, however, not all of one kind. Lach collection is either meganucleate or micro- nucleate, and accordingly stains feebly or strongly. The contents of the capsule now becomes resolved into biflagellated megaspores and microspores, the ectoplasm degenerates and collapses, the central capsule deliquesces, and the spores become disseminated. Little is as yet known as to the formation of isospores and heterospores in other Radiolaria. In Acanthochiasma rubescens (Acantharia) Brandt records the early development of two kinds of bodies—one with crystalloid inclusions, the other with lobulated masses of fat. The same observer has described the active spores of Xiphacantha alata and Acanthometra sicula. 'Two kinds of spores occur in these Acantharia (Fig. 26, A, B). Both are minute (004 mm. long), and provided with three cilia, which spring from the two poles of the spheroidal or pear-shaped body, but they differ in that the spores of any one individual either contain a minute crystal and few granules or many granules but no crystal. Both are provided with a starch-grain (see pp. 128), and traces of the yellow cells of the parent occur in the granular variety. It seems highly probable, therefore, that crystal-bearing isospores and granular heterospores occur in this sub-class as in the Spumellaria; but although the results of more recent expeditions have extended very largely the number of Acantharia in which the early development of spores has been shown to occur, the free spores have not been again noticed; nor do we possess any exact observations on the flagellated bodies that have occasionally been seen in Nassellaria and Phaeodaria. 144 THE RADIOLARIA CLASSIFICATION. CLASS RADIOLARIA. Sus-Cuass I. PERIPYLARIA (Spumellaria). Central capsule homaxonic, uniformly perforated by numerous similar and extremely small pores. Skeleton siliceous. Extra-capsulum volum- inous (except in Physematiidae), OrvDER 1. Collodaria. Large monozoic forms not forming a true coenobium. Skeleton absent or spicular. Faminy 1. PHyseMatlpAr. Large vacuoles confined to the endoplasm. No stratified concretions in the latter. No pigment. Few “yellow cells.” Nucleus spherical, with smooth membrane and a few rounded nucleoli. Selected forms :—Physematiwm miillert, H. ; Thalassolampe margarodes, H., Mediterranean and Canary Islands; Lampoxanthium murrayanum, Fowl., Faroe Channel. The genus Actissa of Haeckel is an early stage of growth of some species of this family. : Famity 2. THALASSOPHYSIDAE. Large vacuoles extracapsular. Structure similar to that of the Thalassicollidae, but nuclear membrane usually tubercular or papillary. Reproduction by rapid and peculiar fragmentation (Fig. 21). Spores unknown. Selected forms :—Thalas- siosolen atlanticus, Wolf. (28); Thalassophysa pelagica, H. (Fig. 1), Faroe Channel; T. sanguinolenta, H.; T. papillosa, H., Mediterranean and Canary Islands (often deformed by ingested Coccolithophoridae). For further account of this family see Brandt (25). Famity 3, THALASSICOLLIDAE. Nuclear membrame smooth and spherical. Stratified concretions present in the endoplasm. Multiplica- tion by binary fission, by isospores, and by heterospores (see Fig. 2 ; Brandt [25, 25a, and 26]). Selected forms :—Thalassicolla nucleata, Hux., Valencia Harbour, Faroe Channel, and cosmopolitan; J. spwmida, H., Canary Islands; 7. pellucida, H., cosmopolitan, Famity 4. THALASSOTHAMNIDAE, Hacker (37). Skeleton in the form of a large single radiate spiculum or of a double spiculum. Central capsule sometimes spherical, characteristically lobed or branched. Nucleus complex. Nuclear membrane crenate (Fig. 14). Endoplasm with stratified inclusions. Selected forms :—Thalassothamnus ramosus, Hiick., Antarctic ; Cytocladus spinosus, Schréder (Fig. 10), Japan Seas (38). FAMILY 5. OROSPHAERIDAE. Protoplasm organised as in the preceding family. Skeleton a perforated shell with branched and thorny spines. Orosphaera, H., deep water of mid-Atlantic. This family has been re- moved by Hicker (37) from the Phaeodaria, with which group Haeckel associated it ; but if the presence of a phaeodium, astropyle, and parapyles is confirmed, its systematic position will have to be revised. ! ‘he number of genera and species in this class is so large that only a selection can be referred to here. North Atlantic forms have been chietly selected. THE RADIOLARIA 145 OrprER 2. Sphaerozoa. Colonial forms. Faminy 1. SpHarrozorpAn. Both mega- and microspores developed in the same individual. A lattice-shell absent. Selected forms :— Collozoum inerme, Norway (Figs. 3, s, and 25); C. pelagicwm, Shetlands ; Sphaerozowm ovodimare, Faroe Channel. FAMILY 2. COLLOSPHAERIDAE. Mega- and microspores in separate individuals. Skeleton, when present, takes the form of a lattice-shell with or without associated spicules. Selected forms :—Collosphaera hualeyt, Mediterranean (Fig. 23) ; Choenicosphaera murrayana, Shetlands. This order is treated fully by Brandt in his Monograph (10) and (22). OrpeER 3. Sphaerellaria. Sus-Orper 1. SpHAEROIDEA. Central capsule and shell (or shells) spherical. Selected forms :—Heaalonche philosophica, H., Faroe Channel ; Hexacontium enthacanthium, Jorg.; H. pachydermum, Jorg., North Sea ; Hexadoras borealis, Clev., North Sea; Hchinomma leptodermum, Jorg., Norway and Sweden ; Rhizoplegma boreale, Clev., Norway. Susp-OrpgerR 2. PrunorpEA. Central capsule and shell elliptical or cylindrical ; often with transverse constrictions. Selected form :—Pruno- carpus datura, H., Faroe Channel. Sus-OrpER 3. DriscormpEa. Central capsule and shell discoid or lenticular ; often much flattened. Selected forms : — Trochodiscus heliodes, Cler., North Sea; T. echiniscus, H.; Lethodiscus microporus, H. ; Astrosestrum acanthastrum, H.; Spongodiscus favus, Ehr., Faroe Channel. Susp-Orprer 4. Larcorpea. With lentelliptical central capsule and shell. Selected forms :—Jzthelius minor, North Sea; L. arborescens, H., Faroe Channel ; Phorticiwm pyloniwm, H., Norway and Sweden. Sus-OrpEerR 5. SPHAEROPYLIDEA. With basal or basal and apical pylome (large opening to the shell). See Dreyer (15). Sus-Cuass II]. ACANTHARIA. Radiolaria in which the skeleton is composed neither of the so-called horny acanthin nor of silica, but (in many cases) of strontium sulphate. The central capsule is perforated uniformly or in networks and segregated pores. The skeleton has the form of spicules radiating from a central point within the capsule (Acanthometrida). Rarely a fenestrated extracapsular skeleton is added (Acanthophractida). Orver 1. Acanthometrida. Sup-Orper 1. ActineLiipA. With 10-200 radial or diametral spines not arranged according to Miiller’s Law (p. 132). Famity 1. ASTROLOPHIDAE. Spines radiating from a common centre. Genus 1. Actinelivs. All spines of equal length and similar shape. A. purpureus, H., Mediterranean. Genus 2. Astrolophus. Spines of unequal length. 1 fe) 146 THE RADIOLARIA It is probable that further investigation of the Actineliida will clear up the anomalies that at present attach to their isolated position. They are regarded by Haeckel as the ancestral stock of the whole Radiolaria. The family Litholophidae which he associated with them is now regarded as composed of growth-stages of the genus Acanthonia. Famity 2. ACANTHOCHIASMIDAE. With ten or sixteen diametral spines irregularly arranged. Genus Acanthochiasma. With ten spines, A. fusiforme, found near Plymouth and in the North Sea. A. cructata, A, krohnii, generally distributed in the Atlantic. Sus-OrpEeR 2. ACANTHONIIDA. With twenty spines arranged in four zones of five spines to each (Miiller’s Law). Famity 1. ACANTHOMETRIDAE. Spicules circular in _ transverse section. Genera—Acanthometron ; proximal end of spines without flange ; A. pellucidum, N. and E. Scotland. Phyllostawrus, with flange; Ph. quadrifolius, abundant in North Atlantic. Famity 2. ZyGACANTHIDAE. Spines compressed and double-edged, lanceolate in section. Genus— Zygacantha, without flange at base of spines ; Z. septentrionalis, North Atlantic. Famity 3. ACANTHONTIDAE. Spines cruciform in cross section. Genus — Acanthonia; A. miillerit, N. Scotland and North Sea; A. ligurina, W. coast of Greenland; Acanthonidium ; A. echinoides, North Sea, Faroes and Norway; A. pallidum, N. and E. coasts of Scotland. Famity 4. AMPHILONCHIDAE. ‘Two opposite spines much larger than the rest. Genus—Amphilonche. A. belonoides, generally distributed in the Atlantic. For the exotic family Lithopteridae, see Haeckel’s Monograph (11). OrpDER 2. Acanthophractida. Sus-OrpER 1. SpHAEROPHRACTA. With twenty radial spines of equal size. Shell spherical. Famity 1. SPHAEROCAPSIDAE. Shell composed of very numerous small plates each with a single pore. Genera—l. Sphaerocapsa. Sph. cruciata, Faroes, North Atlantic. 2. Astrocapsa. A. tritonis and A. coronata, Faroes and North Atlantic. 3. Porocapsa. P. murrayana. 4. Cannocapsa. C. osculata, Faroe Channel and North Atlantic. Famity 2. DorataspIpAr. Shell composed of the meeting branches of two to four apophyses given off by the twenty radial spines. Seventeen genera are known, mostly from equatorial or southern waters. Famity 3. PHRACTOPELTIDAE. Shell double; the inner’ one enclosed by the central capsule. No genera known from northern waters. Sup-Orper 2. PrunopHracta. ‘Two or six spines much larger than the rest. Shell not spherical. Famity 1. Betonaspipar. Shell ellipsoidal. Two enlarged spines. The genus Platnaspis occurs in North Atlantic and Mediterranean. Famitry 2. Hexataspipar. Shell lentelliptical. Six enlarged spines. The genus Hexaconus is known from the North Atlantic. Famity 3. Dretoconipar. Shell diploconical with two opposite large funnels (the sheaths of the two enlarged spines). Pseudopodia con- THE RADIOLARIA 147 fined to the two polar apertures. The genus Déploconus is known from the Mediterranean. Sus-Ciass III. Monopynartia (Nassellaria). Radiolaria with monaxonic central capsule that bears at one pole a porous plate forming the base of an inwardly directed cone. Sus-Leaion 1. Plectellaria. Without a complete lattice-shell. OrpeR 1. Piecrormpna. Skeleton a basal tripod (Fig. 5). Selected forms :—Plagiacantha arachnoides, Clap., W. coast of Norway, North Sea ; Plagiocarpa procyrtella, H., North Atlantic, Iceland ; Hexaplagia arctica, H., Greenland ; Polyplagia novenaria, H., Faroe Channel, North Atlantic ; Plectophora arachnoides, H., and Pl. novena, H., North Atlantic and Faroe Channel, North Sea. OrpreR 2. StepHorpEA. Skeleton a sagittal ring, and usually no tripod. Selected forms :—Lithoctrcus annularis, Miill. ; Cortiniscus typicus, H. ; Eucoronis nephrospyris, H. ; all cosmopolitan. Sus-Lecion 2. Cyrtellaria. Skeleton a complete lattice-shell (cephalis). ORDER 1. Spyrorpgea. Cephalis bilocular with cophetin construction. Almost exclusively southern forms. OrpER 2. Borryomprea. Cephalis multilocular. Selected forms :— Botryocampe inflata, Ehr., cosmopolitan ; Phormobotrys hexathalomia, H., Mediterranean. ORDER 3. CyrtorpEA. Cephalis single, without constrictions or lobes. Selected forms :—Tridictyopus elegans, Hert., Mediterranean ; Cornutella clathrata, Ehr., cosmopolitan ; Cyrtocalpis obliqua, H., cosmopolitan ; LIithomelissa thoracites, H., cosmopolitan ; L. setosa, H., Norway ; Hucecry- phalus gegenbauri, H., cosmopolitan ; Carpocanium diadema, H., cosmo- politan ; Dictyocephalus ocellatus, H., Faroe Channel ; Dictyophimus clever, Jorg., Norway; Theoconus ariadnes, H., cosmopolitan : 5 Cladoscentum tricolpium, Norway ; Clathrocyclas craspedota, Norway. Sus-Cuiass IV. TRIPYLARIA (Phaeodaria). Radiolaria in which the central capsule is double and usually possesses a chief aperture (astropyle) and two accessory apertures (para- pyles). A dense resistant pigment (phaeodium), probably of excretory nature, accumulates in the extracapsulum. ‘The skeleton is siliceous and often made up of hollow tubes. OrDER 1. Phaeocystina. The skeleton consists of isolated spicules. Famity 1. AULACANTHIDAE. Skeleton of tangential needles and radial hollow rods. Selected forms :—Aulacantha scolymantha, H., Hebrides, 148 THE RADIOLARIA Faroe Channel, Shetlands ; Aulographis zetesios, Borg.; A. furcellata, Wolf., Faroe Channel ; Aw. tetrancistra, H., Norway ; Aulodendron boreale, Wolf., Faroe Channel. : ORDER 2, Phaeosphaeria. Skeleton composed of an extracapsular shell or of two concentric shells separated by the extracapsulum. Outer shell usually spherical. FamMILy 1. SaGOSPHAERIDAE. Outer shell a lattice-work with triangular or areolar meshes. Selected forms :—Sagena ternaria, H. ; Sagosphaera trigonilla, H., cosmopolitan ; Sagenoarium sp., Jorg, Norway. Famity 2. AULOSPHAERIDAE. An outer lattice-shell alone present, the hollow bars of which contain septa. Selected forms :—Awulosphaera flecuosa, H., Faroe Channel ; Auloscena verticillatus, H., Norway ; Aulotractus fusulus, H., Faroe Channel, Hebrides. FaMILy 3. CANNOSPHAERIDAE. Inner and outer lattice-shells present, interconnected by radii. Cannosphaera antarctica, H., bipolar form. Famity 4. PorospaTHIDAE. Inner shell alone present, composed of two finely grained membranes ; elliptical or ovoid. Mouth at the end of a curved process. ORDER 3. Phaeogromia. A single simple shell present, variable in shape, but always provided with a projecting peristome. FamIty 1. CHALLENGERIDAE. Shell monaxonic, composed of two layers which exhibit an extremely fine diatomaceous graining. Peristome toothed. Selected forms :—Lithogromia silicea, H., Faroe Channel; Protocystis tritonis, H., Faroe Channel, Shetlands, North Sea; Pr. tridens, H., Norway and Sweden; Pr. harstont, Murray, Norway ; Pr. xuphodon, H., Faroe Channel; Challengeron trioden, balfourt, golfense, johannis, armatum (Fig. 27); Cadiuwm melo, Clev.; Pharyngella gastrula, H.; Entocannula hirsuta, H. ; Faroe Channel. Famity 2. Mrepusertipar. Primary Challengeron armatum, Borg. xX 225. q C : The mouth (M) of the perforated shell is shell alveolar. Peristome with articulated surrounded by procearessang.ts abere! feet, A secondary shell may be developed capsule possesses two astropyles (As), in relation to the phaeodium. two parapyies, and two nucle. The 4. Small forms (averaging Ol mm. (From a living specimon, after Borgert.) jn diam.), with primary shell and few radial spines. Phaeodium in primary shell. Huphysetta nathorsti, Clev., North Sea, Scotland; Medusette tiara, H., Faroe Channel. B. Small forms (0°8-°3 mm.), with hooded primary shell provided Fria. 27. THE RADIOLARIA 149 with six long radial spines. Phaeodium still in the primary shell. Gazelletta, Fowler. (. Large forms, with conical shell, completely filled by central Fia. 28. Atlanticella craspedota, Borgert. In this newly discovered family of Phaeo- daria the central capsule (C.c) is a large inflated 4-lobate structure. The skeleton consists of a me- dian hollow part (7.Sk) and of four pendent septate arms (Sp). The black area is the phaeodium (Ph). x 50. (After Borgert.) capsule, which is converted into a swim-bladder. A diaphragm, perfor- ated (Hicker [37]) by several astropyles and parapyles, separates endoplasm from ectoplasm (Fig. 12). Phaeodium outside primary Fic. 29. Planktonetta atlantica, Borgert. (After Fowler.) x 66. The entire animal is shown as seen in a pre- served specimen. One pair of arms is omitted. The central capsule (End) is invested by a skeletal membrane and forms a fioat. The arms are embedded in the phaeo- dium (Ph) and attached to this is the outer shell (F), comparable with that of Medusetta and Atlanti- cella. A section through this animal is seen at Fig. 12, p. 120. shell, with intra-phaeodial skeleton. A float present. Planktonetta atlantica, Borg., Faroe Channel (29, 37). D. Large forms, without primary shell. Central capsule a swim- bladder. Diaphragm and phaeodial skeleton as in preceding sub-family. Secondary shell projecting over peristome. No float. Nationaletta. 150 THE RADIOLARIA E. Mid-sized forms, without primary shell. Secondary shell with four arms. Aflanticella. (Fig. 28.) Borgert (21). Famity 3. CASTANELLIDAE. Primary shell two-layered and com- posed of (1) extremely delicate tangential siliceous needles; (2) the two conjoined limiting membranes of the two layers, united by (3) a porcellanous impregnation. Selected form :— Castanidiwm apsteint, bipolar (36). Famity 4. CrrcoportpaE. Shell composed as in Family 3, but spherical, polyhedral, or multipolar (36). Famity 5. TuscaRoripar (Fig. 30). Shell rarely spherical, gener- ally monaxonic. Nucleus elongated with sigmoid chromatin band. (Borgert [21a].) Fia. 30. Tuscaroridae. A, Tuscarusa globosa, Borgert, showing the peristomial hollow spines ; the rest are broken off. x 39. B, Tuscarora nationalis, Borgert, showing the two central capsules in the shell. Each capsule contains a bent nucleus. x 24. (After Borgert.) OrperR 4. Phaeoconchia, H. Central portion of the skeleton in the form of two valves, free or hinged together. Faminy 1, ConcHartpak, H. With thick valves, which are devoid of an apical cupola and of radial tubes. Equatorial and southern forms. 2 Famity 2. CogLOpENDRIDAE. With extremely thin valves, each of which bears a cupola and tubular processes. Coelodendron ramosissimum, Faroe Channel and cosmopolitan. Famity 3. Comnograputpan, Each cupola provided with a hollow process (rhizocanna), which communicates with the cupola by a paired or unpaired frenulum. Radial tubes strongly developed, sometimes forming an outer bivalved mantle. The largest and most complex eee! ee ee THE RADIOLARIA 151 Fia. 31. Coelothamnus davidofii, Biitschli; one of the Phaeodaria. Entire animal drawn from a dead specimen. xX 4. Sixteen radii spring from the bivalve shell (S) which encloses the central capsule. The ectoplasm (£) is shown investing the skeleton which supports it on the anchor- like extremities of its tufted appendages. (After Biitschli.) Radiolaria (20-30 mm. in diam.). Selected forms : — Coeloplegma murrayanum, H. (Fig. 32); C. tritonis, H., Faroe Channel. : Fic. 82. Central capsule and adjacent structures of Coeloplegma murrayanum, H.; one of the Coelo- graphidae. The bivalve shell (S) supports the hollow-branched galea (@), in which the phaeo- dellae are seen emerging through the aperture (2) of the nasal tube (rhizocanna). The astropyle (As) is drawn out into a tube. LITERATURE. 1. Ehrenberg, Ch. G. Monatsberichte d. Berliner Akad. 1844-73. 2. (Fossil Species.) Abhandl. d. k. Akad. Berlin, 1872, pp. 131-397. 38. Huxley, T. H. (Thalassicolla.) Annals and Mag. Nat. Hist. vol. Viii., 1851, pp. 433-442. . 152 LITERATURE OF THE RADIOLARIA 4, Miiller, J. (Fundamental Treatise.) Abhandl. d. Berliner Akad. 1858, pp. 1-62. 5. Haeckel, E. Die Radiolarien. Berlin, 1862. 6. Cienkowski. (YellowCells.) Archiv f. mikros. Anat. vii., 1871, pp. 372-381. 7. Hertwig, R. (Structure of Radiolaria.) Jenaische Denkschriften, vol. ii., 1879, pp. 129-277. 8. Biitschli, O. (Skeleton of Nassellaria.) Zeit. f. wiss. Zool. vol. xxxvi., 1881, pp. 485-540. (Monograph.) Bronn’s Thierreich, Protozoa, vol. i., 1885, pp. 332-478. 10. Brandt, K. (Sphaerozoa.) Fauna y. Flora d. Golfes von Neapel, vol. xiii., 1885. 10a. (Zooxanthellae.) Mittheil. Stat. Neapel, iv., 1883. 11. Haeckel, E. (Monograph.) Challenger Reports, vol. xviii., 1887. 12. Lankester, E. Ray. MRadiolaria in Encyclopaedia Britannica, Art. ** Protozoa,” pp. 20-23 of reprint. 13. Famintzin, A. (Life-History, Food, and Yellow Cells of Sphaerozoa.) Mémoires de ]'Acad. Sci. St. Pétersbourg, 7th series, vol. xxxvi. No. 16, 1889, p. 21. 14. Verworn. (Thalassicolla.) Pfliiger’s Archiv f. Physiologie, vol. li., 1891, p- 118. 14a. (Hydrostatics.) bid. vol. liii., 1893, pp. 140-155. 15. Dreyer, F. (Evolution of Radiolarian Skeleton.) Jenaische Zeit. f. Naturwiss. vol. xxvi., 1892, pp. 204-468. 16. Karawiew. (Fission in Aulacantha.) Mém. Soc. Natur. Kiew. vol. xv., 1896. 17. Borgert, A. (Reproduction of Tripylaria.) Annals and Mag. Nat. Hist. (6), xviii, 1896, pp. 422-426. 18. —— (Fission in Aulacantha.) Spengel’s Zool. Jahrb. Anat. vol. xiv., 1900, pp. 203-274. 19. —— (North Atlantic Tripylaria.) Nordisches Plankton, Lief. i, 1901, pp. 1-52. 20. —— (Tripylaria of the German Plankton Expedition.) Zool. Jahr. Syst. vol. xix., 1904, pp. 733-760. 21. (Atlanticellida.) Ergeb. Plankton-Expedition, vol. iii., 1906. 21a. (Tuscaroridae.) Jbid. vol. iii., 1906. 22. Vernon, H. M. (Respiration in Collozowm.) Journal of Physiology, . vol. xxi., 1897, p. 443. 23. Brandt, K. (Bionomics of Acantharia.) Ergebnisse d. deutschen Plankton- Expedition, vol. i., 1892, p. 338. 24. (Hydrostatics.) Zool. Jahrbiicher Syst. vol. ix., 1895, pp. 27-74. 25. —— (Thalassophysidae.) Archiv f. Protistenkunde, vol. i., 1902. 25a. —— (Division of Thalassicolla.) Mitteil. d. Vereins Schlesw.-Holstein. Aerzte, 12. Heft, 1890. 26. —— (Thalassicollidae.) Ibid. vol. vi., 1905, pp. 245-271. 27. —— (Classification of Sphaerozoa.) Zool. Jahrb. Suppl. vol. viii., 1905, pp. 311-352. 28. Wolfenden, R. N. (Radiolaria of Faroe Channel and Shetlands.) Journal Marine Biol. Assoc. N.S. vol. vi., 1902, No. 3. Trans. Linn. Soc. vol. x., pt. 4, 1905. 29. Fowler, G. H. (Planktonetta.) Quart. Journ, Mic. Sci. (2), vol, xlvii., 1903, pp. 133-143. LITERATURE OF THE RADIOLAKIA 153 80. Fowler, G. H. (Gazelletta.) Quart. Journ. Mic. Sci. (2), vol. xlvili., 1904, pp. 488-488. 31. —— (Radiolaria of Faroe Channel.) Proc. Zool. Soc. 1896-98, pp. 991, 523, 1016. 3la. Popowsky, A. (North Atlantic Acantharia.) Nordisches Plankton, Lief. lii., 1905, pp. 43-69; Lief. v., 1906. 82. —— (Acantharia.) Ergeb. Plankton- Expedition, 1904; Appendix in Archiv f. Protistenkunde, vol. v., 1905, pp. 339-357. 33. Schewiakoff, W. (Skeleton, Myonemes, and Flotation of Acantharia.) Mémoires de ]’Acad. des Sci. St. Pétersbourg, vol. xii., 1902, No. 10. 34. Immermann, F. (Aulacanthidae.) Ergeb. Plankton-Expedition, vol. iii., 1904. 85. Hdcker, V. (Biological Significance of Tripylarian Skeleton.) Jenaische Zeitschrift f. Naturwiss. vol. xxxix., 1905, pp. 581-648; Zeit. f. wiss. Zool. vol. Ixxxiii., 1905, pp. 336-375 ; Archiv f. Protistenkunde, vol. ix., 1907, pp. 139-169. 36. —— (Challengeridae, Tuscaroridae, Circoporidae of the Valdivia Expedi- tion.) Archiv f. Protistenkunde, vol. viii., 1906 ; and Verhandl. deutsch. zool. Gesellschaft, vol. xiv., 1906, pp. 122-156. (Thalassothamnidae, Medusettidae.) Zool. Anzeiger, vol. xxx., 1906, No. 26, pp. 878-895 (16 figs.). 38. Schréder, O. (Cytocladus.) Zool. Anzeiger, vol. xxx., 1906, pp. 448 and 37. 587. 39. Biitschli, G. (Strontium Sulphate in Skeleton of Acantharia, etc.) Zool. Anzeiger, vol. xxx., 1906, No. 24, pp. 784-789. 40. Delap, M. and C. (Irish Thalassicollidae.) Scientific Investigations, Irish Fisheries, 1905 (vii.) [1906]. 41. Keeble, F., and Gamble, F. W. (Green Cells of Convoluta.) Quart. Journ. Micr. Sci. vol. li., 1907, pp. 167-219. 42. Schaudinn, F. (Trichosphaerium.) Abhandl. d. kgl. preuss. Akad. Wiss. Berlin, Supplement, 1899. 43. Pitter, H. (Respiration of Protozoa.) Zeit. f. allgemeine Physiologie, vol. v., 1905, pp. 5664612. Jbid. vol. vii. pp. 46-53. 44, Hinde, J. G. (Fossil Radiolaria.) Quart. Journ. Geol. Soc. vol. lv. pp. 38-64. 45. Johnstone, J. (Summary of Recent Work on Marine Nitrogenous Food- Stuffs.) Science Progress (N.S.), vol. ii., 1907, pp. 191-210. 46, Klebs, G. (Yellow Cells and Peridinians.) Bot. Zeitung, vol. xlii., 1884, Pratl. THE PROTOZOA (continued) SECTION F.—THE MASTIGOPHORA * CLASS MASTIGOPHORA. Syp-Ciass I. LisSOFLAGELLATA. Order 1. Monadidea. Tribe 1. Pantostomatina. Sub-Tribe 1. Holomastigoda. ¥ 2. Rhizomastigoda. Tribe 2. Protomastigina. Sub-Tribe 1. Monomastigoda. 2. Paramastigoda. 8 Heteromastigoda. ra 4, Isomastigoda. Tribe 3. Polymastigina. Sub-Tribe 1. Trimastigina. 2. Monostomatina. 3. Distomatina. 4. Lophomonadina. Order 2. Buglenoidea. Tribe 1. Buglenina. 9. Astasiina. , 93. Peranemina. Order 3. Chromomonadidea. Tribe 1. Chloromonadina. 2. Chrysomonadina. a a Cryptomonadina. Sup-CLAss II. CHOANOFLAGELLATA, Order 1. Craspedomonadina. aa? Phalansteriina. Sup-CLass III. PHyTOFLAGELLATA. Order 1. Chlamydomonadina. » 2. Volvocina. Sup-CLass IV. DINOFLAGELLATA. Tribe 1. Gymmnodiniaceae. 2. Prorocentraceae. , 3. Peridiniaceae. Sup-CLass V. CYSTOFLAGELLATA, Sup-CLAss VI. SILICOFLAGELLATA. +P] ”? >P] ”? ”? ”? ” 1 By Arthur Willey, 154 F.R.S., and Prof, 5. J. Hickson, F.R.S. eh Tis id THE MASTIGOPHORA 155 ‘THE unicellular organisms which are associated in the class Mastigo- phora or Flagellata in the wide sense, comprise a very heterogeneous assemblage of forms, having in common the possession of certain characteristic traits of organisation (a single nucleus, one or more contractile vacuoles, one or more flagella), and further united together phyletically by the occurrence of transitional or annectant types. Our knowledge of the group dates back to the time of Anton Leeuwenhoek, at the beginning of the eighteenth century, while the foundation of the modern system may be safely attributed to the labours of Christian Gottfried Ehrenberg during the early part of last century (1830-1838). From the most general point of view the peculiar biological interest of the Mastigophora rests upon the fact that, in this more than in any other class of Protista, the formal distinctions which are commonly drawn between the animal and vegetable kingdoms vanish. It was formerly a question whether such and such an order of Mastigophora should be reckoned among the unicellular Algae or among the Protozoa, but this controversy is now practi- cally over, and biological disquisitions upon the group are equally at home and equally necessary in zoological and botanical treatises and journals. When an organism possesses a green colour, due to the presence of chloroplasts stained with chlorophyll, has a cell-wall that gives the chemical reactions of cellulose, and is devoid of a mouth for the ingestion of solid food, it is usually regarded as a plant. When, on the other hand, an organism bears no chlorophyll, has no cell- wall, or has a cell-wall that does not give the cellulose reaction, and possesses a mouth for the ingestion mB solid food, it is usually regarded as an animal. If it were possible to divide the Mastigophora into two divisions, one containing all those forms provided with a mouth and devoid of chlorophyll and a cellulose cell-wall; and the other containing all those forms without a mouth, bearing chlorophyll and surrounded by a cellulose cell-wall, then the former division could be assigned to the animal kingdom and the latter to the vegetable kingdom. Such a division would, however, be thoroughly un- scientific and unnatural. It could only be made by deliberately ignoring obvious genetic relationships. Moreover, such a division would leave out of account a number of organisms—particularly Monadidea—which fail to fulfil all the conditions for their admission into either of the divisions. It is not by the study of any one stage of the life-history of these organisms that it is possible to arrive at any clear conception of the best distinction that can be drawn between the animal and vegetable kingdoms. The study of the whole life-history of some of the lower 156 THE MASTIGOPHORA animals and plants, however, suggests a line of distinction which is perhaps more in accordance with a natural system of classification. In the life-history of Ulothriz, one of the Ulotrichaceae, an example of an organism that is universally regarded as a plant, we find two forms of cells. There are the cells of the filamentous thallus, protected by a cell-wall, containing chlorophyll, and, under favourable conditions, growing and increasing in number by fission ; and there are the cells provided with two or four flagella that escape from their cellulose investments and eventually conjugate to form a motionless zygospore. If we compare this with the life-history of such a form as Mastigella, one of the Mastigophora that is universally regarded as an animal, we find that during the phase of life when growth and repeated multiplication by fission occurs the organism is actively moving about by means of its flagellum or its pseudopodia, and that the gametes that it gives rise to are also active and flagellate. Any period in the life-history of Mastigella when active movements cease is not, as in the case of Ulothriz, a period of vegetative growth. If we regard, then, as marks of distinction between an animal and a plant (1) that the stage of growth and reproduction of somatic cells by fission is marked by a period of active mobility in the former, and of stability in the latter ; and (2) that the flagellate cells of the latter do not grow and divide by fission, but conjugate and give rise immediately to a sedentary zygospore, whereas in the former the flagellate cells may grow and divide by fission, we represent a consideration which has had considerable weight in determining the action of zoologists in including the Mastigophora in the animal kingdom. But the boundary thus drawn, even if it is the best that can be drawn, is itself subject to some exceptions. In some of the Chlamydomonadina we find, for example, that flagellate individuals similar in general characters to the gametes form a gelatinous investment, withdraw their flagella, grow and divide repeatedly by fission. It is difficult to distinguish this phase of life (the “ palmella-stage,” as it is called) from a true plant under the terms of our definition. The close relation of the Chlamy- domonadina to the Chromomonadina, however, is so clear that to separate them by placing one order in the vegetable kingdom and the other in the animal kingdom on this ground alone would be absurd, The life-history of the Chlamydomonadina seems to support very strongly the view that some of the families of the lower Algae have sprung from a flagellate ancestry, but it does not justify the assumption that the vegetable kingdom as a whole owes its origin to the class Mastigophora.! ' See Blackman and Tanslefy (2), and West (22, pp. 32 e¢ seq.). THE MASTIGOPHORA 157 It is principally in respect of their modes of nutrition that the Mastigophora appear to betray the mixed animal and vegetable properties, so that as a class they have come to be regarded as mixotrophic micro-organisms. ‘The four possible methods of ali- mentation—holozoic, parasitic, saprophytic, and holophytic—are all to be met with among the members of this protean series, either separately or in combination. When a single species can vary its metabolism in adaptation to its immediate environment, for example, according as it is exposed to or deprived of the influence of light, it is said to be mixotrophic in the strict sense of the term (Pfeffer). It is not always easy to assert positively in what manner food is conveyed into the protoplast (protoplasmic body of the cell), but it is certain that holozoic nutrition is often associated in the same species with saprophytic (Monadidea), saprophytic with parasitic, saprophytic with holophytic (Euglenoidea), and, more rarely, holozoic with holophytic (Chromulina). Sometimes three methods are found in combination—holozoic, saprophytic, and holophytic (Ochromonas). It may be stated as a general rule that all Lisso- flagellata (z.¢. true Flagellata in the restricted sense) are capable of saprophytic nutrition, that is to say, of absorbing nutriment from putrescent substances in an aqueous medium, but that this source of food is usually accessory to some other essential means of nourishment. Where saprophytism is the sole condition of exist- ence, as in the case of the Astasiina, there is reason to regard it as a secondary state derived, in the particular instance quoted, from a condition of holophytism. The parasitic forms may be described broadly as falling into three categories : ectoparasites (Costa, Stylochrysalis, Silicoflagellata) ; endoparasites (species of Hexamitus, Megastoma, Tetramitus, Tricho- mastiz, Trichomonas, Trichonymphidae); and haematozoa (7'rypano- soma, Herpetomonas). The non-parasitic Mastigophora are either free-swimming or sessile, solitary or colonial in habit. Some species are capable of temporary fixation by means of a protoplasmic stalk either of pseudopodial (e.g. Oicomonas sp., Fig. 5 (31)) or of flagellar (e.g. Bodo sp.) origin. Some solitary free forms are closely related to solitary fixed forms (e.g. Huglena and Ascoglena), and many free-swimming colonial genera have sessile representatives: _ (e.g. Dinobryon and Hyalobryon). The form of association of individuals in the colonies varies within limits, and there is a great amount of parallelism in this respect between members of different orders. An entire colony or coenobhium may attain to a certain degree of individuation, which is. most marked in the Volvocina, but is not wanting in other groups, as is evident from the co-ordinated movements which they execute and from the fact that the whole coenobium may undergo binary 158 THE MASTIGOPHORA fission (Uroglena). On the other hand, the units often retain a facultative independence, and the coenobium may then undergo dissociation (Synura). The principal forms of association of individuals are the follow- ing :—1. Linear aggregates, e.g. Hirmidium, Chlorodesmus, Ceratium ; 2. Rosettes, ¢.g. Bicosoeca socialis, Cyclonexis annularis, Gonium pectorale ; 3. Plates, e.g. Proterospongia, Platydorina ; 4. Spherical aggregates, e.g. Sphaeroeca, Uroglena, Volvoz ; 5. Dendroid associations, ¢.g. Dinobryon, Hyalobryon, Poteriodendron, Anthophysa, Rhipidodendron, Dendromonas, Phalansterium. Of the above colonial assemblages it is to be remarked that the dendroid form is the most polymorphic in actual appearance. As for transitional forms, it is not difficult to construct a series, while analogies are stupefying in their abundance. ‘Thus a biserial linear ageregate like Chlorodesmus in comparison with a rosette like Cyclo- nexis is absolutely paralleled by species of the pelagic Ascidian, Salpa. A transition from a rosette to a plate is afforded by Gonzwm, and from a rosette to a spherical aggregate by the volvocine genus Stephanosphaera, in which the units are arranged in a rosette though surrounded by a common gelatinous envelope. The Mastigophora as a class may be defined broadly as uni- nucleated Protista which perform their movements by means of one, two, or several flagella, usually arising at or near the anterior end, i.e. the end which is directed forwards during locomotion. The typical motion of the flagellum has been described as one of circumduction (Delage), by which the cell is drawn along at the same time that it rotates about its axis. The flagellum of a typical Flagellate Infusorian is therefore a tractellum, as opposed to the tail of a spermatozoan, which is a pulsellum.! It acts, however, as a pulsellum in exceptional cases among the Monadidea, and with the Choano- flagellata when they quit their attachment in order to effect change of position. According to the number, position, and proportions of the flagella we recognise monomastigote forms, with a single porrect flagellum ; paramastigote, with one or two small accessory flagella at the base of the main one ; isomastigote, with from two to four equal flagella; heteromastigote, with divergent flagella, one directed forwards or transversely, the other directed backwards ; polymastigote, with more than four flagella ; to which may be added holomastigote forms, with numerous flagella distributed over the entire surface of the cell. The disposition of the flagella has a distinct systematic importance, but of much more limited application than was formerly 1 The terms “tractellum” and “ pulsellum” were suggested by Prof. Lankester, In some elongate metabolic species (Astasiina) the tractellum is directed straight forwards, and only the apical portion of it executes rapid vibrations, drawing the body along without rotation. eal! et > afk ood THE MASTIGOPHORA 15g supposed, since the phenomenon of parallelism is as strikingly dis- played in this respect as in the manner of formation of colonies. The heteromastigote condition merits particular notice since it characterises an -entire sub-class (Dinoflagellata), where the one flagellum is transverse, usually lying in an annular depression, while the other is longitudinal and is also partially protected by a groove, but extends backwards freely (Fig. 10). This is a special mani- festation of the heteromastigote condition, but equally interesting examples occur in many families of Lissoflagellata, where the anterior flagellum is normally directed forwards (tractellum) and the posterior flagellum which arises from the body of the cell close to the former is trailed behind. The posterior flagellum in these cases exerts a directive and modifying influence upon the move- ments of the Infusorian, serving also as an anchor and sometimes as a spring promoting a rapid jerking movement of leaps and bounds like the tail of a Podurid. The posterior flagellum of heteromastigote Mastigophora may be aptly described as a gubernaculum (Fig. 7 (10)) and referred to by that term. The flagellum is usually so extremely attenuated that it is very difficult to discover any structure in it, but as its base may often be traced from the surface through the ectoplasm to the endoplasm, it seems probable that it consists of an axial filament derived from the endoplasm and a delicate cortical sheath derived from the ecto- plasm. It is interesting to note that in the KRhizomastigoda there is an endoplastic axial filament in the pseudo- podia (Fig. 1). It is impossible to draw any morphological line of dis- tinction between a flagellum and a cilium, and in the Lophomonadina, for example, the vibratile processes have eae been interpreted as flagella by those anteriorend of an wating wagemat. who regard this group as belonging 2° syd trom the endoplasm to the Mastigophora and as cilia by fee UL eee Beeudapodia (os); Jy ieee! those who regard it as a family of voir. Px 660. (Alter Goldschmidt.) Infusoria. Since the discovery that the equatorial groove of the Dinoflagellata (p. 182) is not ciliated, it is usually regarded as a character of the class that true cilia do not occur ; and if the vibratile processes of the Polymastigina are true flagella, the only exception to this is to be found in the aberrant genera Pteridomonas, Maupasia, and Monomastix (pp. 164 and 17 0). As a rule, there seems to be no connection between the base of the flagellum and the nucleus, but such a connection can be traced 160 THE MASTIGOPHORA in the genera Mastigamoeba and Mastigina, recalling the relation of the axial filament to the nucleus in certain Heliozoa (p. 23). At the base of the axial filament there is sometimes found a minute granule, with peculiar staining properties, known as the blepharoblast (Fig. 2, ), and closely associated with this there is in the Trypanosomata’ a small detached portion of the nucleus known as the “ kineto- nucleus.” At the base of the flagellum there is often found a special vacuole into which the con- tractile vacuoles may or may not open (Figs. 1 and 2). This is the flagellar reservoir. In some forms (Zvichomenas and Trypanoso- mata) a delicate undulating membrane is. found at one side of the flagellum (Fig. 2, p. 195). Besides the flagellate movements there are two other important ways by which locomotion can be effected by certain species, namely, by amoeboid and by so-called metabolic or euglenoid changes of shape, the former resulting in the protrusion of pseudopodia, and the latter involving alternate protraction and contraction of the body, as may be observed in many Fia. 2. Diagram of the struc- ture of Copromonas. |, blepharoblast; ¢.p, cyto- pharynx; c.st, cytostome ; worms (Fig. 5 (28)). The possibility of executing amoeboid and metabolic movements depends largely upon the nature of the integument or pellicle which c.v, contractile vacuole ; fl, flagellum; fv, food- vacuoles; N, nucleus; R&, (After protects the protoplast from the surrounding fluid medium. There are three principal kinds of integu- ment, with many degrees of differentiation :— 1. Periplast.—This is an integral portion of the protoplast, from which it is never separated and with which it divides. In naked cells, such as Mastigamoeba, it appears as a simple ectoplasm covered by a very thin pellicle (Fig. 1, pel), or as an alveolar layer of proto- plasm (JMJulticilia). In most cases there is a more or less well- defined pellicle or plasmatic membrane, which may be distinguished under the name of proteid-membrane. This achieves its highest development in the Euglenoidea, where it often presents a spirally striated structure and resists decomposition (Fig. 5 (16, 17)). 2. Perisare.—The perisare does not, as a rule, form an integral part of the protoplast, and does not usually divide with it, so that after the division of the protoplast one of the fission-products issues flagellar reservoir. Dobell.) 1 For a discussion of the relations of these structures compare Dobell (3), Minchin (13), Moore (14), Hartman and von Prowazek (5). THE MASTIGOPHORA 161 from the perisare as a naked cell. The protoplast is never com- pletely adherent to its perisarc, but is capable of more or less independent movement within it, and recedes from it upon the formation of the resting-stage, and also in consequence of plasmo- lysis. Its chemical composition is based upon a gelatinous substance of carbohydrate nature, and in Dinobryon Klebs has found that the perisare gives the typical cellulose reaction. The periplast is always present in Lissoflagellates, but the perisare is a secondary formation secreted by the protoplast through the periplast, and may or may not be present. The perisare may occur as a capsule closely investing the cell with an apical opening for the flagellum, as in Chrysococcus and Trachelomonas. In the Chrysomonadine genera Synura, Mallomonas, HHymenomonas, and Microglena the protoplast is closely adherent to the perisare, which here tends in the direction of a true cell-wall and is called a cuticle. In Hymenomonas by exception the perisare divides with the cell. The most familiar form in which the perisare is developed is that of a cupule, as in the calyptoblastic Hydroids. Well-known examples of cupule-formation are presented by the genera Licosoeca, Poteriodendron, Salpingoeca (Fig. 7 (6,7)), Dinobryon, ete. Some genera secrete a stalk only, without a cupule, of which Anthophysa and Cephalothamnion are among the best-known examples. 3. Cell-Wall.—This stands in intimate relation with the proto- plast, as in Algae and higher plants, so that the cell-body has no independent movement, apart from the automatic streaming of granules. The cell-wall may (Dinoflagellata) or may not (Volvo- caceae and Coccolithophoridae) divide with the protoplast. Its chemical composition resembles that of the perisare, and in the Dino- flagellata consists of cellulose. In the Coccolithophoridae the cell- wall is built up of several shells composed of calcium carbonate. Nucleus.—The nucleus of the Mastigophora shows many varie- ties of intimate structure. In some cases the chromatin is dis- tributed in the form of a simple chromatic network (LHerpeto- monas), in others (Bodo, Copro- monas, Fig. 2) the chromatin is . present in the form of a central or R%0,,tages im the mitosis of the nucleus lump or mass, Tn Euglena there (© beaming tniate previo to division Ss sires 9 . /B, s wrapped roun is within the nuclear membrane the central part of the archoplasmic body, and separate chromatin masses, and Sth eens Sci Ome i in addition a substance which has been variously interpreted, but is usually known as the EratS; II 162 THE MASTIGOPHORA “nucleolar centrosome.” In Noctiluca (Fig. 3) an archoplasmic body situated outside the membrane accompanies the nucleus and gives rise to the achromatic spindle of the mitotic figure. Mitotic division of the nucleus has been described in a large number of cases taken from all the principal divisions of the group, but it is certain that in some cases nuclear division occurs by amitosis (Copromonas and others, Dobell [3]). Nuclear reduction in the for- mation of the gametes has been observed in some cases (Trichomonas, Bodo, Hexamitus, Copromonas, and others). Notwithstanding the great variety of structure and mode of division of the nuclei in the Mastigophora, there is no evidence that in any case a division of the nuclear substance takes place into a somatic nucleus and sexual nucleus, comparable with the mega- nucleus and micro-nucleus of the Infusoria (Heterokaryota). The separation of the kineto-nucleus from the main nucleus in the Trypanosomata may suggest that in this case there is a delegation of special functions in connection with the flagellum to a detached portion of the nucleus; but apart from this all the Mastigophora are in the strictest sense Homokaryota (Hickson). The life-history of the organisms comprised by the class Mastigophora shows so many varieties that no general principles can be laid down in this place. The life-histories of several forms are described in the account given of the various subdivisions of the group. The great advance in our knowledge of these forms that has been made during the past few years suggests that a process of gametogenesis followed by conjugation of the gametes occurs in the life-histories of all the orders. The Mastigophora are an important component of the micro- plankton of oceanic and lacustrine waters. The Dinoflagellata together with the Algae of the natural order Bacillariaceae, to which the former appear to be more or less closely related, are said to constitute the bulk of the primary food-supply (Urnahrung) of the sea [Schiitt]. It is customary, in the more recent treatises, to employ the term Flagellata in a restricted sense, equivalent to the Lissoflagellata of Lankester, with the inclusion of the Choanoflagellata. In this sense also the term Euflagellata has been employed, and the flagellate members of the freshwater plankton comprise Euflagellate, Dinoflagellate, and Phytoflagellate' forms. The marine plankton comprises in addition the Cystoflagellata and the Coccolitho- phoridae. It is in order to avoid possible confusion that the term Mastigo- phora, introduced by Diesing in 1866, is employed to designate the entire group of flagellate organisms. 1 Sometimes the Phytoflagellata are comprehended within the Euflagellata, but this tends to misapprehension, ok NE ae gy? eee LENS etwas os THE MASTIGOPHORA 163 The six sub-classes of Mastigophora may be tabulated as follows :— Sub-Class 1. Lissoflagellata Choanoflagellata Phytoflagellata (Volvocaceae). Dinoflagellata (Peridiniales). Cystoflagellata. Silicoflagellata. Kuflagellata. Ste Co be The Euflagellata are defined as Protozoa which possess a sharply defined, uninuclear sarcode, whose periplast is either a simple ectoplasm or a definite pellicle. During the greater portion of their life they are in motion, or at least capable of motion. They have a definite anterior end, from which one, two, or many flagella arise, and they possess one contractile vacuole or several. Repro- duction takes place by simple longitudinal fission,’ generally in the flagellate condition, sometimes in a resting condition. It seems probable that most of the Euflagellata are capable of forming resistent cysts, usually called sporocysts. The occurrence of a process of conjugation was asserted by Dallinger and Drysdale and others of the earlier observers, but some doubt was thrown upon the accuracy of these statements by Biitschli and Senn. In recent years, however, the formation of definite gametes and a process of conjugation have been proved to occur in WMastigella by Goldschmidt (4), in Pseudospora by Robertson (18), in Monas and Bodo by von Prowazek (16), in Copromas by Dobell (3), and in Trypanosoma and other forms by Schaudinn (19). There seems to be little doubt, therefore, that conjugation is a normal process in the life-history of all the Euflagellata. Sus-CLass J. LISSOFLAGELLATA, Lankester. The members of this sub-class are distinguished from the other Euflagellata by the absence of a collar. The sub-class is divided into the three orders: 1. Monadidea. 2. Euglenoidea. 3. Chromomonadidea. ORDER 1. Monadidea, Biitschli. The Monadidea comprise the least differentiated forms of Mastigophora, and include genera that exhibit affinities with the Proteomyxa (Multicilia, Pseudospora, p. 8), with the Lobosa (Rhizo- 1 Cases of true transverse fission are very rare among the Lisso- and Choano- flagellates ; e.g. Oxyrrhis, Stylochrysalis, Phalansterium. 164 THE MASTIGOPHORA mastigoda), and possibly also with the Heliozoa (Dimorpha). ‘They are colourless Flagellata with one to an indefinite number of flagella, a simple vacuole system, and usually a single nucleus. Their nutrition may be holozoic, parasitic, or saprophytic, but probably never holophytie. TRIBE 1. PANTOSTOMATINA, Senn. Solid food may be ingested at all points in an amoeboid fashion. Sus-Trise 1. Hotomasticopa, Lauterborn. With polyaxonic body, flagella scattered all over the surface, pseudopodial ingestion of food, loco- motion rotatory, defaecation at all points. Multicilia, Cienkowski; M. marina, Cienk., with one nucleus; M. lacustris, Lauterborn, plurinuclear, the only instance of the kind among Mastigophora. The genus Grassta, Fisch., closely allied to Multiczlia, is found in the alimentary canal of the frog and in the blood of Hyla. Sup-Trise 2. Ratzomasticopa, F. E.Schultze. With one or two flagella, natant and amoeboid or heliozooid phases. The flagella persist through the amoeboid or heliozooid phase. The monomastigote and dimastigote genera present a parallel series, and in addition there is an aberrant genus, Pteridomonas, Penard, in which there is a circlet of 8-12 cilia, which can be rolled inwards like a watch-spring and then bent outwards, exerting a jerking action by which the animal hops backwards. These cilia surround the base of the single main flagellum. In the genus Mastigamoeba the flagellum arises directly from the nucleus. The genus Mastigina (Frenzel) is closely related to Mastigamoeba, but the body is covered with a thick pellicle. The position of Mastigella, Frenzel (Fig. 4), is more difficult to determine, as there may be one or more flagella which are quite independent of the nucleus. In Mastigamoeba schulzei (Frenzel) and Mastigina setosa (Goldschmidt) the body is thickly beset with long rigid bristles which have the general appearance of cilia, but seem to have the same nature as the adhesive granules (Klebkérner) with which the pellicle and superficial ectoplasm of several species of the three genera are provided. It is possible that they are of the same nature as the spicules Fic. 4. of the ectoplasm found in several of the Lobosa | Mastigella vitrea, Gold- (Trichosphaerium, etc.) and some of the Heliozoa schmidt. One of the Rhizo- mastigoda. Active form. (Heterophrys) (cf. pp. 23, 68). c.v, contractile vacuole ; f, portions of filamentous algae ingested as food ; fl, The life-history of Mastigella vitrina has soGisnidey (Attr recently been fully investigated by Gold- schmidt (4). During the vegetative life of this animal a series of binary fissions occur which are preceded by a withdrawal of the pseudopodia and flagellum and a mitotic 1 / j THE MASTIGOPHORA 165 division of the nucleus. The number of chromosomes seen in these mitotic divisions is about 40, and there are no centrosomata at the poles of the spindle. The sexual reproduction is preceded by the formation of mega- and microgametocytes. In the early stages the gametocytes cannot be distinguished from the ordinary vegetative individuals except as regards the microscopic character of the nuclei. A number of minute granules of chromatin (chromidia or sporetia of Goldschmidt) are extruded from the nucleus, increase in number and size, and give rise to the nuclei of the numerous gametes. The cytoplasm of the gametes is formed by a differentiation of clear protoplasm around each nucleus. In the case of the formation of the megagametes at least one mitotic division of the nucleus occurs, which has been inter- preted to be a polar division. A similar polar division of the nucleus probably takes place also in the formation of the micro- gametes, The elements of these nuclei are so small that it has not been proved that a definite reduction in the number of the chromosomes occurs. In both kinds of gametocytes an encystment accompanied by withdrawal of the pseudopodia and flagella occurs, but the microgametocyte encysts sooner than the megagametocyte. The gametes escape from the gametocytes and conjugate to form a zygote. The megagametes are about 3-6 » in diameter and are provided with a single flagellum 15-18 » in length. The micro- gametes are 2-8 » in diameter and are also provided with a flagellum. The zygote is a minute active monad, which divides several times by simple fission and then grows and assumes the general characters of the genus. The principal genera are :—Amoeboid and monomastigote: Mastiga- moeba, Schulze ; Mastigella, Frenzel ; Mastigina, Frenzel. Amoeboid and dimastigote : Cercobodo, Kent = Dimastigamoeba, Blochmann, and some of the species attributed to the genus Cercomonas (Fig. 5 (32, 33)). Heliozooid and monomastigote: Actinomonas, Kent. Heliozooid and dimastigote : Dimorpha, Gruber. TRIBE 2. PROTOMASTIGINA (sensu stricto). Solid food is ingested at a fixed point near the base of the flagellum. Sus-TrisE 1. Monomasticopa.! 1 The German term is ‘‘ Geisselspalte.” It is not a true pharyngeal pit although it strongly resembles one, 188 THE MASTIGOPHORA Other genera of Dinophysidae are Phalacroma, St. ; Dinophysis, Ehrb. ; Histioneis, St. (Fig. 10 (5, 6)), Crtharistes, St.; Triposolenia, Kofoid—San Diego region of the Pacific. SusB-CLass V. CYSTOFLAGELLATA. There are only three genera in this sub-class, and of these Noctiluca has long been known as a widely distributed organism that is often. the principal cause of the phosphorescence of the surface of the sea. The other two genera are little known. Noctiluca possesses a sub-spherical body with bilateral symmetry, the median plane of symmetry being determined by an elongated groove on the ventral side called the peristome (Fig. 15 (5)), at the bottom of which is the mouth. The nutrition is holozoic, and the mouth leads directly into the central part of the protoplasm, from whence trabeculae, exhibiting in life a streaming of the granules, radiate outwards towards the periphery. In certain regions the trabeculae are concentrated in the form of dense groups of fibrillae giving rise to a fibrillar plexus. One such plexus arises from the posterior end (f) of the central protoplasm, and is inserted along a thickened linear area of the integument behind the peristome called the bacillary organ, ‘ Staborgan” (Fig. 15 (5, c)). The integument consists of a resistent ectoplasm, a dense reticulate layer of alveolar protoplasm. The striated proboscis- like tentacle which arises in the middle line at the anterior end of the peristome, and constitutes one of the most notable features of its organisation, has a length equal to half the diameter of the sphere. It is a flattened contractile organ, convex on its outer side and concave on the inner adoral side. The protoplasmic trabeculae which traverse the tentacle are so disposed as to produce a striated structure comparable to that of striped muscle-fibres. Other peristomial organs are the dentiform process; the flagellum, which is borne upon or near a protuberance termed the lip; and lastly the mouth. The tooth! and the lip are placed asymmetri- cally upon the right wall of the peristome. The mouth occupies the posterior two-thirds of the fundus of the peristome, which is deepest behind and becomes progressively shallower in front. In front of the mouth, that is to say, in the anterior third of the peristome, are the lips, with the flagellum, the tooth, and the tentacle. The flagellum lies well within the peristome and requires practised observation for its discovery.? It resembles the typical flagellum of Mastigophora, namely, a filament of uniform thickness from base to apex. The tentacle can be extruded far beyond the confines of the peristome, but it can also be retracted, rolled up, and so escape superficial observation. ‘ The tooth is a protoplasmic organ. * It was discovered by Krohn in 1852, THE MASTIGOPHORA 189 The nucleus is lodged within the’ central protoplasm, and presents during life a transparent, homogeneous appearance. The ingested food is enclosed in food-vacuoles, which are some- times so large as to occupy the greater portion of the body. No contractile vacuole has been observed. The products of metabolism consist of albuminoid and fatty granules. Neither the slow contractions of the tentacle nor the rapid vibrations of the cilium are sufficient to impart movements of pro- gression to the inert body of Noctiluca, which merely drifts with the rest of the plankton, kept afloat by its own buoyancy. The Fie; 13: Sporulation by blastogenesis in Noctiluca miliaris, Sur. Fia. 1. “ Undulina ranarum,” Lankester, 1871. In B the nucleus is shown. The most general method of reproduction is by binary, longi- tudinal fission ; but multiple division or segmentation is also met with. As regards the life-cycle of the parasites, only little is as yet known in most cases. From the results of the most recent researches, however, it certainly appears probable that, apart from various blood-sucking Invertebrates which may (mechanically) transmit a given parasite, there is, in general, a true alternate host for each form; one, that is, in which definite phases of the life- cycle —including, most likely, sexual conjugation—are normally undergone. Further knowledge on this subject is greatly needed. Historical.—The first observation of a Trypanosome is probably to be ascribed to Valentin, who, in 1841, announced his discovery ! This flagellum is also termed the gubernaculum (see p. 159). THE HAEMOFLAGELLATES 195 of Amoeba-like parasites in the blood of a trout. In the two or three years following, Remak, Berg, and others recorded the occurrence of Haematozoa which were undoubtedly Trypanosomes in different fishes. The parasite of frogs was first seen by Gluge (1842), and in July 1843 Mayer described and figured certain corkscrew-like and amoeboid organisms from the blood of the same animal, which he termed variously Amoeba rotatoria and Paramoecium costatum or loricatum. A few months later (November) Gruby also published (24) an account of this parasite, to which he gave the new generic name of Zrypanosoma. 'The same form was subsequently described and figured by Lankester (30) in 1871, who, unaware of Gruby’s work, called it Undulina ranarum; this author was the first to indicate the presence of a nucleus in the organism (Fig. 1, B). The well-known parasite of rats was discovered by Lewis, in India, in 1878, and was afterwards named Herpetomonas lewisi by Kent.! It is to Mitrophanow (1883 to 1884) and Danilewsky (1885 to 1889), however, that we owe the first serious attempts to study the com- parative anatomy of these Haematozoa. The work of the latter researcher in par- ticular is deserving of recog- nition, especially when the primitive state of knowledge in regard to blood-technique in those days is borne in mind. Some of Danilewsky’s figures of a Trypanosome of birds are reproduced in Fig. 2. Trypanosomes were first met with in cases of disease by Griffith Evans, who, in 1880, found them in the blood of horses suffering from Surra in India. The organisms were thought by him to be Spirilla. Steel rediscovered the same ae A-C, different forms of Trypanosoma sanguinis form a few years later and avium, Danilewsky. D, the same parasite dividing aS . . longitudinally. n, nucleus ; vu.m, undulating mem- took a similar view of its brane ; J, flagellum. (After Danilewsky.) ‘ affinities, naming it Spirochaeta evanst. In 1894 Bruce found the celebrated South African parasite (7. brucit) in the blood of cattle and horses laid low with Nagana, or Tsetse-fly disease ; and this worker subsequently demonstrated, in a brilliant manner, the essential part played by the fly in trans- mitting the parasite. Bruce’s discovery may be said to have jnaugurated a rapid increase in the number of known forms, the Fie, 2. 1 This form is now placed in the genus 7rypanosoma. 196 THE HAEMOFLAGELLATES knowledge of which has in many cases thrown light upon the etiology of maladies previously obscure. Thus, two characteristic diseases, Dourine, which afflicts horses and mules in Northern Africa and the Mediterranean littoral, and Mal de Caderas of horses in South America, were next shown to be caused by different Trypanosomes; and since then many other varieties of trypanosomosis have been described, chiefly from Africa, the home of the dreaded Tsetse-fly. Prominent among them, unfortunately, is human trypanosomosis. The credit for first recognising a Trypanosome in human blood, and describing it as such, must undoubtedly be assigned to Nepveu (1898). The parasites were not definitely associated with disease, however, till 1901, when they were seen in the blood of a European in Senegambia suffering from intermittent fever. Forde first found the organisms, but was uncertain of their nature ; he showed them to Dutton, who recognised them as Trypanosomes, and gave this form the name of Yrypanosoma gambiense. A _ year later (1902) Castellani discovered what has been shown to be the same parasite in the cerebro-spinal fluid of patients suffering from sleeping-sickness in Uganda, and it has since been conclusively proved by Bruce and Nabarro that this organism is the true cause of that terrible disease. More important, however, from the standpoint of Protozoology, than these interesting medical discoveries have been the investigations by Brumpt, Laveran and Mesnil, Léger, Minchin, Schaudinn, the Sergents, and others during the last few years upon numerous other, mostly ‘‘ tolerated” forms ; to their researches, indeed, we owe most of our knowledge at the present time, relating to the life-cycle of the Haemoflagellates. And it is fitting, here, to pay a tribute to the value of the characteristic stain first made known by Roman- owsky, and its subsequent modifications (eg. those of Giemsa, Laveran, Leishman, etc.), without which, it is safe to say, this progress would have been impossible. 2. OCCURRENCE AND TRANSMISSION ; HABITAT AND EFFECTS ON Host. (a) Occurrence and Transmission. Trypanosomes are harboured by members of all the chief classes of Vertebrates, with the exception of Cyclostomes. Mammals, birds, and fishes furnish, however, by far the greater number of hosts. Fewer parasites have been described from Amphibia, and up till now only from frogs ; while, among Reptiles, their occurrence has only been observed in two or three instances. Data with regard to the frequency with which individual species are to be met with, in any THE HAEMOFLAGELLATES 197 particular kind of host, are as yet somewhat scanty. In one or two cases, however, the parasites are known to be fairly common. Trypanosoma lewisi, for example, occurs in a considerable percentage of sewer-rats throughout the world, having accompanied these rodents in their ubiquitous migrations; the proportion of hosts infected varies usually from 10 to 40 per cent. In considering the occurrence of Trypanosomes in Mammals careful distinction must be drawn between true or natural hosts and strange or casual ones. In the former case, by reason of the long-existing association between host and parasite, a condition of mutual toleration has been reached, which, in ordinary circum- stances, enables a proper balance to be maintained on both sides. On the other hand, when a Trypanosome gains an entry into animals which have never been previously liable, by their dis- tribution, to its invasion, and which are consequently unaccustomed and unadapted to the organism, it usually produces markedly harmful effects. Such a state of affairs has resulted, for example, from the march of civilisation into the “hinterlands” of the various Colonies, where man, together with the numerous domestic animals which accompany him, has been brought into proximity to big game, etc., and what is equally important, into the zone of the blood-sucking insects which prey upon the same. Very many of the common domestic Mammals can be success- fully infected (either in an accidental way or else artificially) with different “pathogenic” Trypanosomes, to which they succumb more or less readily ; they cannot be regarded, however, as natural hosts of those Trypanosomes. In considering disease-causing forms, the more narrowly the original source of the parasite concerned is defined, the closer do we get to the true Vertebrate host or hosts. In the case of the Nagana parasite, it has been shown that such are almost certainly to be found among buffaloes and various Antilo- pidae (eg. the gnu, “ koodoo,” etc.), while, again, the native host of T. equinum, of Mal de Caderas in South America, is most probably the capybara. It may be said undoubtedly, with regard to the many lethal Trypanosomes now known, that there is, in each case, some indigenous wild animal tolerant of that particular form, which serves as a latent source of supply to strange Mammals coming into the vicinity. Transmission.—In the transmission of the parasites from one Vertebrate individual to another, a blood-sucking Invertebrate is almost invariably concerned.! In the case of all Trypanosomes of 1 Trypanosoma equiperdum, the cause of Dourine or horse-syphilis, is conveyed by the act of coitus ; and it is quite uncertain whether this parasite is ever transmitted naturally by an insect. Moreover, Koch has recently brought forward evidence (29, Schluss- Bericht) which, he thinks, tends to show that the human parasite (7. gambiense) can also be transmitted by sexual intercourse. 198 THE HAEMOFLAGELLATES warm-blooded Vertebrates for which the transmitting agent is known, this is an insect, generally a member of the Diptera; in that of Trypanosomes of cold-blooded Vertebrates the same réle is usually played by an Ichthyobdellid leech (Piscine forms), but possibly now and again by an Jzodes (some Amphibian or Reptilian forms). The actual relation between the parasite and the transmitting Invertebrate has long been questioned, and there are still some. very important instances in which the real state of affairs is not certain. But it would seem, from the results of recent work, that in most cases some Invertebrate or other acts as a true alternate host. Thus, so far as leeches are concerned in connec- tion with the Trypanosomes of fishes, the investigations of Léger (50), Brumpt (10-12), and Keysselitz (27) have made it clear that the parasites not only live quite normally, but undergo a definite evolution in particular organs of leeches which have fed on infected fish. Frequently this further development can only proceed, at least to its full extent, in a certain leech to the exclusion of others (e.g. in a Hemiclepsis and not in a Piscicola, or vice versa) ; this restric- tion points distinctly to the leech in question being a specific natural host. Again, according to the celebrated researches of Schaudinn (75) on an Avian Trypanosome, Trypanomorpha (Trypanosoma) noctuae, a species of gnat (Culex) provides the alternate host, in which a complex part of the life-cycle takes place. It is interesting to note that, as might be expected, there is a regular periodicity in the infectivity of the gnat; that is, it can only transmit the infection after such and such an interval has elapsed since the meal when it became itself infected. Coming, lastly, to the Mammalian forms, Prowazek (68) has described phases of development of 7. Jewisi in the rat-louse (Haematopinus sp.), and considers that this insect serves as a true Invertebrate host ; though he was not able to prove the actual transmission of the parasites back to the rat by means of it." Interest and discussion has mostly centred, however, upon the part played by the transmitters of the lethal Trypanosomes, and it is only quite recently that any light can be said to have been thrown upon the subject. It has for some time been generally recognised that, in many cases at any rate, a particular biting-fly is chiefly responsible for the spread of a particular parasite in an infective district. In such cases, a striking coincidence usually exists between the area over which a certain trypanoso- mosis is prevalent and the zone of distribution of a certain fly, Thus, of two well-known African Trypanosomes, one, 7’, bruci?, the cause of Nagana 1 This has been effected, however, by earlier observers (Rabinowitsch and Kempner) by means of fleas, which are possibly the “right” insects. a ee ee eee ee THE HAEMOFLAGELLATES 199 or Tsetse-fly disease in South-East Africa, is conveyed by Glossina morsitans * (Fig. 3, A and 8B), while the other, 7’. gambiense, the cause of sleeping- sickness, has for its carrier in Uganda another Tsetse-fly, G. palpalis. Working upon this knowledge, many investigators have at one time or another performed series of experiments with a view to finding out whether any developmental cycle is undergone by the parasites while in the fly, and whether definite periods of infectivity occur, on the analogy of the malarial parasites in mosquitoes. The earlier results obtained seemed to indicate that the rdle of the fly was purely mechanical—the insect acting merely like an artificial inoculating tube. Bruce, in the course of his pioneer work in Zululand, found that the flies could, with Fic. 3. Various blood-sucking flies. A and B, Glossina morsitans (transmits Trypanosoma brucir, of Nagana), x 2; C, Hippobosca ru fipes (thought to transmit 7’. theileri, the cause of ‘ bile-sick- ness”), X 13; D, Tabanus lineola (probably conveys the Surra parasite, T. evansi), X 14; HB, Stomorys calcitrans (suspected in connection with 7. equinwm, of Mal de Caderas), x 23. (A and B from Lay. and Mesn., after Bruce; C after L. and M.; D and E after Salmon and Stiles.) varying success, infect a healthy animal if allowed to bite it up to forty- eight hours after being themselves fed on an infected one, but not after- wards. Similarly, Bruce, Nabarro, and Greig (8) ascertained that G. palpalis could give rise to an infection eight, twenty-four, or forty-eight hours after feeding, but after two days they could no longer obtain a successful inoculation. Moreover, some experiments extended over two months gave no sign of any periodicity of infection. Nevertheless, these workers found that the Trypanosomes could at all events live and retain their mobility in the stomach of the fly up to seventy-one hours. Similar results were obtained by Minchin, Gray, and Tulloch. In their interesting report (59) these authors state that they could find no evidence of a fly becoming infectious at any particular period after 1 This parasite is also conveyed, in different districts, by G. pallidipes and G. fusca. 200 THE HAEMOFLAGELLA TES being fed, experiments being carried out up to an interval of twenty-two days. An additional and significant fact remarked upon by them is that only the first animal which the experimental fly was allowed to stab became infected ; if the insect was removed before its meal was completed and immediately placed on another animal, this latter did not become infected. That is to say, after a fly had been allowed to, as it were, clean its proboscis from the Trypanosomes remaining in it since its previous meal (on an infected animal), it was no longer infectious. These facts make it certain that Trypanosomes can be and are conveyed by Tsetse-flies in a purely direct and mechanical manner ; and so far as 7. gambiense and sleeping-sickness in Uganda are concerned, it is probable that their spread, through the agency of G. palpalis, has been largely if not entirely in this way. But this does not by any means end the matter. Minchin, Gray, and Tulloch bring forward observations which point to a commencing cycle of development of 7. gamliense* in the fly. Up to forty-eight hours the Trypanosomes present in the stomach of an infected fly are markedly differentiated into two types, which probably represent sexual forms. After forty-eight hours a type of more indifferent character makes its appearance, which usually becomes scanty with lapse of time, till at ninety-six hours scarcely a Trypanosome can be found. It is interesting to note that during this interval the parasites steadily increase in size. Coming next to Koch’s recent investigations on behalf of the German Sleeping-Sickness Commission, a very important observation is recorded (29). ~ psa ee ales f ee 4 the indifferent type, pro- ay ey; duced by rapid multiplication a oP in the hinder part of the intestine. d. It is this Herpetomonad pee type which undergoes en- Encystment of the narrow, Herpetomonad form ey stment. In = st-formation of Trypanosoma grayi. (After Minchin.) the flagellum becomes shortened and at the same time apparently thickened. The cyst begins to appear as a layer of substance, probably of a slimy or mucoid nature (cf. Prowazek’s ‘““Schleimeysten” in the case of Herpetomonas muscae-domesticae [69]), which forms a cap at the aflagellar end (Fig. 22, )). These two processes continue until, on the one hand, the flagellum is completely retracted, and, on the other hand, the body is enveloped in a pear-shaped cyst (c), which is at first incomplete at the pointed end. ‘The flagellum appears next to become retracted into a pink- staining vacuole (cf. the opposite process in the formation of the flagellar phase of Leishmania (Piroplasma) donovani); finally, the flagellar vacuole fades away, the cyst meanwhile closing up. Eventually there results an oval or circular cyst, containing hyaline cytoplasm and the two chief nuclear masses (¢). In this guise, THE HAEMOFLAGELLATES 233 presumably, 7. grayi passes into the outer world, to be swallowed subsequently by its alternate host.! Comparing 7. grayi with 7. brucii, an essential point of contrast is at once noticed. In the first-named, the small, Herpetomonad forms, which have the function of propagating the infection to a fresh host, occur mainly in the proctodaeum and leave the fly per anum. In the latter, on the contrary, the small, Crithidial forms, which are compared by Minchin with those of 7’. grayi just men- tioned, were found almost exclusively in the proboscis ; moreover, no Trypanosomes of any kind were seen in the hindermost part of the gut (proctodaeum). Hence the propagation of 7. brucii would appear to be just as certainly by the inoculative method as that of T’. grayi is by the contaminative one. Further, just as there is at present no evidence of contaminative infection in 7. bruciz, so there is none of inoculative infection in 7. grayi; for although Minchin says that the slender type, which he also thinks is a propagative form, was met with farther forward than the Herpetomonad type, it was not met with farther forward than the stomach. And this is as far as our knowledge goes up to the present. Schaudinn’s Work on Haematozoa of the Little Oul. There remains for consideration the remarkable research of the late Fritz Schaudinn on certain parasites of Athene noctua and Culex pipiens, namely, Trypanomorpha (Trypanosoma) noctuae and “ Try- panosoma” (Leucocytozoon, Spirochaeta) ziemanni. Exigencies of space preclude a detailed account of this work, only the main outlines of which can be given here, but a full description will be found in the writer’s article on the Haemoflagellates (3). Taking first Zrypanomorpha noctuae, the life-cycle may be con- veniently commenced with the motile copula or ookinete resulting from conjugation in the stomach of the gnat. While the nuclear fusion of the two sets of elements (kinetic and trophic) derived from the original gametes is being completed, leading to a single, large, compound nucleus, the ookinete is getting rid of unnecessary material, such as the pigment-grains and reduction-nuclei left over in the cytoplasm (Fig. 10, A, B). Even in the ookinete stage, Schaudinn recognises the three types of individual, indifferent, male, and female, distinguishable by differences in the size of the nuclei relative to the cytoplasm, and by the varying appear- ance of the latter. The development of an indifferent Trypanosome has been de- scribed above (p. 213). When formed, a period of active movement and multiplication sets in, succeeded later by a resting condition. The 1 The reasons for considering that this parasite is not merely a “ fly-parasite”’ have been given on p. 201. 234 THE HAEMOFLAGELLATES parasites now become gregariniform, and strongly recall the similar. phase described by Léger (48, 51) in certain Herpetomonads. The Trypanosome bores into an epithelial cell of the stomach by means of its flagellum, which is reduced to a short, rod-like organella. Binary fission may go on, often leading to the formation of a dense layer of attached parasites. On the parasites again becoming try- paniform, the flagellar apparatus is reconstituted by the kineto- nucleus. This alternation of resting and active periods is limited- Eventually the indifferent Trypanosomes may pass into the blood Fic. 23. Development of microgametocyte and male Trypanosomes from an ookinete of male character. (After Schaudinn.) m.n, male nuclei; fin, degenerating female nucleus; m.t, male tropho- nucleus ; m.k, male kinetonucleus ; M.7, male Trypanosome ; r.b, residual body. of the owl; or they may apparently become sexual forms, male or female ; or else, during a period of hunger, they die off. In the development of an ookinete of male character, or micro- gametocyte, there is an early separation of the nuclear constituents into two halves, male and female. The female portion consists of a large, loose nucleus (Fig. 23, C and b, f.n), which gradually degenerates and disappears. ‘The male portion, on the other hand, gives rise to eight little double-nuclei (C and D, m.n), each consisting of trophic and kinetic portions. ‘The microgametocyte now becomes rounded, the eight double-nuclei take up a peripheral position (£), and the cytoplasm opposite each grows out as a little prominence. As THE HAEMOFLAGELLATES 235 these elongate, each accompanied by a double-nucleus, they take on a trypaniform appearance, which is completed by the development of a flagellum. Finally, the eight little male Trypanosomes (F, ™.7), which are homologous with microgametes, break away from the central residuum. These forms are apparently incapable of further development in any way and soon die off. Schaudinn accounts for this by the condition of the trophonucleus, which, he says, has undergone reduction. The early stages in the formation of a female Trypanosome are similar to those in the case of a microgametocyte. Here, however, it is the eight small double- nuclei, representing the male constituents, which degenerate, leaving the large female nucleus to become differentiated and give rise to the locomotor apparatus in the same way as in an indifferent form (Big. 24,°-0).. In the females the flagellum, etc., is poorly developed, and the movements of the para- sites are slow and feeble. These Trypanosomes seem unable to divide. They grow to a large size, and store up a_ considerable amount of reserve-nutri- : Development of a female Trypanosome from an ment in the cy toplasm. ookinete of female character. (After Schaudinn.) These forms are the most ™.”, degenerating male nuclei ; a.sp, first axial spindle ; i of female nucleus; fit, female trophonucleus; f.k, resistant to external in- female kinetonucleus, fluences, and can survive long hunger-periods, in a gregariniform, resting condition. With the advent of fresh blood into the stomach of the gnat, the female forms undergo a process of parthenogenesis, consisting of nuclear reduction and a kind of self-fertilisation. ‘Thus rejuvenated, they are able to give rise to a fresh succession of Trypanosomes of all three types. The Behaviour and Development of the Trypanosomes in the blood of the Owl.—All the Trypanosomes met with in the bird can be recog- nised as belonging to one of the three categories observed in the gnat. On entering the blood, the small indifferent forms at once Fic. 24. 1 According to Schaudinn, these gregariniform females can bring about hereditary infection, remaining dormant in the ovaries until the eggs are laid and the larvae develop. 236 THE HAEMOFLAGELLATES attach themselves to the red blood-corpuscles (Fig. 25, A and B), and begin a period of rest and growth. The locomotor apparatus disappears and the two nuclei come close together. The form of the parasite is now quite that of a young Halteridium, a well-known malarial parasite of birds, and, moreover, in twenty-four hours the first pigment-grains appear in the cytoplasm (c). By this time the parasite has greatly increased in size. It becomes vermiform and active, reconstitutes its flagellum, etc., and leaves the host-cell (p), usually in the night-time, becoming once more a typical Zrypano- morpha (£). This alternation of attachment and growth with active movement in the plasma is repeated for six days, until the full size of the parasite is attained (F and G). The adult Trypanosome then undergoes successive longitudinal divisions, until the resulting daughter-individuals have reached a minimum size, when they repeat the whole cycle. It is worth noting that Schaudinn never Fic. 25. Stages in the growth of an indifferent Trypanosome in the blood of the owl. , nucleus of red blood-corpuscle ; p, young ectocorpuscular parasite. (After Schaudinn.) observed any multiplication of the parasites in the gregariniform (Halteridium) condition, by schizogony, such as is met with in other Haemosporidia. Microgametocytes (male forms) arise from very young indifferent Trypanosomes. Each gives rise to eight small, slender micro- gametes, in the same way as do the corresponding forms in the gnat. The microgametes are very specialised organisms. The trophonucleus (in a reduced condition) forms a long thread, on which four chromosomes are strung at intervals. There is no free flagellum at the anterior end, but the body has a whip-like tail posteriorly. The full-grown megagametocytes are large female Trypano- somes, which are no longer able to assume the trypaniform con- dition, but remain enclosed by the pallid and disorganised host-cell which they were last able to penetrate. In other words, they are identical with the female gametocytes of Hualteridium. Maturation f 4 THE HAEMOFLAGELLATES 237 and fertilisation do not take place until the sexual forms are trans- ferred to the gnat. The process in its main outlines has been previously described by MacCallum in another species of [alteridiwm.! Schaudinn adds that, as soon as the parasites leave the warm- blooded host, the megagametocytes become rounded off, rupture the delicate envelope still surrounding them, and then undergo a series of reduction-divisions, after which they are ready to be fertilised. The zygote develops into one of the three kinds of ookinete with which this description began. Leucocytozoon (“ Trypanosoma”) ziemanni.—Even more surprising are the data put forward by Schaudinn in the case of the other para- site (or set of parasites) upon which he worked. Just as a species of Halteridium is regarded as ontogenetically related to 7rypanomorpha noctuae, so Leucocytozoon ziemanni, a parasite of the white corpuscles and erythroblasts, is said to be intimately connected with what has been hitherto taken for a species of the genus Spirochaeta, a well- known bacterial type. Far from being, however, a true member of the Bacteria, this species at any rate was regarded by Schaudinn as possessing all the fundamental characteristics of a Trypanosome (see Fig. 7, H). The plan of the life-cycle is fundamentally similar to that just summarised, the same sets of forms being described. Two or three distinguishing features may be noticed. The indifferent Trypanosomes are extremely spirochaetiform (Fig. 26, A—D) ; after longitudinal fission, the two daughter-individuals remain attached end-to-end (B and C), the resemblance to a Spirochaete being thereby accentuated.? The resting-phases, little pear-shaped forms with two nuclear elements A-D, formation and fission of spirochaeti- P form ‘‘ couples” in ‘‘ Trypanosoma” (Spirochaeta) (E and F), are very Piroplasma- ziemanni; E, F, resting-phases of same; G, 4 agglomerated cluster of very minute forms. like and strongly recall the (After Schaudinn.) Leishman-Donovan bodies. On the other hand, the gametocytes (in the blood of the owl) are very large and broad, and distinctly trypaniform, even possessing Fia. 26. 1 See the account of the Sporozoa, by Minchin, in this treatise (Vol. I. Part II.). 2 According to Novy, M‘Neal and Torrey (64), Topfer has recently cultivated a true Spirochaete (7.e. a Bacterium) from the owl, which possesses also minute resting- forms. Hence Schaudinn’s spirochaetiform “ Trypanosoma”? may have been really this same Spirochaeta. 238 THE HAEMOFLAGELLATES well-marked myonemes. Prior to gamete-formation, both gametocytes come into relation with the leucocytes, in an unusual manner (see under ‘‘ Habitat,” p. 205), and lose all trace of locomotor organellae. Microgamete-formation, maturation and fertilisation of the megagamete (Fig. 27), in the gnat, present nothing unusual. Instead of an _ ookinete giving rise to a single Trypanosome, as in Trypanomorpha, it grows con- siderably, forming a large coil, and nuclear multiplication goes on actively at the same time (Fig. 28). Ulti- mately, an enormous number of little spirochaetiform parasites are pro- duced, which populate the alimentary Fertilisation of a megagamete bya a microgamete. The trophic and kinetic canal of the gnat. Baa rene agi ctchedet: Criticism of this remarkable work lee i tltadtd eg 1 based mainly upon the realisation ter me Rees right. (After that, In such a complicated study, there was a grave source of possible error, and there is nothing to show that this was eliminated. The opinion has been very generally expressed that Schaudinn did not sufficiently guard against the liability of confusing and mixing up the life-histories of entirely distinct parasites. In Fie. 27. Fia. 28. Growth and metamorphosis of an indifferent ookinete ; in C nuclear multiplication is well advanced, (After Schaudinn.) the first place, it is said that in the species of owl used at least four separate Haematozoa occurred: two free parasites, namely, a Trypanosome and a Spirochaete (“ 7rypanosoma” ziemanni) ; and two intracellular ones, a LHalteridium and a Leucocytozoon. It may be at once admitted that this is quite possible. At any rate, the entire subject is reopened and cannot be settled definitely until | . THE HAEMOFLAGELLATES 239 the life-cycle of some or of all the parasites concerned has been reinvestigated. (See Note below.) While preserving an open mind upon the matter, the writer would point out that, if no indubitable confirmation of Schaudinn’s far-reaching conclusions can be said to have been furnished, the merely negative evidence adduced by Novy and his colleagues is by no means sufficient proof of their erroneousness. Because the injection of cultures of certain Trypanosomes in artificial media, into birds, was not followed by the appearance of Cytozoa in the blood, these workers apparently conclude (/.c.) that there is no connection whatever between these two groups of Haematozoa. And this com- prehensive generalisation is put forward, although in nearly all cases they failed to obtain even a Trypanosome-infection by this means, apart altogether from the question whether the particular form with which they did once succeed had itself an intracellular phase ! We will admit that the cultivation-method, which is of undoubted use in other ways, may not be without value in studying the life- history. In certain cases, for example, the behaviour of the parasites on their arrival in the culture-medium may to some extent indicate or suggest what happens when they pass into the Invertebrate host, because of the general similarity of the physical conditions, etc., to which they are at first subjected. An illustration of this is afforded by the development of the Flagellate phases of the Leishman-Donovan bodies in cultures. Nevertheless, we certainly think that the value (in this respect) of the cultural method of re- search is limited, and that great caution is necessary in drawing:infer- ences as to a parasite’s life-history from the results obtained by it. We dissent entirely from the American authors when they maintain that the culture-medium is, for all practical purposes, the equivalent Note.—The present writer has always been reluctant to think Schaudinn made such a series of mistakes, It has always seemed to him that this author’s celebrated work on the Coccidia of Lithobius has not been taken into account sufficiently by those who have maintained that he was hopelessly wrong in the case of the parasites of the Little Owl. It is with the greatest pleasure, therefore, that on the point of publication of this article, the writer is able to add that after a most arduous investigation on the Haematozoa of the common chaffinch (Fringilla coelebs), he has at length obtained the first definite and unmistakable evidence, of which he is aware, in favour of one of Schaudinn’s conclusions. Here, there is only room to say that, as a result of his observations, he has now little doubt that a Halteridium parasitic in the chaffinch becomes actually, in certain phases, a little Trypanosome; in other words, that the Haltertdiwm and the Try- panosome which occur in this bird are ontogenetically connected (vide Q.J. Mier. Sci. iii. p. 339, Feb. 1909). Hence the writer feels reassured with regard to the truth of the corresponding part of Schaudinn’s work. 240 THE HAEMOFLAGELLATES of the medium in the Insectan host; on the contrary, we consider that the former, whatever indications it may furnish, cannot replace altogether the latter. It seems to us that Novy and M‘Neal entirely fail to appreciate the intimate and specific relations of Protozoan parasites to their hosts, and the remarkable degree to which their biology is adapted to the same. The Sporozoa in their entirety illustrate this, so do other parasitic Protozoa, and there is no reason to suppose the Haemo- flagellates are different. We agree fully with Brumpt that the chemical and physiological medium of a particular Invertebrate is essential for the adequate development of all such phases of the life-history of a Trypanosome as may be undergone outside the Vertebrate host. And the various researches above summarised, which go to show that there are right and wrong hosts for the parasites, and that only certain “ripe” phases, the outcome of the sojourn in the right host, can reinfect the Vertebrate host success- fully, afford strong support to this view. Another criticism put forward by Novy and M‘Neal and others is that the Flagellate phases found in the mosquitoes (Culex), which Schaudinn regarded as belonging to Zrypanomorpha of the Little Owl, were in all likelihood purely Insectan parasites, of a Herpeto- monad or Crithidial type, which had nothing to do with the blood forms. Before discussing this view it is necessary to consider briefly the subject of these Insectan Flagellates, one which is also of very great importance because of its bearing upon the phylogeny and derivation of the Trypanosomes. 7. THE INSECTAN FLAGELLATES: THE EVOLUTION AND PHYLOGENY OF TRYPANOSOMES. (a) The Insectan Flagellates. Several of the earlier workers have commented upon the occur- rence of Flagellates in mosquitoes. Thus in 1898 Ross observed parasites which he has recently (74) compared with Léger’s genus Crithidia in Anopheles, larva, pupa, and imago. A similar parasite was found by Christophers in 1901, occurring in swarms in Anopheles and Culex. Durham, again, the year before, had noticed numerous “ Trypanosomes ” in a Stegomyia which had fed upon a bat. The first serious contributions, however, to our know- ledge of the Flagellates parasitic in Insects are Léger’s researches (47, 48, 51, 52), 1902-1904, on certain Herpetomonadine forms. Besides the genus Serpetomonas, Léger has distinguished another type of form, which he has termed Crithidia. Both types show, in general, an alternation of monadine (flagellate) phases with gregariniform (resting, non-flagellate) ones. In the latter condition, the parasites occur as small, rounded, pear-shaped, or ‘he. wee ns chen alpdastonaal mah OX THE HAEMOFLAGELLATES 241 even oblong bodies, attached, often in great numbers, to the epithelial cells. The flagellum is either absent or reduced to a short rostrum, serving for attachment (Fig. 29, D and G). The two nuclei (tropho- and kinetonucleus) lie close together, usually near the base of the cell. In this phase, the general resemblance to the Leishman-Donovan bodies may be quite marked. The distinction between the two generic types is based upon the form and size of the monadine phase. In Herpetomonas the body is very elongated and slender, often acicular, the posterior end usually Fig. 29. A, C, Herpetomonas (Crithidia) minuta ; D, attached (gregariniform) phases of same; B, H. gracilis, Léger; BE, F, H. subulata, Léger; G, attached phases of same. (After Léger.) x 1800. tapering away finely (Fig. 29, Band £). In Crithidia, on the other hand, it is much shorter and wider, of a pyriform shape ; the hinder end is never drawn out, but terminates bluntly in a rounded or an obtuse manner. The parasite Herpetomonas (Crithidia) minuta, Léger, appears to be intermediate, however, between these two types, some individuals approximating to a Herpetomonad form (A), others to a Crithidial one (Fig. 29, c). As a matter of fact, the classificatory distinctions between these various Insectan Flagellates cannot be regarded as at all settled. In many forms of Herpetomonas (e.g. H. muscae-domesticae,! H. jaculum, or H. gracilis (B)), the kinetonucleus is situated near the 1 H. muscae-domesticae is included here as a typical uniflagellate Herpetomonad. Prowazek (69) described this form as possessing a pair of flagella, parallel to and connected with one another ; he considered this parasite to be a bipolar type (on the lines of Schaudinn’s “ Urhaemoflagellate”’) in which the body has been bent up so that the two ends have come together and united, the flagella alone remaining distinct. Léger observed no signs of two flagella in non-dividing individuals, either of this species or others ; and the same is true of the describers of the numerous other Herpetomonads. 16 242 THE HAEMOFLAGELLATES anterior end ; the flagellum is not attached to the side of the body at all but straightway becomes free, and there is no sign of an undulat- ing membrane. ‘These forms are mostly parasitic in Invertebrates - which do not suck blood. In H. subulata, however, which is parasitic in the digestive-tube of Zabanus and Haematopota, predatory on cattle and horses, the kinetonucleus lies much farther from the anterior end, and may be almost opposite the trophonucleus (Fig. 29, F). The flagellum, which has been, as it were, drawn back with it, is in most individuals attached for the proximal part of its length to the anterior part of the body, by means of a delicate cytoplasmic border, which constitutes a rudimentary undulating membrane. Thus there is an approach to a trypaniform condition. Again, in the case of Crithidia fasciculata, found in the intestine of mosquitoes, Léger has described a very distinct undulating membrane, which gives the parasite, especially in the more elongated individuals, a very Trypanosome-like appearance. Novy and his colleagues have also studied C. fasciculata, as found in Culex; but while admitting the presence of a membrane, regard it as imperfect and only poorly developed. These authors describe, in addition, another Herpetomonadine type, H. (Z'rypanosoma) culicis, the long forms of which show clearly an undulating membrane. We are now in a position to discuss the relation (if any) of these Flagellates to the Trypanosomes of Vertebrates. When first describing Crithidia, Léger expressed the opinion that this parasite was very likely only a stage in the development of a Haemoflagellate ; further, in his notes on H. subulata (52) he added the remark that the same was probably true of many of these Herpetomonad or Crithidial forms found in biting Insects, though this would not apply, of course, to those species occurring in non- biting Insects (such as Musca, Sarcophaga, etc.). Moreover, Schaudinn himself (/.c.) comments on the great similarity between (what he took to be) the phases of Zrypanomorpha noctuae in Culex and those of Léger’s Crithidia. Quite the opposite view is held by Novy and M‘Neal, who, after first (62) regarding the Flagellates found by Schaudinn in mosquitoes as being simply “cultural” forms, of no real significance in the life-history, in their later paper (63) consider it much more likely that the Insectan parasites are entirely distinct from the Trypanosomes in the blood. (They look upon the parasites found in leeches, however, as ‘‘ cultural” forms of Piscine Trypanosomes.) A similar opinion is expressed by Ross, who points out that he found Crithidia in the mosquitoes (larvae and pupae) before they fed on blood, and thinks the parasites were in the first place swallowed by the larvae. In a very interesting note Patton has recently (65) described ee THE HAEMOFLAGELLATES 243 stages in a LHerpetomonas of Culex pipiens, whose life-cycle would seem in some respects to conform to the scheme suggested by Ross. In its monadine, determinative form, the parasite appears to be a typical Herpetomonas, with no indications of an undulating membrane. All the phases observed, Patton states, exhibit great similarity with those of Piroplasma donovani (see pp. 256 et seq.). Here it may be pointed out that in the larvae the parasites resembled the Leishman- Donovan bodies as they occur in human tissues; in the nymphs, stages corresponding to the developmental forms of the Leishman- Donovan bodies (in cultures, or in the bed-bug), z.¢. pear-shaped forms with flagella, were numerous ; while in adult mosquitoes (mid- and hind-gut) there were fully developed Herpetomonad forms. Patton thinks these are passed out into the water, and in some guise or other ingested by the larvae, the cycle thus beginning again. (He has privately informed the writer that the parasites may encyst in the rectum, and be thus passed out to the exterior, to give rise to the small round forms in the larva.) Patton also notes the occurrence of a Herpetomonad, which has an obvious undulating membrane, and which possesses similar rounded aflagellar forms, in a water- bug. ‘The author concludes by regarding these two parasites as limited to their Insectan hosts. In endeavouring to draw some general conclusions from the above opposing ideas, we are, it seems to the writer, greatly helped by comparing what is known in the case of other groups of Trypano- somes. In the first place, as regards those met with in Tsetse-flies, some of which, at any rate, were formerly considered to be solely fly-parasites, there appears to be no escape from the conclusion that, on the contrary, all the forms are blood-parasites. In our opinion the utmost weight is to be attached to this conclusion. In addition, we have the Trypanosomes of leeches, which are generally agreed to belong to different Piscine forms. On these grounds alone, then, it appears justifiable to suppose that Avian Trypanosomes are to be found in mosquitoes, and not at all improbable that some at least of the phases so clearly described by Schaudinn from mosquitoes which had fed on infected owls, did indeed appertain to Zrypano- morpha noctuae. Again, to consider the subject from the Insectan standpoint, so far as the writer can see, Novy and his colleagues have by no means proved that their Flagellates in wild mosquitoes are not, in some cases at any rate, phases of Trypanosomes of birds (or other Vertebrates). For instance, the Trypanosoma (Herpetomonas) culicis described by these authors—with various forms of which they compare certain phases of Zrypanomorpha—is quite as probably a blood-parasite as a purely Insectan form ; indeed, the possibility of this being so is admitted by its describers. Moreover, they remark on the resemblance between the genera Herpetomonas, Crithidia, and 244 THE HAEMOFLAGELLATES Trypanosoma, especially when the “cultural” forms of the last-named are compared with those of the other two (or with what Novy and M‘Neal regard as their equivalents—the Insectan forms). In the case of the Trypanosomes, there is the same relative position of the two nuclei, either close together, or the kinetonucleus even on the flagellar side of the trophonucleus ; while certain of them show no sign of an undulating membrane, but have a typically Herpetomonad facies. Novy and M‘Neal, in fact, would include all these types in the genus Trypanosoma. Further, we may point out that according to the view which these authors themselves hold regarding the origin of the blood-. Trypanosomes, it is most natural to suppose that they are to be met with, quite at home, in an Insectan host. The American workers say that parasitism in the living blood is to be looked upon as the result of previous adaptation to the more or less digested blood (in the Invertebrate). (As will be seen later, we agree with this view, where certain Insects are the Invertebrate hosts.) Now, in this course of evolution of certain blood-Trypanosomes, it may be reasonably inferred that at one stage the parasites still remain connected with the Invertebrate after having gained a footing in the Vertebrate (say a bird). The question would seem to be, rather, which if any blood-forms so descended have lost the ability to live (and develop) in their Invertebrate host—a course which would probably greatly restrict their opportunities for dispersal. (In this connection the case of the Leishman-Donovan bodies is most instructive ; cf. pp. 258, 259.) Hence, summing up, there can be little doubt that certain of these parasites of mosquitoes, especially those with trypaniform characters, are connected with some Vertebrate host, just as are those of other blood-sucking Invertebrates. At the same time, it is also probable that some of the (typical) Herpetomonads found (e.g. those occurring in larvae, such as Patton’s form, also certain forms described by the Sergents) are simply and primarily parasites of the Insect. Lastly, it is, of course, possible that such a parasite may have developed a trypaniform condition as an adaptation to the food of a sanguivorous Insect, without, however, having become able to live in the Vertebrate host ; but so far no example of such a case is definitely known. And this brings us to the subject of the derivation of the Trypanosomes. (b) Evolution and Phylogeny. It must be fully recognised that any views which can be at present advanced upon this interesting, but very puzzling topic are at best little more than speculations, Formerly (/.c.), the writer inclined to the idea that all Haemoflagellates are to be derived from THE HAEMOFLAGELLATES 245 forms originally parasitic in Invertebrates; in other words, the Invertebrate was regarded as the primary host, the Vertebrate as the secondary or intermediate one. We now think this view was probably, to a considerable extent, wrong; in this we have been mainly influenced, on the one hand, by the intestinal 7rypanoplas- mata, and on the other, by the case of 7. grayi. As above remarked, it seems evident that a Vertebrate is the primary host of this latter parasite ; and the same would follow, by inference, for the other (Mammalian) Trypanosomes transmitted by Tsetse-flies. Moreover, the writer thinks he did not allow sufficient weight to the fact that the Invertebrates which harbour Trypanosomes are, with but few exceptions, blood-suckers. For these reasons we are now inclined to consider most of the Invertebrates concerned (e.g. leeches, many biting-flies, etc.) as the secondary, intermediate hosts of various Vertebrate parasites (probably all the Piscine and Amphibian ones, many, but perhaps not all the Mammalian ones, and perhaps some Avian ones). The only important! exceptions are among Insects; and here it is quite likely that we have both primary and secondary hosts. Besides the Tsetses, Tabanids, etc., the common house-fly and related genera, in which Herpetomonads (e.g. H. muscae-domesticae, Hf. sarcophagae, ete.) occur, ought apparently also to be placed in the category of secondary hosts. For Prowazek (l.c.) states that, according to Brauer, the latter flies are probably de- scended from blood-sucking ones; in which case their parasites may very well be descended from haemal forms, which are now, perforce, restricted to the Invertebrate host. On the other hand, there are several instances of the parasites occurring either in non- sanguivorous Insects or in forms that only rarely suck blood, which are, we think, more likely cases of primary parasitism. Among these, for example, are H. bombycis, in Bombyx mori; H. gracilis, in larvae of Tanypus; Crithidia campanulata, in larvae of Chironomus plumosus. Lastly, we have the mosquitoes and their parasites, both of imago and larva. The latter is, of course, aquatic, and the imago is by no means limited to blood for nutri- ment. Having regard also to the illustrative series of transitional forms between the monadine type and the trypaniform one, made known by Léger and others, it appears to us that here as well the Insect is the primary host of the various Flagellates concerned, and that where these are connected with a Vertebrate host the latter is to be regarded as the secondary, intermediate one. This would apply chiefly to certain parasites (eg. Zrypanomorpha) of birds, though not necessarily, it is to be noted, to all. Many authorities (such as Laveran and Mesnil, Liihe, Novy and 1 Herpetomonas biitschlii from a Nematode (Trilobus) and the curious Trypano- phis from Siphonophores do not appear to have any bearing upon this question. 246 THE HAEMOFLAGELLATES M‘Neal) have maintained the view that the Invertebrate is the primary host in all cases. Minchin, however, has always considered the Vertebrate as the principal host; and in his latest memoir on the Trypanosomes of Tsetse-flies (58), proofs of which he very kindly allowed the writer to see, he regards all Trypanosomes as descended from an intestinal Vertebrate form, and indicates the lines upon which the evolution may be supposed to have advanced. This ancestral form produced resistant cysts for dispersal, and thus contaminative infection was brought about. (It would be extremely interesting to ascertain whether the intestinal Zrypanoplasmata known (see p. 249) have such a cyst-formation.) The next stage in evolution is when the parasite has penetrated the intestinal wall, and come into relation with the circulatory system. Until it came into relation with a blood-sucking Insect, this type would have to pass back into the alimentary canal for dissemination. So far, we have no evidence of an existing instance of this stage. Subsequently, the blood-parasite became adapted to an Insectan host, in the gut of which it encysted, reinfection of the Vertebrate being by the contaminative method. 7. grayi in all probability furnishes an example of this type. Lastly, the parasite is thoroughly adapted to the biology of the Insect and passes forwards to the front part of the alimentary canal: infection of the Vertebrate is now by the inoculative method. This may possibly be combined in some cases with the contaminative mode, but probably in most encystment no longer takes place, being unnecessary (¢.g. the lethal Trypanosomes, Piscine forms, etc.). Of course, in those cases where, as above remarked, the Verte- brate is probably the secondary host, there is no reason to suppose that, as a rule, the parasites leave the circulatory system. Phylogeny.—As stated at the beginning of this article, the Trypanosomes, as a whole, are to be regarded as including two entirely distinct families, in one of which (the Monadine type) the attached flagellum becomes free at the true anterior end, and in the other (the Heteromastigine type) at the true posterior end. The former type is derived by the progressive migration backwards of the kinetonucleus towards the posterior (aflagellar) end, in the manner well illustrated by Léger’s series of Herpetomonadine forms (see Fig. 29). The latter type is derivable from a 'Trypanoplasmatine ancestor—itself in turn doubtless to be derived from a Bodo-like form—by the loss of the anterior free flagellum ;! so that the non- flagellate extremity is the true anterior one. The writer is unable, owing to limits of space, to enter fully 1 A comparison of the different degree of development of the flagella in various forms is instructive as illustrating the manner in which the Trypanoplasmatine condi- tion may have resulted from that found in Bodo, and its further evolution. a YT 7.4 THE HAEMOFLAGELLATES 247 here into the reasons for and against this diphyletic view, which was first put forward by Léger (49). A complete discussion will be found in his Review of the Haemoflagellates (pp. 270-278). Liihe, in his account of the Haematozoa in Mense’s Handbuch der Tropenkrankheiten (2), has adopted it, though on somewhat different lines from those taken by us. Minchin, also, has expressed the opinion (Brit. Med. Journ., 1907, 11. p. 13820) that Trypanosomes are most likely diphyletic. On the other hand, many authorities, including Laveran and Mesnil, hold the view that all ‘Trypanosomes are descended from Herpetomonadine ancestors, basing their opinion on the resemblance to a Herpetomonad shown by many Trypano- somes in cultures, and by young individuals of 7’ lewisi (cf. Fig. 20). In many cases, at any rate, we regard this phase—as we have previously said—rather as a ‘‘ pseudo-Herpetomonadine ” condition ; and in such cases do not attribute to it the phylogenetic importance which is done by some, but consider it to be probably capable of explanation on other grounds (see /.c.). A fact which seems to us of considerable significance is that Trypanoplasmatine forms are known to occur in the digestive tract of fishes, e.g. “‘ Trypanoplasma ” intestinalis in Box boops, and “T.” ventriculi in Cyclopterus lumpus ; moreover, another Heteromastigine parasite (Dodo lacertae) is found in a lizard. On the other hand, no indubitable Herpetomonad has yet been described from the alimentary canal of a Vertebrate, which we may assume to have been the oinal habitat of the primitively Vertebrate parasites. Hence, all things considered, we come to the general conclusion that the Trypanosomes which have the Vertebrate for their primary host are Heteromastigine forms; those derived from primitively Invertebrate parasites, on the other hand, are probably Monadine forms. Endeavouring to use this view practically, for purposes of classification, or, at any rate, of convenient partition of the Trypano- somes, we have as follows: — The parasites of fishes belong to the Heteromastigine type; this can be said with some degree of confidence, in spite of the ‘“ Crithidial” forms assumed by the parasites in leeches. Probably the same is true also of most forms of cold-blooded Vertebrates. Of the Avian ones, on the contrary, some at any rate (e.g. those of the type of Trypanomorpha noctuae) are Herpetomonadine forms. Among Mammalian parasites the various lethal Trypanosomes (e.g. 7. brucii, etc.) are to be regarded as Heteromastigine forms. We will only mention in passing that certain movements of these forms in the living blood (ef. p. 217) suggest very forcibly that the aflagellar end is the true anterior extremity. Of the other known (accustomed) parasites of Mammals, whose number has considerably increased of late, it is quite possible that some (¢.g. those of bats, which may have, perhaps, mosquitoes as their alternate hosts) are Herpetomonadine forms. 248 THE HAEMOFLAGELLATES 8. SYSTEMATIC. The reasons for the division of the Trypanosomes into two distinct families have been alluded to in the previous section. Besides the fundamental diagnostic characters, namely, the true orientation of the body and the biological features associated there- with, it is quite likely that important differences in regard to the life-cycle will become evident as our knowledge increases. SuUB-ORDER MONADINA. Family TRYPANOMORPHIDAE, Woodcock. — Haemoflagellates — derived from a uniflagellate, Herpetomonadine form, in which the point of insertion of the flagellum into the body has travelled back- wards from the anterior end for a considerable distance, the flagellum itself having become, concurrently, attached to the body for part of its length by means of an undulating membrane. At present only one genus is distinguished. Genus Zrypanomorpha, Woodcock. With the characters of the family. The genus was founded for Schaudinn’s Avian parasite, Trypanosoma (Halteridium) noctuae (Celli and San Felice),! from Athene noctua and Culex pipiens. As above mentioned, it is probable that other Avian forms, and perhaps some Mammalian ones, will be found to agree with this generic type; at present, however, it is not possible to say which with any certainty, and hence they are retained under the heading “ Trypanosoma.” Reference has been made to the possibility of Léger’s Crithidia fasciculata from Anopheles maculipennis, and other Insectan parasites which show marked trypaniform characters, being also really Haemoflagellates. In such a case the genus 7rypanomorpha may prove to be synonymous with Crithidia ; if so, the latter name will take priority. Liihe, it is to be noted, in his account of the Haematozoa (l.c.), regards all the Trypanosomes of Mammalia as belonging to the Herpetomonadine type, and has proposed the new generic name 7'rypanozoon for these forms. SuB-ORDER HETEROMASTIGINA. Family TRYPANOSOMATIDAE, Doflein. — Flagellates, with but few exceptions haemal parasites, derived from a biflagellate, Bodo- like type, in which the posteriorly directed (trailing) flagellum is always present and attached to the side of the body by an undu- lating membrane, of which it constitutes the thickened border. 1 Schaudinn placed this form in the genus 7’rypanosoma. We incline, however, to the view that the type-species of that genus (7. rotatorium) is a Heteromastigine type, and therefore restrict that genus to such forms, \ a THE HAEMOFLAGELLATES 249 The other, the anterior flagellum, may or may not persist. At least three genera known so far. Genus Zrypanoplasma, Laveran and Mesnil. The anterior flagellum is present. Type-species, 7. borreli, Lav. and Mesn. (Fig. 11). Length of body 20-22 p, of free flagella 13-15 py, breadth 343-44 p. Parasitic in Leuciscus erythrophthalmus, rudd, and Phowinus laevis, minnow. Other species are 7. cyprini, from the carp, and 7. variwn, a rather larger form, from the loach. Genus 7rypanophis, Keysselitz. The anterior flagellum is pre- sent. The free part of the posterior flagellum is short, and the undulating membrane is straight and relatively narrow. ‘The species for which this genus was founded is parasitic in certain Siphonophores, and almost certainly not a haemal form. €.0- - ~ Fia. 30. Trypanophis grobbeni (Poche). e.c, ectoplasmic cap ; ¢.1, delicate ectoplasmic layer, thin- ning out posteriorly ; 7, inclusions in the cytoplasm ; z, nuclear body of uncertain origin and significance. (After Keysselitz. ) Type-species, 7. grobbena (Poche). Average length 60-65 pu, width about 4 wp. From Cucubalus kochit, Halistemma tergestinum, Monophyes gracilis, Gulf of Trieste. Apparently the same parasite has also been observed in Abyla pentagona, Gulf of Naples. The organisms are to be found in all the ramifications of the coelenteron, from the digestive-cavity of the gastrozoids to the radial canals of the medusoid buds. Nothing is known with regard to the transmission from one Siphonophoran colony to another. Great interest attaches to certain Trypanoplasmatine parasites recently described from the alimentary canal of fishes. In their general morphology and the possession of an undulating membrane they agree closely with Z7rypanoplasma, and their describers have included them in this genus, as 7’ intestinalis, Léger, and T. ven- 250 THE HAEMOFLAGELLATES triculi, Keysselitz. So far as those points are concerned, however, they agree also with the above-mentioned genus Trypanophis (cf. Figs. 30 and 31). Indeed, Léger, in his account of 1’. intestinalis, commenting on the great resemblance of this parasite to 7rypanophis, suggested that the latter form might be included in 7rypanoplusma. We consider that Zrypanophis grobbeni, on account of its curious habitat and somewhat peculiar nature, should certainly be kept distinct. More- over, as regards the intestinal Trypanoplasma- tine forms, the fact that they are most likely not haemal parasites renders it very probable that their life-cycle differs in many ways from that of the blood-7rypanoplasmata (cf. the hypo- thetical stages in evolution outlined above, ia. 31. p. 246). Formerly, we placed “ 7.” intestinalis “Trypanoplasma” in- With T'rypanophis on these grounds ; but it seems nasi Meet poh preferable to consider it as belonging to an down the side near the independent genus, along with “7.” ventricult. undulating-membrane (cf. : : - Trypanophis); in B the As we are averse to the practice of instituting kinetonucleus is double. a - j (After an original draw- NeW genera in a treatise, we do not propose to ing kindly lent by Prof. pa: do so here. Before leaving this point, it may be noted that, in the case of these Heteromastigine forms, the presence of an undulating membrane and consequent trypaniform appearance does not bear the same relation to a haemal habitat as seems to be the case in the Monadine types. As Doflein has already pointed out,! the undulating-membrane, in the Trypanoplasmatine parasites, has doubtless been developed as the result of the contiguity of the trailing flagellum of the Bodonine type to the side of the body ; a quite different origin from that in the other section. Hence this condition is more or less independent of the habitat of these forms. Genus 7'rypanosoma, Gruby (principal synonyms:? Undulina, Lank., 1871; Herpetomonas, Kent, 1880, but only in part, since the type-species is J/. muscae-domesticae; Paramoecioides, Grassi, 1881; Haematomonas, Mitrophan., 1883; Zrypanomonas, Danil., 1885, for young forms). There is no anterior flagellum. The point of insertion of the attached (posterior) flagellum into the body, and, consequently, the commencement of the membrane, may be anywhere in the anterior half of the body, but is usually near the extremity.’ 1 Die Protowoen als Parasiten und Krankheitserreger (Fischer, Jena, 1901), p. 54. 2 For remarks on the synonymy of this genus, readers are referred to the writer's previous article (p. 287). % The type-species is 7. rotatorium, Mayer, of frogs. At present, unfortunately, this parasite cannot with certainty be included in the above diagnosis, owing to its THE HAEMOFLAGELLATES 251 The sub-classification of this genus, or rather the grouping and arrangement of the numerous Trypanosomes at present included in it, is a question of great difficulty and one in regard to which hardly anything has been done as yet.! This is chiefly owing to the fact that so little is still known of the life-history of most that hitherto any attempt to group the parasites has been dependent upon their adult morphology. This is not a very satisfactory criterion, since, as we have seen, on the one hand, the differences in this respect between different forms may be very slight ; and on ‘the other, a particular parasite may itself vary very greatly at different times and under different conditions (see under ‘“ Morphology ”). Moreover, it may very well be that as more life-histories come to be revealed, some of the forms at present placed for convenience in C. x Fig. 32. A, Trypanosoma gambiense (from the blood), after Bruce and Labarro; B, 7. equinwm, after Lignieres ; C, 7. evansi, from an original drawing; D, 7. equiperdum, after Lign. the genus Z7rypanosoma will have to be transferred to new ones (as an example may be mentioned 7. gray). For the present, at any rate, a very useful aid towards dis- tinguishing different species is furnished by the biological relations of the parasites. or it may be assumed that here, as is usual among the Sporozoa, a particular species is, in general, restricted either to one particular host, or, at most, to a few allied ones. Difficulty arises in considering the Mammalian forms, many of which have never been observed in the true, natural hosts, but only unusual shape, position of kinetonucleus, etc. The occurrence, however, of an allied form in Hyla, which is evidently intermediate between 7’. rotatorium and the more typical, fusiform species, suggests that the former also belongs to the Hetero- mastigine section. 1 Koch, however, has attempted a classification of the Mammalian forms, which he arranges in two groups, the first including such different forms as 7. lewisi and the large 7. theileri of cattle; the other, most of the lethal forms, which he considers are not distinct species. his arrangement is very artificial and has nothing to recommend it. 252 THE HAEMOFLAGELLATES in various unaccustomed animals, for which they are more or less lethal. The important immunisation experiments first carried out by Laveran and Mesnil, and since then by other workers, have shown, however, that several of the parasites causing the different trypanosomoses now known are distinct species. A full description of all the known forms and their characteristics is impossible within the limits of this article. It must suffice to mention some of the more important and better-known parasites, arranged under the different classes of Vetebrate hosts ; for fuller details regarding them, reference should be made to the writer’s previous account, or to Nabarro’s revised edition of Laveran and Mesnil’s treatise, which is most useful in E: Fic. 33. A and B, T. theileri; C-E, T. “‘transvaaliense.” x 1250. (After L. and M.) this connection. A list of known hosts and their Trypanosomes is given at the end of this chapter. (a) Parasitic in Mammals. Trypanosoma lewisi, Kent, the common natural parasite of rats (Figs. 7, A; 20, a). Length! 24-25 p, breadth 14-2 y. This species is characterised by its narrow and pointed aflagellar extremity, and by the position of the trophonucleus in the flagellar half or third of the body. The cytoplasm is usually free from granules. T. brucit, Plimmer and Bradford, Length 28-30 p, breadth 2-2} pw. The anterior end is usually bluntly rounded (Figs. 7,8 ; 17, 4). The cytoplasm often contains granules in the posterior half. Natural hosts probably various Antilopidae (e.g. gnu, “ koodoo,” ete.), and buffaloes. The cause of Nagana or Tsetse-fly disease in cattle, horses, etc., in South Africa. 7. gambiense, Dutton (Syn. 7. ugandense, Castell), Length 21-23 p, breadth 14-2 p. This species (Fig. 32, a), according to its average size, is one of the smallest known, ‘The cause of human trypanosomosis in West and ! The dimensions given are intended to indicate the average size of the parasite in each case, but can only be considered as approximate. The length is inclusive of the flagellum, unless otherwise stated. THE HAEMOFLAGELLATES 253 Central Africa. The earlier stages of the disease, when the parasites are confined to the blood, are known as Trypanosoma-fever ; the later ones, after the organisms have penetrated into the cerebro-spinal canal, constitute the deadly malady of sleeping-sickness. The true, natural host is unknown, T. equinum, Voges (Syn. T. elmassiani, Lign.). Length 22-25 yp, width 14-2 y. Distinguished from all other forms by the minute size of the kinetonucleus (Fig. 32, B). Hydrochoerus capybara is almost certainly a natural host. Other well-known lethal parasites are: 7’. evansi (Steel), of Surra in horses in Indo-Burmah (Fig. 32, c) ; 7. equiperdum, Doflein (Syn. T. rougeti, Lav.), the cause of Dourine in horses, transmitted naturally by coitus (Fig. 32, p); 7’. thedlerv, Laveran, a very large form, often surpassing 50 m in length, which causes “ bile-sickness” of cattle in the Transvaal (T. transvaaliense, Lav., with the kinetonucleus near the middle of the Fic. 34. Fie. 35. T. johnstoni. g, deeply-staining granule at A Trypanosome from Sene- distal extremity of flagellar border. x 1500. gambian birds. x 1500. (After (After Dutton and Todd.) D, and T.) body (Fig. 33, c—E), has been shown to be, in all probability, only a phase of T. theilert); and T. dimorphon, Dutt. and Todd, which gives rise to a trypano- somosis of horses in Senegambia. (b) Parasitic in birds. T. aviwm, Danil., Lav. emend., probably the form to which Danilewsky’s original investi- gations related, occurring in owls and, according to Novy and M‘Neal, in various other birds. Length 35-45 p (Fig. 7, F). T. jgohnstont, Dutt. and Fic. 36. Todd. Length 36-38 p, width 14 p. T. paddae, At the base of the flagel- This parasite is so slender as almost \,,j5 (a tees Pam to justify the description spirochaeti- form (Fig. 34). From Estrelda, The opposite extreme of form is. seen in a Trypanosome, 7. hannae, Pittaluga, originally described by Hanna (25) from an Indian pigeon (Fig. 7, @); this is relatively very broad, and has, moreover, a long, attenuated aflagellar extremity, the latter character being not unusual in bird-Trypanosomes. On the other 254 THE HAEMOFLAGELLATES hand, Dutton and Todd have described a wide form from Senegambian birds, which has this end bluntly rounded, giving the parasite a stumpy appearance (Fig. 35). It is interesting to note that this Trypanosome occurred in the same birds (Estrelda) in which the very different 7. johnston was found. T. paddae (Fig. 36), from the Java sparrow, has been studied by Thiroux (83), and apparently lends itself to cultivation and inoculation into other birds as readily as do many Mammalian forms. Finally, there is the remarkable parasite, “7.” (Spirochaeta) ziemanni, described by Schaudinn. If this form is really a Trypanosome, it certainly belongs to the Heteromastigine section, and may for the present be placed in the genus Trypanosoma. But it may be, after all, a true Spirochaete, and belong to the Bacteria (cf. footnote, p. 237). (c) Reptilian forms. Scarcely any Trypanosomes have been observed in Reptiles. The only one which has been figured is T. damoniae, Lav. and Mesn, Length 32 p, breadth 4. The general structure (Fig. 7, J) presents nothing unusual. As in Piscine forms, the body is often rolled up on itself. From Damonia reevesti, a tortoise. Another form (T7’ bouetz), lately described from a lizard, is said to resemble the flat, smooth type of T. rotatoriwm (below). (d) Parasitic in Amphibian hosts. The Trypanosomes of frogs show a remarkable variation in form, size, and appearance, and it is not at all certain, in some cases, how far this is due to polymorphism, and how far to distinct species being concerned. The type-species of the genus is T. rotatorium (Mayer). (Synn. Amoeba rotatoria and Paramoeciwm costatum or loricatum, Mayer, July 1843; Trypanosoma sanguinis, Gruby, Nov. 1843; Undulina ranarum, Lank., 1871.) Laveran and Mesnil have worked on this form and dis- tinguish two principal types, one having the surface of the body thrown into parallel ridges (Figs. 8, B; 387, A), the other having a smooth, regular surface (Figs. 8, A ; 37, B). The parasites are very large, being 40-60 yu in length, by from 5-40 p» in width; the two dimensions vary more or less in- ; versely. The great variation in Fia. 37. shape of the body and of the 7 raetorter Otare,. Bithel ent mecet® anterior end is seen oma figures. The kinetonucleus is usually situated some distance from the non-flagellate or anterior extremity, and may be quite close to the trophonucleus ; sometimes, however, it is fairly near the end. Chiefly for this reason, Franca and Athias (22) split up the species into two, T. costatum or loricatwm (Mayer), with the kinetonucleus near the centre, and 7’. rotatoriwm, with it near the end. As the position of this organella is very variable and intermediate stages oceur, we do not think anything is gained by doing this, at present. Similarly, the validity of two new species which Franca and Athias THE HAEMOFLAGELLATES 255 create, namely, 7. wndulans and 7’, elegans, is somewhat doubtful. Dutton and ‘Todd have described two very long forms from Gambian frogs, which they have named 7. mega and T. karyozeukton; these forms exhibit peculiarities in the cytoplasm (see p. 212), and in the latter parasite a chain of chromatic granules runs from one nucleus to the other (Fig. 8, p). A type which is certainly distinct is 7. inopinatum, Sergent, from the edible frog. This parasite (Fig. 8, c) is slender (25-30 p by 3 p), and resembles a Mammalian or Piscine form. Another well-characterised species is 7. nelspruitense, Lav., in which the body is very vermiform and the free flagellum. very long (Fig. 8, &). (e) Forms parasitic in fishes. Trypanosomes occur very frequently in fishes, and a great many species have been described. J. remuki, Lay. and Mesn. This para- site occupies about the same position among Piscine Try- panosomes as does 7. lewisi among Mammalian ones. It is a slender form, with taper- ing, pointed extremities. The trophonucleus is in the pos- terior half of the body. Para- sitic in Hsox lucius, the pike. Fig. 38. Laveran and Mesnil have dis- seen ary’ tea ie x 1200. tinguished two varieties, based upon the considerable differences in size met with, namely, var. parva, medium length 30 yp, of free flagellum 10-12 p, with breadth 14-2 4; and var. magna (Fig. 8, L), minimum length 45 yp, of which 17-20 p is for the flagellum, and breadth 2-23 pw. T. cobits and T. carassit (Mitrophanow) | were among the first Piscine forms to be described, and probably corre- spond to many of those seen by Danilewsky. | 7. granuloswm of the eel is a remarkably long, eel-like form (Fig. 8, K), 70-80 u by 23-3 p. The kinetonucleus is relatively very large, as is often the case in Piscine furms, and close to the anterior end, which is sharply acute. Several forms have been observed in flat-fish, certain of which (eg. T. flesi, Lebailly) belong to a different type, being relatively wide, with only a short flagellum. From Elasmobranchs, two very large forms (7. scylliz and T. ravae) have been described by Laveran and Mesnil; these attain a length of 70-80 », and usually have the body coiled up on itself (Fig. 38). APPENDIX. (A) THe “ LeEISHMAN-DoNOVAN-WricHT” Bopizs. Although these remarkable bodies have not been shown yet to possess an actual trypaniform structure, the fact that they are known to give rise to Flagellate phases of very Herpetomonadine character points so conclusively to their connection with that type of parasitic Flagellate, and is of such importance as proving that a parasitic Flagellate \ 256 THE HAEMOFLAGELLATES can and does become intracellular in -the Vertebrate host, that a brief consideration of them is essential to the completeness of this article. The Leishman-Donovan bodies are constantly found in certain tropical fevers (such as Dum-dum fever, Kala-Azar), particularly pre- valent throughout Indo-Burmah, of which they are now generally admitted to be the cause. ‘These parasites were discovered by Leishman in 1900, but before his first account of them was published (91) they were also seen independently by Donovan. Moreover, organisms very similar to these parasites (indeed, morphologically, the two kinds are hardly distinguish- able) are found in various sores or ulcers (known as Delhi boil, Oriental sore, ‘bouton d’Alep”), to which people in differeut parts of the tropics are liable. The latter were first clearly recognised and described by Wright (97). In the former type of disease, there is a general systemic infection, the parasites spreading to all parts of the body, and being met with in the spleen, where they are usually very abundant, liver, bone-marrow, and (more rarely) in the peripheral circulation. The latter type of disease, on the other hand, is one of localised infection, the organisms being restricted to the neighbourhood of the skin lesions; and in this case the parasites never seem to become distributed throughout the body, producing a systemic infection. For this reason, though the organisms in the two cases seem to be undoubtedly closely related, they are probably specilically distinct. In the Vertebrate host, the parasites are generally intracellular. Free forms are met with, doubtless liberated by the break-up of the host-cells, but these probably soon invade fresh cells. Leishman’s form is parasitic in large uninuclear leucocytes (Fig. 39, II), and especially in cells of the vascular endothelium, which are often packed with the little bodies, becoming greatly distended (as macrophages). According to both Donovan (88) and Laveran and Mesnil (90), the parasites also occur in the red blood-corpuscles. Wright's form occurs in the ulcer cells, and in large migratory corpuscles (phagocytes) of the granulation- tissue. The parasites themselves are very minute, and usually ovoid or pyriform in shape, the latter being perhaps the more typical. The splenic form is somewhat smaller than the localised type, being 34-4 u in length by 14-2 p» in width (39, I), while Wright’s form is about 4 by 3 p» (39, Ill). The cytoplasm is finely granular and fairly uniform in character; but sometimes it is vacuolated. The most interesting point about the morphology is the fact that two chromatic bodies, of very unequal size, are invariably to be recognised. The larger nuclear body, which corresponds to the trophonucleus of an ordinary Haemoflagellate, is usually round or oval; the smaller one, representing a kinetonucleus, has the form either of a little rod or of a round grain, and stains very deeply. The two nuclei are generally quite separate, but sometimes they appear to be connected. The organisms multiply in two ways: (a) by binary fission, and (b) by multiple division or segmentation. The chief stages in the first method are well known (Fig. 39, I, b); they offer great resemblance to the corresponding process in Piroplasma, Multiple division has not yet been so satisfactorily made out. It appears to conform more THE HAEMOFLAGELLATES 257 or less to the radial or rosette type of multiplication (I, c), enlarged rounded parasites, with a varying number of nuclei (up to about 10) uniformly arranged near the periphery, having been often noticed. The details are, however, rather differently described by different workers, Our knowledge of any further development undergone by these parasites is limited at present to the Leishman-Donovan bodies, and is due in the first instance to Rogers (94). Rogers cultivated the parasites fe Fia. 39. I, Leishmania (Piroplasma) donovani (Lav. and Mesn.). a, typical pear-shaped or oval forms ; b, various stages in binary fission ; ¢, nuclear division, preparatory to multiple fission ; d, endo- corpuscular forms in red blood-corpuscles (p, pigment grains) ; e, bacillary form of the parasite in a corpuscle; M, large macrophageal cell with many parasites. (After Donovan.) II, Uni- nuclear leucocyte (L) containing several parasites. (After L. and M.) III, L. (P., Helcosoma) tropica (Wright). a, single individuals ; 6, dividing forms. (from Mesnil, mostly after Wright.) IV, L. (P.) donovani in cultures of different ages. a, ordinary forms of varying size ; b, c, stages in multiple division ; e, f, and g, flagellate forms. (After Rogers.) in citrated blood, at a lower temperature, and made the astonishing discovery that Flagellate forms were developed from them. This result has since been fully corroborated and further details ascertained by Christo- phers (87), Leishman and Statham (92), and others. Different stages in the process are seen in Fig. 39, 1V, d-g; and Fig. 40. The parasites increase greatly in size and become vacuolated (this is probably due to the artificial medium in which they are). Multiplication by binary fission takes place, and with successive generations the shape of the body alters ; from being pyrifourm it passes through a fusiform condition, and finally becomes elongated and slender. Meanwhile, in many of these phases, a 17 258 THE HAEMOFLAGELLATES flagellum has made its appearance; when this is fully developed the parasite quite resembles an ordinary Herpetomonas. The origin of the flagellum is interesting. A distinctive vacuole-like structure arises near the end which will become the flagellar end, in close connection with the kinetonucleus—a point, probably, of importance. This vacuole increases and suddenly is ruptured, some of its contents being extruded to the exterior as a tuft or fringe of pink-staining substance. In the middle of this, a small flagellum is seen, but how exactly it is formed is not known. Once constituted, the flagellum grows rapidly. Even in the most fully-developed Flagellate phases, however, in no case has anything comparable to an undulating-membrane been observed. The kinetonucleus is comparatively near one end of the body, Fia. 40. Stages in the development of the flagellated form. (From Leishman.) 1, ordinary spleen parasite ; 2, 8, growth and vacuolisation in cultivation ; 4, 5, appearance and growth of the special ‘‘ flagellar vacuole,” close to the kinetonucleus ; 6, rupture of this vacuole and protrusion of a tuft of pink-staining threads ; 7, growth of the flagellum, its base being inserted in the collapsed vacuole ; 8, acquirement of the Herpetomonad form. and the flagellum springs directly from that end, not being actually connected, apparently, with the former organella. Another remarkable process observed in these developmental forms in cultures is unequal longitudinal fission. Very thin, sickle-like (“ spirillar ”) portions of the body are split off from one side of a parent-individual. More than one of these thread-like forms may be successively cut off. The unusual feature of the process is that neither the two principal nuclear elements nor the flagellum take part in it. Subsequently, these fission forms seem to give rise to very slender flagellar ones. To what extent this represents a normal (natural) mode of multiplication is uncertain, No other stages have been observed in cultures, and the organisms degenerate and ultimately die off. The above facts demonstrated, how- ever, that the Leishman-Donovan bodies can undergo important changes outside the human host, and rendered it probable that they do so naturally, though whether in the free condition or in an alternate host was, until lately, quite unknown, The superficial position of the localised form (Wright’s type) points very strongly to infection by means of some biting Insect, and it is natural to infer that the same holds also for the THE HAEMOFLAGELLATES 259 splenic type, when its occurrence in the circulation is borne in mind. Here, again, Rogers gave the lead. This worker, finding that the parasites developed flagellar stages most readily in an acid medium, suggested (95) that the stomach of some blood-sucking Insect (such as a flea or bug) was probably the place where the above described extra-corporeal phases of the parasite’s existence would be found to occur. This has been recently proved to be the case by Patton (93), who has found the Flagellate phases in the bed-bug (Cimex rotundatus |macrocephalus]). It is most probable, therefore, that the infection of human beings is brought about by this Insect, which serves as an alternate host. The systematic position and affinities of this parasite have been much discussed. Leishman at first considered the organisms as representing involution-forms of Trypanosomes, being largely influenced by the two chromatin masses; in this view he was supported by Marchand and Ledingham. Later, he went farther and suggested that they perhaps represented an actual stage in a Trypanosome life-cycle. Laveran and Mesnil, taking more into account the general form and very suggestive binary fission, thought a new species of Piroplasma was concerned, and named the bodies Pzroplasma donovani ; in this view Donovan and others have concurred. Other authorities (e.g. Christophers, Ross, and Wright) thought they saw in the parasite an entirely different kind of Sporozoan. Ross called the splenic type Leishmania, and a little later, Wright termed the ulcer-form Helcosoma tropiewm. Recently, Rogers has placed the Leishman-Donovan form in the genus Herpetomonas, on account of the similarity in the Flagellate- phase. It is probably best to regard the parasites as generically new forms ; in this case the splenic form becomes Letshmania donovani and the ulcer- type, which is most lkely a separate species, L. tropica. The organisms are closely related, on the one hand, with the Herpetomonads, and on the other with the Piroplasmata. With regard to the parasites possessing, at some period or other, a trypaniform structure, the complete absence of an undulating-membrane in the cultural forms is no proof that one is not present under certain conditions in Nature. For, as already noted, many Trypanosomes, when “cultivated,” may have a very slight indication of a membrane or none at all. Nevertheless, it is by no means improbable that these parasites have remained solely Herpetomonad forms and have not developed the characteristics of a Trypanosome, The fact that the Flagellate-phase is only known to occur in the Invertebrate host, points very strongly to this being the original primary host. In this connection the Herpetomonas lately described by Patton from Culex pipiens (to which reference has been made above) is very interesting, because of the occur- rence of resting-phases resembling the Leishman bodies. Lershmania may well be a similar form which, parasitic in a sanguivorous Insect, has become adapted to the Vertebrate host in its resting, gregariniform phase, and perhaps never develops a trypaniform condition, or even an active flagellar phase therein. Turning to the other side, there can be little doubt that the Piroplasmata are intimately connected with the Leishman-Donovan-Wright bodies. The general agreement of the intra- cellular forms as regards appearance and binary fission has been noted 260 THE HAEMOFLAGELLATES above. In addition, there is the most important point that some species of Piroplasma are stated to show, at certain times, the same characteristic nuclear dimorphism. Schaudinn was the first to notice this, in the case of P. canis; and he was confirmed by Kossel and Weber. Since then additional observations to the same effect are recorded by other workers (e.g. Liihe) for various species. This being so, the Piroplasmata also are most probably to be derived from Flagellate forms.! (B) A word or two, lastly, with reference to the supposed connection of the Spirochaetae with the Trypanosomes. Besides the instance of Trypanosoma (Sptrochaeta) ziemanni, Schaudinn, in his great memoir (l.c.), was inclined to consider that other Spirochaetae (e.g. S. obermeiert of relapsing fever) were also only phases in the life-cycle of other Haemo- flagellates. Subsequently, however, as a consequence of his investigations on Spirochaeta plicatilis, the type-species, and other forms, he relinquished this view, finding that the latter were of a totally different nature, and should rather be placed with the Bacteria. Much has since been written with regard to the nature and affinities of the various Spirochaetae. We do not propose to go into the general question here, as the preponderance of opinion is decidedly against these organisms belonging to the Protozoa. It is only necessary to mention one or two forms which have been definitely referred to the Trypanosomes. Certes, in 1882, described a parasite from the digestive tube, including the crystalline style, of oysters, which he named Trypanosoma balbianit. A few years ago Laveran and Mesnil (99) re-examined this organism, and came to the conclusion that it was not a Trypanosome but a Bacterium, allied to Spirochaeta. Other workers who have recently observed this form also agree that its structure shows none of the essential features of a Trypanosome, but, on the contrary, greatly resembles that of a true Spirochaete. Perrin, it may be noted, has endeavoured (100) to connect it with Schaudinn’s bipolar ‘* Ur- haemoflagellate.” This idea has received no support, and indeed Perrin’s whole paper is most unconvincing. Another, much more important example is that of the remarkable spirochaetiform parasite first described by Schaudinn and Hoffmann (103) in cases of syphilis, and which is now considered to be most likely the cause of that disease. Schaudinn found (102) that this organism differs in many ways from an ordinary Spirochaeta, and placed it in a new genus Treponema as T. pallidum. In a recent memoir (101), Krzysztalowicz and Siedlecki have given a detailed account of this organism, and state that they have observed distinct trypaniform stages in its life-cycle. For this reason they con- sider it to be allied to the Trypanosomes and place it actually in the genus Trypanosoma, as T. luis, This view lacks, as yet, corroboration, and so here, as in the case of Schaudinn’s research, the question must 1 Since this was written we are able to add that confirmation of this view is forth- coming. In a most important note, Miyajima (Philipp. J. Sci. ser. B, ii. 1907, p. 83) describes the development of Flagellate-phases in cultures of a Piroplasma (cf. parvum) of cattle in Japan. In seventy-two hours, forms with well-developed undulating-membrane were numerous. The author seems to have carefully guarded against the possibility of this highly-interesting occurrence being due to undetected Trypanosomes present in the blood, THE HAEMOFLAGELLATES 261 be left unsettled. There is one point, however, which may not be without significance, namely, the considerable resemblance between the biology of this parasite in relation to its host (i.e. as regards mode of infection, habitat, connection with the lesions, ete.) and that of Trypano- soma equiperdum, the cause of Dourine or “ horse-syphilis” (cf. above, pp. 197, 206). POSTSCRIPT. As this article goes to press, a most interesting note by Roubaud (C.R. Ac. Sct., 24th Feb. 1908, p. 423) comes to hand. This worker has been investigating the relation between certain lethal Trypanosomes (T. gambiense, T. brucu, T. dimorphon, and others) and Glossina palpalis, and finds that the parasites undergo important changes as soon as they arrive in the proboscis of the Tsetse-fly. The kinetonucleus passes to the middle of the body, the undulating-membrane disappears, the flagellum becomes short and thickened, and the parasites quickly attach themselves to the wall of the proboscis by the flagellar end. The whole process may be accomplished, indeed, in five minutes. Moreover, active multiplica- tion goes on, and after a time an immense number of attached Trypano- somes are present throughout the entire proboscis, often grouped in masses or colonies. This ‘‘temporary culture” (culture d’attente) persists for two days in the case of 7. bruczi, and longer—up to five to six days—in the other forms. This remarkable development is apparently specific for Glossinae ; it only occurs in a small number, and is doubtless due to the influence of special properties of the salivary fluid. As Roubaud remarks, it prob- ably affords an explanation of the selective rdle played by the Tsetses in the. propagation of different trypanosomoses in Africa. Roubaud, how- ever, considers that these forms found in the proboscis are the only ones capable of giving rise to an infection in a Vertebrate after the lapse of twenty-four hours. This is going too far, in view of the facts now known with regard to the length of time Trypanosomes may live and develop in the digestive tract of Glossinae (cf. pp. 200, 230). It is noteworthy that Roubaud was unable to obtain a successful inoculation from a proboscis so infected. Moreover, the repeated failures of investigators to infect animals from flies after forty-eight hours (cf. pp. 199, 200) seem to show that the later-developed “ proboscis-forms”’ at all events are not infective, since they may reasonably be supposed to have been present in some of the many experiments tried. On the other hand, there is an important observation made by Bruce when working on 7. brucw, to which Minchin (58, p. 210) has drawn attention, showing that “wild” flies, caught while feeding on a healthy animal, could infect another animal on which they were subsequently fed. This certainly points to the presence of some developmental phases in the Insect other than Roubaud’s proboscis- forms ; the proboscis had been presumably ‘‘ cleaned” by the first bite— on the uninfected animal on which the fly was caught. And this view is entirely borne out by Stuhlmann’s recent research, summarised in the body of this article. 262 HOSTS OF THE HAEMOFLAGELLATES LIST OF KNOWN (NATURAL) HOSTS OF TRYPANO- SOMES AND ALLIED FORMS. [In the compilation of this list, Nabarro’s edition of Laveran and Mesnil’s Treatise has been of considerable service to the writer. ] MAMMALIA. ? Bovidae (Indian, indigenous) ? B. (various, African) Buffaloes ; : ‘ Catoblepas gnu, gnu, ‘* wildebeeste ” ? Cattle (‘‘ hill,” India) Cavia cobaya, guinea-pig Cricetus frumentarius (arvalis), hamster Hydrochoerus capybara, capybara Lepus cuniculus, rabbit Meles taxus, badger Miniopterus schreibersii, bat Mus decumanus, sewer-rat . MI. rattus, black rat, M. rufescens M. sylvaticus, field rat M. musculus, mouse . M. niveiventer, rat (Indian) Myotis murinus, a bat Myoxus avellanarius, M. glis, dormice Nesokia (Mus) giganteus, bandicoot Phyllostoma sp. See under Stegomyia Pipistrellus pipistrellus, bat : Pteropus medius, a bat Sciurus palmarum, squirrel (Indian) . Spermophilus guttatus, S. musivus, spermophile Strepsiceros capensis, ‘‘koodoo” Talpa ewropaea, mole , Tragelaphus scriptus sylvaticus, ‘ bush- buck” Trypanosoma evansi (Steel). T. theileri, Lav., and 7’. transvaaliense, Lav. [most probably = 7’. theiler7]. T. brucii, Bradford and Plimmer. T. brucit. T. himalayanum, Lingard (syn.+ 7. lingardi, Blanchard) [perhaps = T.. theileri). : A Trypanosome [possibly a Trypano- plasma], Kunstler, 1883. T. rabinowitschi, Brumpt (syn. Try- — panozoon criceti, Liihe). .T. equinum, Voges. T. cuniculi, Blanchard. T. pestanai, Bettencourt and Franea. A Trypanosome [Dionisi, 1899]. lewist (Kent); TZ. longocaudense, Lingard [probably = 7. lewis7]. T. lewisi (Kent). T. sp. [lewisi #7], Gros, 1845. 7’. duttoni, Thiroux ; 7. muscwli [syn. T. d.%), Kendall. F. longocaudense, Lingard [probably ' = T. lewisi]. T. nicolleorum, Sergent, E. and E. [perhaps syn. 7. vespertilionis, Battaglia]. T. blanchardi, Brumpt (syn. 7. myoxt, Blanchard). T. bandicotti, Lingard, T. sp. (compared with 7. nicol/eorum), Petrie. A Trypanosome [Donovan, in Lay. and Mesn., 1904]. T. (T'rypanozoon) indicum, Liihe. . A Trypanosome [Chalachnikov, 1888}. 7’. brucii, Br. and PI. T. talpae, Nabarro. T. brucii. HOSTS OF THE HAEMOFLAGELLATES Vespertilio kuhli, bat . V. noctula, bat . ‘ : ‘ Vesperugo natterert, V. pipistrellus (‘‘pipistrelle”’), V. serotinus, bats 263 7’. nicolleorwm, Sergent, E. and K, ; T. vespertilionis, Serg. [both perhaps synn. 7’. vespertilionis, Battaglia]. 7. vespertilionis, Battaglia. T. dionisii, Bettencourt and Franca [perhaps syn. 7. vespertilionis, Battaglia]. Various Trypanosomes which have been given distinct names have been lately described from certain Equidae and Bovidae in different regions of Africa, as the cause of more or less pronounced trypanosomosis. of other better-known African parasites, enumeration of species, for purposes of reference. It is probable that some of these, at any rate, are really forms They are mentioned here, in order to complete an They are T. cazalbowi, Lav. ; T. congolense, Broden; 7. nanwm, Lay. (an extremely small form); T. pecaudi, Lav. ; T. soudanense, Lav. ; T. suis, Ochmann ; and 7. vivax, Ziemann. The true (natural) hosts are uncertain. AVES. Agelaius phoeniceus, red-winged black- bird a Alcyon sp., kingfisher (Cameroon) Asturinula monogrammica, hawk (Congo State) Athene noctua, little owl A. brama, owl (Madras) Buteo lineatus, red-shouldered hawk Bycanistes buccinator, trumpeter horn- bill Chelidon urbica, house-martin Colaptus auratus, “‘ flicker” Columba sp., pigeon (Indian) Coracias garrula, roller-bird Corvus sp., crow or raven (Indian) Crane. : : : Crithagra sp., ‘‘millet-eater”’ Cyanocitta cristata, blue jay Dryobates villosus, hairy woodpecker . Keret . Emberiza citrinella, yellow-hammer Estrelda estrelda, ‘‘ millet-eater”’ Fringilla (Carduelis) carduelis, gold- finch F. coelebs, chaffinch Goat-sucker T. avium (type L. and M.), [Novy and M‘Neal, 1905]. A Trypanosome [Ziemann, 1905]. A Trypanosome [Dutton, Todd and Tobey, 1907]. Trypanomorpha (Trypanosoma) noc- tuae (Schaud.); also Trypanosoma [Spirochacta?] ziemanni (Lav.). A Trypanosome [Donovan, in Lav. and Mesn., 1904]. T. mesnili, Novy and M‘Neal. A Trypanosome [Dutton, Todd and Tobey, 1906]. A Trypanosome [Petrie, 1905]. T. avium (type Lav. and Mesn.). T. hannae, Pittaluga. T. ‘‘aviwm,” Danilewsky. A Trypanosome [Hanna, 1903]. A Trypanosome ? [Gros, 1845]. T. sp. [Dutton and Todd, 1903}. T. avium (type L. and M.); also 7. sp. [Novy and M‘Neal, 1905]. T. sp. incert. [Novy and M‘Neal, 1905). T. sp., perhaps aviwm [Cerqueira, 1906}. A Trypanosome [Petrie, 1905]. T. johnstoni, Dutton and Todd. T. sp. (Sergent, E. and E., 1904]. A Trypanosome [Ziemann, 1898 ; also Petrie, 1905]. A Trypanosome ? [Gros, 1845]. 264 HOSTS OF THE HAEMOFLAGELLATES Harporhynchus rufus, brown thrasher Hirundo rustica, swallow Icterus galbula, Baltimore oriole. Laniarius cruentus, shrike (African) . Linota (Acanthis) rufescens, redpoll Melospiza fasciata, song-sparrow . Merula migratoria, robin (American) . M. merula, blackbird . Milvus govinda, kite (Indian) Neophron percnopterus, vulture (African) Nicticorax gardenia (Brazil) Padda oryzivora, Jaya sparrow Passer domesticus, sparrow . Passerine birds, many (except cea and Pica) Polyplectrum (Annam) Scolephagus carolinus, rusty blackbird Sialia sialis, bluebird , Spinus tristis, goldfinch (American) Sylvia atricapilla, black-cap warbler Syrnium aluco, tawny owl . germani, pheasant T'achyphormus ornata . Treron calva, dove (Angola) Turdus musicus, song-thrush Troglodytes aedon, house-wren Zenaidura macroura, mourning-dove - A Trypanosome [Novy and M‘Neal, 1905]. T. mathisi, Serg., E. and E. ; a Try- panosome (7. m. *) [Petrie, 1905]. ° T. avium (type L. and M.). A Trypanosome [Neave, 1906]. T. sp. [original observation]. T. avium (type L. and M.). T. avium (type L. and M.). A Trypanosome [Petrie, 1905]. A Trypanosome [Donovan, in Thiroux, 1905]. A Trypanosome [Neave, 1906]. T. sp., perhaps aviwm [Aragao, in Cer- queira, 1906]. T. paddae, Thiroux. T. avium (type L. and M.). Trypanosomes [Sjibring, in N. and M ‘Neal, 1905]. T. polyplectri, Vassal. T. sp., Novy and M‘Neal. T. avium (type L. and M.). T. laverani, Novy and M‘Neal. T. sp. [Sergent, E. and E., 1904]. T. avium, Danil., emend. Lav. ; also “T.”’ [Leucocytozion] ziemanni (Lav.). A Trypanosome [Cerqueira, 1906]. A Trypanosome [Wellman, 1905]. A Trypanosome [Petrie, 1905]. A Trypanosome [N. and M‘N., 1905]. T. avium (type L. and M.). REPTILIA. Crocodile (Uganda) Crocodilus cataphractus ? (Congo) Damonia reevesii, tortoise . Gecko. : : ; : ; Mabuia raddonii, a lizard (French Guinea) Python Snake (unspec., Gambia) Tortoise (Indian—Zmys or Kachuga tectum) Tortoise (unspec., Gambia) A Trypanosome [Minchin, Gray and Tulloch, 1906}. A Trypanosome [Dutt., Todd and Tob., 1907]. T. damoniae, Lav. and Mesn. A Trypanosome [Gehrke, 1903]. T. boweti, Martin. ‘*T.” pythonis, Robertson [really a Haemogregarine]. A Trypanosome [Dutton and Todd, 1903}. A Trypanosome [Simond, in L. and M., 1904]. A Trypanosome [Dutton and Todd, 1903]. HOSTS OF THE HAEMOFLAGELLATES 265 AMPHIBIA. Bufo vulgaris and viridis, toads . B. reticulatus (Somaliland) . Diemyctulus — viridescens newt) Frogs (unspec., Gambia) (American Hyla arborea and H, viridis, tree-frogs H. lateristriga (?), Brazil Rana angolensis (Transvaal) R. esculenta, edible frog KR. temporaria : R. t. (2) (Hong Kong) . R. theilert (Transvaal) 2 : 2. trinodis (?) and other sp. (Gambia) 7’. rotatorium (Mayer), 7’. somalense, Brumpt. A Trypanosome [Tobey, 1906]. T. mega and 7. karyozeukton, Dutton and Todd. T. rotatorium (Mayer); 7. sp. [7], Lay. and Mesn. T. borreli, Marchoux and Salimbeni. T. nelspruitense, Lav. T. vrotatorium (Mayer). (Syn. 7’. loricatum or costatwm (Mayer) and T. rotatorium (Mayer), Franca and Athias ; 7’. 7. var. nana, Sergent, E. and K.; 7. inopinatum, Sergent, E.and E.; 7’. elegans and 7’, undu- tans, F. and A. [doubtful species].) T. rotatorium (Mayer). 7’. belli, Nabarro. 7’. nelspruitense, Lav. T. rotatorium (Mayet). ~ PISCES. (pl. = Trypanoplasma.) Abramis brama, bream Acerina cernua, pope . Anguilla vulgaris, eel Bageus bayard, bagara (Nile) Barbus carnaticus (India) B. fluviatilis, barbel . Blennius pholis, blenny , Bothus rhombus (Rhombus lave), brill Lox boops Callionymus eiconavhis Carassius auratus, goldfish C. vulgaris, Prussian carp . Clarias (Silurus) clarias, a Silurid (Cochin-China) C. angolensis (Congo State) Cobitis barbatula, loach ~ T. abramis, Lav. and Mesn.; 7'pl. abramidis, Brumpt. 7. acerinae, Brumpt; a Trypanoplasm [Keysselitz, 1906]. T. granulosum, Lay. and Mesn. A Trypanosome [Neave, 1906]. A Trypanosome [Lingard, 1904]. Theis,” — Brampt 3. Ppt: Brumpt. T. delagei, Brumpt and Lebailly. T’. bothi, Lebailly. Tpl. [2] intestinalis, Léger. T. callionymi, Brumpt and Lebailly. T. danilewskyi, Lav. and Mesn. T. carassti (Mitrophan.). (Syn. Haema- tomonas c., Mitr.; 7’. pisctwm and 7’. Susiforme piscium, Danilewsky.) T. clariae, Montel. barbi, A Trypanosome [Dutton, Todd and Tobey, 1906]. T. barbatulae, Léger; Tp. Léger. varium, 266 C. fossilis . Cottus bubalis ; C. gobio, river bull-head Cyclopterus lumpus, lump-fish Cyprinus carpio, carp. Esox lucius, pike Gobio fluviatilis, gudgeon G. giuris (India) Gobius niger, goby : - : Leuciseus (Scardinius), erythroph- thalmus, rudd or red-eye L. idus, L. cephalus, L. rutilus, roaches LI. spp. ; Limanda piacere , Lota vulgaris Macrodon malabaricus (Brazil) Macrones seenghala, M.tengara,Silurids (India) M. cavasius (India) Mugil sp., noke (Nile) Ophiocephalus striatus, Silurid dia) Perca fluviatilis, perch : : Phoxinus laevis, minnow Platophrys laternae : : Pleuronectes flesus (Flesus oul garis), flounder P. platessa (Platessa vulgaris), plaice . Polypterus sp., dabib (Nile) Raia clavata, R. macrorhynchus, R. mosaica, and R. punctata, rays hk. microcellata . Rhamdia queler (Brazil) Saccobranchus fossilis, a Silurid . Salmo fario, trout Scyllium canicula, S. stellare, dogfish HOSTS OF THE HAEMOFLAGELLATES T. cobitis (Mitroph.). (Syn. Haemato- monas c., Mitr.; TZ. pisctum and T. fusiforme, Danilewsky.) T. cottt, Brumpt and Lebailly. T. langeroni, Brumpt; TZpl. guernet, Brumpt. Tpl. [2] ventriculi, Keysselitz. T. danilewskyi, Lav. and Mesn.; Tl. cyprini, Plehn. T. remaki, Lav. and Mesn.; Z'pi. sp. [Minchin, 1908}. T’. elegans, Brumpt. T. sp. [Castellani and Willey, 1905]. T. gobii, Brumpt and Lebailly. Tpl. borreli, Lav. and Mesn.; T. scardinii, Brumpt. A Trypanosome and Trypanoplasm [Keysselitz, 1906]. [Probably Tl. borrelt and 7’. leucisci.] T. leucisci, Brumpt. T. limandae, Brumpt and Lebailly. A Trypanosome and Trypanoplasm ~ [Keysselitz, 1906]. T. macrodonis, Botello. A Trypanosome [Lingard, 1899]. A Trypanosome [Castellani and Willey, 1905]. A Trypanosome [Neave, 1906]. A Trypanosome [Lingard, 1899]. T. percae, Brumpt; also a Trypano- plasm [Keysselitz, 1906]. T. danilewskyi (2), Lav. and Mesn.; 7. phoxini, Brumpt ; Tpl. borreli, Lav. and Mesn. T. laternae, Lebailly. T. flesi, Lebailly (syn. nectidiwm, Robertson). T. platessae, Lebailly (syn. 7. plewro- nectidium, Roberston). A Trypanosome [Neave, 1906]. T. raiae, Lavy. and Mesn. T. pleuro- A Trypanosome [Robertson, 1906]. T’. rhamdiae, Botello. T. saccobranchi, Castellani and Willey. Tpl. truttae, Brumpt. [Valentin, in 1841, observed a Haematozoan, which was probably either a Trypanosome or a Trypanoplasm. } T. scyllii, Lay. and Mesn, HOSTS OF THE HAEMOFLAGELLATES 267 Silurus glanis Solea vulgaris, sole Squalius (Leuciscus) cephalus, ahib Synodontis schal, gargur (Nile) Tinca tinca, tench Trichogaster fasciatus (India) A Trypanosome [Keysselitz, 1906]. 7’. solewe, Lav. and Mesn. 7’. squalid, Brumpt. A Trypanosome [Neave, 1906]. 7’. tincae, Lay. and Mesn. ; a Trypano- plasm [Keysselitz, 1906]. A Trypanosome [Lingard, 1899]. INSECTA. Anopheles maculipennis A. m. (larvae) Anopheles sp., mosquitoes (India) Bombyx mort, silkworm Chironomus plunosus Cimex rotundatus, bed-bug inci) Culex fatigans C. pipiens . Dasyphora pratorum . Glossina fusca G. morsitans and G. ae ee G. palpalis G. tachinoides Haematopinus Paniecus tat Trae Haematopota ttalica Hippobosca rufipes, (?) Homalomyia scalaris . : Melophagus ovinus, sheep-louse . row ee Musca domestica . Nepa cinerea Pollenia rudis Pulex sp., fleas Sarcophaga haemorrhoidalis, og Stegomyia fasciata . S. f. (an individual which find fed on a bat, Phyllostoma) Stomoxys calcitrans Tabanus glaucopsis Crithidia fasciculata, Léger. A Herpetomonad (cf. with H. jaculwm) [Sergent, E. and E., 1906]. Herpetomonads (said to resemble Leger’s Crithidia) [Ross, 1898 ; Christophers, 1901, and others]. Herpetomonas bombycis, Levaditi. Crithidia campanulata, Léger. Leishmania (Piroplasma) donovani. Herpetomonads [Ross, 1898 ; Chris- tophers, 1901 ; Patton, 1907]. Trypanomorpha noctwae (Schaud.) ; Crithidia fasciculata ; ‘‘ Trypano- soma” (Herpetomonas) culicis, N., M‘N., and Torrey ; H. algeriense, Sergent, E. and E.; H. sp., indet. [Patton, 1907]. H. lesnet, Leger. T. brucii ; perhaps 7’. gambiense. (2) 7". brucit. T. grayi, Novy ; T. tullochit, Minchin ; (2) T. dimorphon, Dutt. and Todd. (2?) T. bructi ; (2) T. gambiense. (2) T. lewist. (2) H. subulata, Léger. T. theilert (probably). H. (cf. muscae-domesticae) [Léger]. “' Trypanosome-like parasites ” [ Pfeiffer, 1905]. H. muscae-domesticac, Burnett. H. jaculum, Léger. H. (cf. m.-d.) [Léger]. T. lewisi (probably) ; a Herpetomonad [Balfour, 1906]. H. sarcophagae, Prowazek. H. algeriense, Sergent, E. and E. A ‘“‘Trypanosome” [Durham, 1900]. (2) T. equinum; a Herpetomonad [Gray, 1906]. H. subulata, Léger. 268 HOSTS OF THE HAEMOFLAGELLATES T. lineola and other sp. T. tergestinus Tanypus sp. Theicomyxa fusca ‘* Water-bug”’ (India) Rhipicephalus sanguineus, (India) Calobdella punctata Helobdella algira Hemiclepsis marginata HH. Spe Piscicola sp. P. geometra Pontobdella muricata . P. sp. (?) Z. evansi. Herpetomonas (Crithidia) minuta, Léger. H. gracilis, Léger. . -.H. (cf. m.-d.) [Léger]. A Herpetomonad [Patton, 1907]. ARACHNIDA, ‘‘T.” christophersi, N., M‘N., and Torrey. HIRUDINEA. T. cotti and 7’. soleae [Brumpt]. T. inopinatum [Billet]. Tpl. varium [Léger]. “ T. abramis, acerinae, barbi, dani- lewskyi, granulosum, percae, phoxini, remaki, squalii; perhaps also 7. barbatulae (2), langeroni, leucisci, scardinii[Brumpt]. TZpl. abramidis [Brumpt]. T. barbatulae [Léger]; Tpl. borreli, barbi, guernet, (?) truttae [Brumpt]. Tpl. borreli ; also other Trypanoplasms [Keysselitz]. T. raiae [Robertson]. T. scyllit [Brumpt]. SIPHONOPHORA. Abyla pentagona, Cucubalus kochii, | Trypanophis grobbeni (Poche). Halistemma tergestinum, and Mono- phyes gracilis : LITERATURE. I. Relating to the Trypanosomes. A. Comprehensive works. 1. Laveran, A.,and Mesnil, F. Trypanosomes et trypanosomiases. Paris (Masson et Cie.), 1904. An English edition, translated and considerably enlarged and brought up to date by D. Nabarro, has lately been published (London, Bailliére, Tindall and Cox, 1907, 581 pp., 81 text-figg.). 2. Liihe, M. Die im Blute schmarotzenden Protozoen. In Mense’s Handbuch der Tropenkrankheiten, vol. iii. pt. i. (Leipzig, J. A. Barth, 1906), pp. 69- 268, 3 pls., text-figg. 3. Woodcock, H. M. The Haemoflagellates. Q.J. Mier. Sci. 1., 1906, pp. 151-331, 65 text-figg. : LITERATURE OF THE HAEMOFLAGELLATES 269 B. List of the more important memoirs cited in the text. (N.B. Full references to the existing literature are given in each of the above works. ) 4, or “I 12. 13. 14. 15. 16. Le oF ihe 19. 20. 21. 22. 23. 24. Billet, A. Culture d’un Trypanosome de la grenouille chez une Hirudinée : relation autogénique possible de ce Trypanosome avec une Hémogrégarine. C.R. Ac. Sci. cxxxix. p. 574, 1904. . — Sur le Z'rypanosoma inopinatum . .. et sa relation possible avec les Drepanidium. C.R. Soc. Biol. lvii. p. 161, 16 figg., 1904. oo”) . Bradford, J. k., and Plimmer, H. G. The Trypanosoma brucii, the Organism found in Nagana or the Tsetse-fly Disease. (.J. Micr. Sci. xlv. p. 449, 2 pls., 1902. Bruce, D. Reports on the Tsetse-fly Disease or Nagana. Ubombo, Zululand, 1895 and 1896 ; London, 1897 and 1903. , Nabarro, D., and Greig, FE. D. [Reports on Sleeping-Sickness and various Animal Trypanosomoses in Uganda.] Roy. Soc. Comm., 1903-1907. / . Brumpt, E. Contribution a l’étude de l’évolution des Hémogrégarines et des Trypanosomes. C.R. Soc, Biol. lvii. p. 165, 1904. Sur quelques especes nouvelles de Trypanosomes parasites des poissons d’eau douce ; leur mode d’évolution. Op. cit. Ix. p. 160, 1906. Mode de transmission et évolution des Trypanosomes des poissons ; description de quelques espéces de Trypanoplasmes des poissons d’eau douce ; Trypanosome d’un crapaud africain. 7'.c. p. 162, 1906. Expériences relatives au mode de transmission des Trypanosomes et des Trypanoplasmes par les Hirudinées. Op. cit. 1xi. p. 77, 1906. Role pathogene et mode de transmission du Trypanosoma inopinatum, Ed. et Et. Sergent. Mode d’inoculation d’autres Trypanosomes, 7’. p. 167, 1906. : De Vhérédité des infections 4 Trypanosomes et Trypanoplasmes chez les hdtes intermédiares. Op. cit. Ixiii. p. 176, 1907. and Lebailly, C. Description de quelques nouvelles especes de Trypanosomes et d’Hémogrégarines parasites des Téléostéens marins. C.R. Ac. Sci. cxxxix. p. 613, 1904. Buffard, M., and Schneider, G. Le Trypanosome de la Dourine. Arch. Parasitol. iii. p. 124, pls., 1900. Castellani, A. Trypanosoma and Sleeping-Sickness. Reports S.S. Comm. Roy. Soe. i. and ii., 1903. Danilewsky, Recherches sur la parasitologie comparée du sang des oiseaux. Kharkoff, 1888-1889. Zur Parasitologie des Blutes. Biol. Centrlbl. v. p. 529 (1885). Dutton, E. Note on a Trypanosoma occurring in the Blood of Man. Brit. Med. Journ., 1902, ii. p. 881, 1 fig. and Zodd, J. L. First Report of the Trypanosomosis Expedition to Senegambia (1902). Mem. Livpl. Sch. Trop. Med. No. 11, 1903. Franca, C.,and Athias, C. Recherches sur les Trypanosomes des Amphibiens : I. Les Trypanosomes de la Rana esculenta. Arch. Inst. R. Bact., Lisbonne, 1., 1906. Gray, A. C., and Tulloch, F. M. The Multiplication of the 7’rypanosoma gambiense in the Alimentary Canal of Glossina palpalis. Rep. 8.8. Comm. Roy. Soc. No. 6, p. 282, 1 pl., 1905. Gruby. Recherches et observations sur une nouvelle espéece d’ Hématozoaire (Trypanosoma sanguinis). C.R. Ac. Sci. xvii. p. 1184, 1843; and Ann. Sci. Nat. (3), i. p. 105, 7 figg., 1844. 270 25. 26. 27. 28. LITERATURE OF THE HAEMOFLAGELLATES Hanna, W. Trypanosoma in Birds in India. Q.J. Mier. Sci. xlvii. p. 433, 1 pl., 1903. Keysselitz, G. Ueber Trypanophis grobbeni (Trypanosoma g., Poche). Arch. Protistenk. iii. p. 367, 3 figg., 1904. — Generations- und Wirthswechsel von 7’rypanoplasma borreli, Lav. et Mesn. Arch. Protistenk. vii. p. 1, text-figg., 1906. Koch, R. Vorlaiufige Mittheilungen iber die Ergebnisse meiner Forschungs- reise nach Ostafrika. Deutsch. med. Wochenschr., 1905, p. 1865, text-figg. 29. Ueber den bisherigen Verlauf der deutschen Expedition zur Erforsch- ung der Schlafkrankheit in Ostafrika. Op. cit. 1906, Appendix, p. 51; also 1907, p. 49. Schluss-Bericht. Op. cit. 1907, p. 1889. 30. Lankester, E. R. On Undulina, the type of a New Group of Infusoria. Q.J. Mier. Sci. xi. p. 387, 4 figg., 1871. 31. The Sleeping-Sickness. Quart. Rev., July 1904, p. 113, 7 figg. 32. Laveran, A. Sur un nouveau Trypanosome des Bovidés. C.R. Ac. Sci. cxxxiv. p. 512, 1902. / é 33. —-- Au sujet de deux Trypanosomes des Bovidés du Transvaal. Op. cit. exxxv. p. 717, 5 figg., 1902. 34. —— Sur un Trypanosome d’une chouette. C.R. Soc. Biol. lv. p. 528, 2 figg., 1903. 35. —— Contribution 4 étude de Haemamoeba ziemanni. T.c. p. 620, 7 figg., 1903. 36. —— Sur une nouveau Trypanosome d’une grenouille. Op. cit. lvii. p. 158, 2 figg., 1904. 37 and Mesnil, F. Recherches morphologiques et expérimentales sur le Trypanosome des rats, 7’. Zewist (Kent). Ann. Inst. Pasteur, xv. p. 673, 2 pls., 1901. 38. —— and Sur les Flagellés 4 membrane ondulante des poissons (genus Trypanosoma, Gruby, et Zrypanoplasma, n. gen.). O.R. Ac. Sci. exxxiii. p. 670, 1901. 39. and Sur la structure du Trypanosome des grenouilles et sur extension du genre Zrypanosoma, Gruby. C.R. Soc. Biol. liii. p. 678, 3 figg., 1901. 40. and Sur les Hématozoaires des poissons marins. C.R. Ac. Sci. cxxxv. p. 567, 1902. 41. and Sur quelques Protozoaires parasites d’une tortue d’Asie (Damonia reevesii). T.c. p. 609, 14 figg., 1902. 42, and Des Trypanosomes des poissons. Arch. Protistenk. i. p, 475, 15 figg., 1902. 43, and Recherches morphologiques et expérimentales sur le Trypanosome du Nagana ou maladie de la mouche tsé-tsé. Ann. Inst. Pasteur, xvi. p. 1, 13 figg., 1902. 44. and Sur un Trypanosome d’Afrique pathogéne pour les Equidés, T. dimorphon, Dutton et Todd. C.R. Ac. Sci. exxxviii. p. 732, 7 figg., 1904. 45. Lebailly, C. Sur quelques Hémoflagellés des Téléostéens marins. Op, cit. 46. exxxix. p. 576, 1904. Léger, L. Sur la structure et la mode de multiplication des Flagellés du genre LHerpetomonas, Kent. C.R. Ac. Sci. cxxxiv. p. 781, 7 figg., 1902, POM aghast: a’ yh —/ aii i pi mk miler et nse 47. Léger, L. Sur un Flagellé parasite de l Anopheles maculipennis. C.R. Soe. Biol. liv. p. 354, 10 figg., 1902. 48. —— Sur quelques Cercomonadines nouvelles ou peu connues parasites de lintestin des Insectes. Arch. Protistenk. ii. p. 180, 4 figg., 1903. 49. —— Sur la morphologie du Z'rypanoplasma des vairons, et sur la structure et les aflinités des Trypanoplasmes. C.R. Ac. Sci. exxxviii. pp. 834, 856, 5 figg., 1904. 50 Sur les Hémoflagellés du Cobitis barbatula, L. ; Trypanosma barbatulae, n. sp.; et Zrypanoplasma varium, n. sp. C.R. Soe. Biol. lvii. pp. 344, 345, 1904. 51. —— Sur un nouveau Flagellé parasite des Tabanids. 7c, p. 613, 6 figg., 1904. 52. —— Sur les affinités de l’Herpetomonas subulata et la phylogénie des Trypanosomes. T7'.c. p. 615, 1904. 53. —— Sur la presence dun Z'rypanoplasma intestinal chez les poissons. 54, 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67. 68. 69. Op. cit. lviii. p. 511, 1905. Lignieres, J. Contribution a l’étude de la trypanosomose des Equidés Sud-Américains connue sous le nom de Mal de Caderas (7'rypanosoma elmassiant). Rec. Méd. Vét. Bull. et Mém. (8), x. pp. 51, 109, 164, 2 pls., 1903. Lingard, A. A new Species of Trypanosome found in the Blood of Rats (India), ete. J. Trop. Vet. Sci. i. p. 5, 1 pl., 1906. M‘Neal, W. J. On the Life-History of ZT. Jewist and 7. brucii. J. Inf. Diseases, 1., Nov. 1904. Minchin, E. A. On the Occurrence of Encystation in Trypanosoma grayi, Novy, etc. P. Roy. Soc. lxxix. B, p. 35, text-figg., 1907. Investigations on the Development of Trypanosomes in Tsetse-flies, etc, QJ. Micr. Sci. lit. p. 159, 6 pls;,. 1908. , Gray, A. C., and Tulloch, F. M. Glossina palpalis in its Relation to Trypanosoma gambiense and other Trypanosomes, P. Roy. Soe. lxxviii. B, p. 242, 3 pls., 1906. Mitrophanow, —--. Beitrage zur Kenntniss der Himatozoen. Biol. Centrlbl. iii. p. 35, 2 figg., 1883. Novy, F. G. The Trypanosomes of Tsetse-flies. J. Inf. Diseases, iii. p. 394, 3 pls., 1906. and AM‘ Neal, W. J. Onthe Trypanosomes of Birds. Op. cit. ii. p: 206, 11 pls., 1905. and 1904. —, ——, and Torrey, H. N. The Trypanosomes of Mosquitoes and other Insects. Op. cit. iv. p. 223, 7 pls., 1907. Patton, W.S. Preliminary Note on the Life-Cycle of a Species of Herpeto- monas found in Culex pipiens. B.M.J., 1907, ii. (July 13th). Plehn, M. Trypanoplasma cyprini, nu. sp. Arch. Protistenk. ii. p. 175, 1 pl, 1903. Pricolo, A. Le Trypanosome de la souris. Cycle de développement des Try- panosomes chez le foetus. Centralbl. Bakt., Abt. 1, xlii. Orig. p. 231, 1906. Prowazek, SS. Studien tiber Siaugethiertrypanosomen. Arb. kais. Gesundhtsa. xxii. p. 1, 6 pls., 1905. Die Entwickelung von Herpetomonas, einen mit den Trypanosomen verwandten Flagellaten. Op. cit. xx. p. 440, text-figg., 1904. On the Cultivation of Trypanosoma bructi. Op. cit. i. a 272 LITERATURE OF THE HAEMOFLAGELLATES 70. Rabinowitsch, L., and Kempner, W. Beitrage zur Kenntniss der Blutparasiten, speciell der Rattentrypanosomen. Zeitschr. Hyg. xxx. p. 251, 1 pl., 1899. 71. Robertson, M. Notes on Certain Blood-inhabiting Protozoa. Proc. Physic. Soe. Edinb. xvi. p. 232, 2 pls., 1906. Studies on a Trypanosome found in the Alimentary Canal of Pontob- della muricata. Op. cit. xvii. p. 83, 4 pls., 1907. 73. Rogers, L. The Transmission of the 7rypanosoma evansi in India by Horse- flies, etc. Proc. Roy. Soc. Ixviii. p. 163, 1901. Also see B.M.J., 1904, ii. p. 1454. 74. Ross, Rk. Notes on the Parasites of Mosquitoes found in India between 1895 and 1899. Journ. Hyg. vi. p. 101, 1906. 75. Schaudinn, F. Generations- und Wirthswechsel bei Trypanosoma und Spirochacta. Arb. kais. Gesundhtsa: xx. p. 387, text-figg., 1904. 76. Sergent, E. and #. Sur un Trypanosome nouveau parasite de la grenouille verte. C.R. Soc. Biol. lvi. p. 123, 1 fig., 1904. 77 Hémamibes des oiseaux et moustiques. Géneérations alternantés de Schaudinn. Op. cit. lviii. p. 57, 1905. ; 78. Sur des Trypanosomes des chauves-souris. TZ.c. p. 53, 2 figg., 1905. 79. —— Sur un Flagellé nouveau de l’intestin des Culex et des Stegomyia, Herpetomonas algeriense. Op. cit. 1x. p. 291, 1906. 80. Stuhlmann, F. Beitraige zur Kenntniss der Tsetsefliegen (GU. fusca and Gl. tachinoides). Arb. kais. Gesundhtsa. xxvi. p. 83, 4 pls., 1907. 81. Swingle, L. D. Some Studies on Trypanosoma lewisi. Trans. Amer. Mier. Soc. xxvii. p. 111, 1 pl., 1907. 82. Thiroux, Sur un nouveau Trypanosome des oiseaux. C.R. Ac. Sci. exxxix. p. 145, 5 figg., 1904. Recherches morphologiques et expérimentales sur les Trypanosoma paddae. Ann. Inst. Pasteur, xix. p. 65, 1 pl, 1905. 84. —— Recherches... sur 7rypanosoma duttoni, Thiroux. Tc. p. 564, 1 pl., 1905. 85. Voges, O. Malde Caderas. Zeitschr. Hyg. xxxix. p. 323, 1 pl., 1902. 86. Wasielewsky and Senn, G. Beitrage zur Kenntniss der Flagellaten des Rattenblutes. Op. cit. xxxiii. p. 444, 3 pls., 1900. II. Relating to the ‘‘ Leishman-Donovan- Wright” Bodies. 87. Christophers, S. R. Reports on a Parasite found in Persons suffering from Enlargement of the Spleen in India. Sci. Mem. India, Nos. 8, 11, 15, 1904-1905. 88. Donovan, C. Human Piroplasmosis. Lancet, 1904, ii. p. 744, 1 pl. 89. James, S. P. Oriental or Delhi Sore. Sci. Mem. India, No. 13, 1905. 90. Laveran, A., and Mesnil, F. Sur un Protozoaire nouveau (Piroplasma. donovani, Lav. et Mesn.), ete. C.R. Ac. Sci. exxxvii. p. 957, 17 figg. 1903 ; and op. cit. cxxxviii. p. 187, 1904. 91. Leishman, W. On the Possibility of the Occurrence of Trypanosomosis in India. Brit. Med. Journ. 1903, i. p. 1252, 2 figg.; see also op. cit., 1904, i. p. 303. : and Statham. The Development of the Leishman Body in Cultivation. Journ. Army Med. Corps, iv. p. 321, 1 pl. 2 figg., 1905. tle LITERATURE OF THE HAEMOFLAGELLATES 273 93. Patton, W. S. Prelim. Report on the Development of the Leishman- Donovan Body in the Bed-Bug. Sci. Mem. India, No. 27, 1907. 94. Rogers, L. On the Development of Flagellated Organisms .. . from the Spleen Protozoic Parasites of Kala-Azar. Q.J. Mier. Sci. xlviii. p. 367, 1 pl., 1904. Further Work on the Development of the Herpetomonas of Kala- Azar... from the Leishman-Donovan Bodies. Proc. Roy. Soc. lxxvii. B, p- 284, pl. 7, 1906 ; see also Lancet, 1905, i. p. 1484. 96. Ross, R. A New Parasite of Man. Thompson-Yates Lab. Rep. (5), 2, p. 79, 1 pl., 1904. 97. Wright, J. H. Protozoa in a Case of Tropical Ulcer (Delhi Sore). Journ. Med. Research, Boston, x. p. 472, 4 pls., 1903. 95. C. Relating to the Spirochaetae. 98. Certes, 4. Note sur les parasites et les commensaux de l’huitre. Biol. Soc. Zool. France, vii. p. 347, 1 pl., 1882; see also op. cit. xvi. pp. 95 and 130, 1891. 99. Laveran, A., and Mesnil, F. Sur la nature bacterienne du prétendu Trypanosome des huitres, ‘‘ 7.” balbianii. C.R. Soc. Biol. liii. p. 883, 1901. 100. Perrin, W. S. Researches upon the Life- History of ‘* Trypanosoma” balbianiit (Certes). Arch. Protistenkunde, Jena, vii. p. 131, 2 pls., 1906. 101. Krzysztalowicz, F., and Siedlecki, M. Contribution 4 l’étude de la struc- ture et du cycie évolutif de ‘Spirochacta pallida, Schaud. Bull. Ac. Cracovie, 1905, p. 713, 1 pl. 102. Schaudinn, F. Zur Kenntniss der Spirochaeta pallida. Deutsch. med. Wochenschr. No. 42, 1905, p. 1665; see also t.c. p. 1728 (gen. Treponema proposed). 103. —— and Hoffmann, E. Vorlaufiger Bericht ueber das Vorkommen von Spirochaeten in syphilitischen Ktankheitsproducten. Arb. kais. Gesundhtsa. xxii. p. 527, 1905. 18 APPENDIX A.’ CHLAMYDOMYXA. THIs genus is represented by two species. C. labyrinthulotdes was dis- covered by Archer in pools in moorland country in Ireland and described by him in 1875 (1). It has subsequently beén investigated by Geddes (2) in material supplied by Archer ; and by Hieronymus (3), who found it in the Riesengebirge and elsewhere in Germany. (0. mon- tana was first described by Lankester -(5) and obtained by him in Sphagnum swamps in Switzerland, and has since been investigated by Penard (6). Two main phases of the life-history are in many respects well known—a free active stage, with pseudopodia more or less extended, and a (much commoner) encysted stage ; and we now have evidence, though it is still incomplete, of stages of multiplication by fission and of spore- formation. Chlamydomyxa unites in a remarkable manner the holophytic and holozoic modes of nutrition. The protoplasmic body is crowded with chromatophores, by means of which it is able to increase largely in size in the encysted state ; but it is also able, in its active phase, to engulf and to digest animal and vegetable organisms. The body consists of hyaline protoplasm containing nuclei, chromato- phores, and small refracting bodies—the “oat-shaped corpuscles” of Lankester. In the encysted condition it may form a globular mass, measuring, when fully grown, 60-90 p in diameter in C. labyrinthulotdes, the cysts of C. montana being a little smaller. The nuclei (Fig. 1, a, b, and d) vary from 1°5 to 3 win diameter. They are generally evenly distributed through the protoplasm, and they increase in number with its growth. In the large cysts of C. labyrinthulotdes there may be as many as 32 or more ; in C. montana, according to Penard, 100 or more. They contain a nucleolus or group of nucleoli at the centre, and there are indications of a nuclear reticulum at the periphery. Their mode of division is, according to Hieronymus, intermediate between mitosis and amitosis. In life they are usually hidden by the chromato- phores, and thus escaped the notice of the earlier observers. The chromatophores are oval bodies varying in size up to 3 yt (C. mon- tana) and 5°5 p (C. labyrinthuloides, Fig. 1, d). They consist of coloured 1 By J. J. Lister, M.A., F.R.S., Fellow of St. John’s College, Cambridge. 274 APPENDIX 275 and colourless tracts, which are apparently differently distributed in the two species, The colour varies from grass-green to olive-green, yellow, and brown, and is dependent on the presence, in varying proportions, of chlorophyll and of a yellow-brown colouring matter (? diatomin). They | wa eh Sele 0 r % y Fie. 1. Chlamydomyxa labyrinthuloides. a and b, cysts from leaf-cells of Sphagnum, constricted by the characteristic annular bands of the latter, from stained preparations showing the chromato- phores and nuclei, x 620. c, end of a living cyst, treated with weak methylene blue solution. The chromatophores are shaded. The nuclei arenotseen. x 5000. d, nuclei highly magnified ; e, f, living chromatophores; g, chromatophore after treatment with Flemming’s fluid and fuchsin ; h, oat-shaped corpuscles ; e-h x about 10,000. (After Hieronymus.) appear to multiply by binary fission (Fig. 1, f). The absence of a cellulose envelope and of a nucleus, as well as other characters of the chromatophores, prevent their being regarded as symbiotic algae. As a degeneration product, and especially under the influence of bright sunlight, the colouring matter breaks down, producing a red or brown fatty substance (lipochrome) which accumulates in drops in the interior of the cysts, and, 276 APPENDIX by its colour, reveals the presence of Chlamydomyxa when it is present in abundance on the vegetation of a pool. The oat-shaped corpuscles (“spindles” of Archer, ‘‘physodes” of Hieronymus) are shining, highly-refracting bodies, homogeneous or faintly laminated, of a pale bluish tint and semifluid consistence (Fig. 1, h). They are round or oval in shape, but become longer (oat-shaped) when drawn out on the pseudopodial filaments. They vary in size up to about 2 yin length. Asregards composition, Hieronymus identifies them with phloroglucin, a member of the aromatic series which occurs in the Fucaceae. When Chlamydomyxa was discovered the resemblance between these bodies, held in the expanded, stiff pseudopodial network (Fig. 3 (2)) and the nucleated units of the associations of Labyrinthula, suggested the view that they might be of similar nature, although nothing of a nuclear character could be revealed in the corpuscles by stains, and they are, moreover, much smaller than the units of Labyrinthula. The evidence which we now have as to the nuclei of Chlamydomyza, and as to the chemical nature of these bodies, prevents our acceptance of this view. They are probably to be regarded as reserve food material (possibly in relation with the metabolism of cellulose) stored in a granular form. Crystals of oxalate of lime, formed doubtless in the katabolie pro- cesses, are also present in the cell-fluids, and they may be crowded in vacuoles of the encysted animal, to be expelled when it emerges. The cysts of Chlamydomyzxa are found in great abundance within the large cells of the leaves of Sphagnum, or between the cells of other aquatic plants (Hypnum, Eriocaulon, cotton-grass, etc.). They may also be found on the surface of these and other submerged bodies. They are invested by a cellulose envelope, often consisting of several laminae added one within another, and the investment appears to be of a plastic consistency, expanding with growth so as to cover large protrusions of the cyst which extend through apertures in the cell-wall, and it may close in about portions which are withdrawn from deeper recesses of the plant tissue, Considerable growth of the protoplasmic body may occur in the encysted condition, a result dependent on the holophytic nutrition brought about by the agency of the chromatophores. The youngest cysts found in a Sphagnum leaf are very small and contain a single nucleus. As they increase in size and become limited by the walls of the elongated leaf-cells they grow in length (Fig. 1, a and b). The cysts may finally break through the wall of the cell and project in lobate prominences. to the exterior. The activities of the encysted organism do not, however, result in uniform growth, for many cysts have shrunken contents, and have formed a fresh wall separate from the original one, and in the space between the envelopes groups of the red oil-globules referred to above may lie, discharged before the inner wall was secreted. Moreover, the contents of a cyst may undergo division within the envelope into two or more parts, and each part then forms a wall of its own. When the cysts are fully grown and favourable conditions occur, an aperture is formed in the envelope, presumably by the solvent action of the protoplasm on the cellulose, and the contents emerge in the free state. APPENDIX 277 The accounts of the behaviour of the organism in the free state differ considerably and are not easy to reconcile, In OC. labyrinthuloides, as described by Archer (cp. his figure in the Q.J.M.S. vol. xv. Plate vi., from which Fig. 3 (2) is taken), the proto- plasmic body was still partially contained in the cyst. Extending through the aperture, it was produced into a dendriform system of branches, diminishing in thickness. From the ends and sides of the branches filiform hyaline pseudopodia of small but uniform thickness reach far out into the water. The chromatophores are not seen in relation with the filaments, but these are plentifully beset with the oat- shaped corpuscles. The latter are drawn out in the direction of the filament, and slowly travel along it in one direction or the other. The filaments are sparingly branched; whether or not they anastomose, observers are not agreed, They have a “stiff but flexible” (Penard) consistency. Lankester is inclined to regard the filaments as “inert products of the metamorphosis” of the protoplasm, over which a “delicate varnish” of hyaloplasm extends, investing the corpuscles and carrying them along in its flow. Yet the whole system of these remarkable pseudopodia can be rapidly withdrawn into the general mass when the animal is disturbed. Hieronymus describes a peculiar fibrous arrangement of the protoplasm even in the encysted state, which may be in relation with the peculiar characters of the extended filaments (Fig. 1, c. Note the linear arrangement of the oat-shaped corpuscles). Contractile vacuoles abound in the extended protoplasmic body. Their period probably varies with its activity. In C. montana Penard finds it to be very slow. In the active condition Chlamydomyxa is aie to engulf and digest algae, desmids, Peridinidae, etc., and outlying masses of protoplasm may be seen (Fig. 3 (2)) ris about such food-bodies. The accounts of the active phase of C. montana agree, on the whole, with Archer’s observations of OC. labyrinthuloides, except that in the former species the protoplasm, on emerging, completely quits the old cyst- wall and lies free in the water as a mass of constantly changing shape. It may be more or less spherical or drawn out into a ribbon, attaining a length of 300 » (Penard). A definite hyaline ectoplasm is also present. (Cp. the figures of this species given by lLankester, Q.J.M.S. vol. xxxix. Plates xiv. and xv.) In it, moreover, the yellow colouring matter of the chromatophores usually predominates over the green. According to most observers, the free state of the organism would _ appear to end, after lasting at least “several hours,” by the withdrawal of the extended protoplasm and the re-encystment of the whole animal. Hieronymus differs considerably from other observers in his account of the free state. He has also seen the contents emerge from a cyst of C. labyrinthuloides, assume an irregular amoeboid form, and ingest food “auf thierische Weise” ; but it is remarkable that he has never, during the twelve years over which his observations have extended, seen the long filamentary pseudopodia protruded in the manner which has, in both species, attracted attention. The nearest approach to such filaments which he has seen were those of a small specimen suspended free in the aja 3 APPENDIX water and emitting long pseudopodia on all sides (3 ; Plate ii. Fig. 25). After ingesting food the animals were found by Hieronymus to encyst on the surface of plants, and he states that division of the nuclei follows the’ encystment. But in the majority of cases a different process was observed to follow the emergence from the encysted state. The proto- plasm puts out short pseudopodia and divides up forthwith, by successive bipartition or by simultaneous division, into small uninucleate amoebae, the products of division being equal in number to the nuclei contained in the original cyst. The division into the ultimate products is usually complete in a few minutes from the emergence of the protoplasm. The small amoebae so found may creep about and ingest small algae or bacteria before passing into the encysted form. While this is the usual course, Hieronymus describes cases in which the process of division ceased after one or two partitions had occurred, and was followed by a stage of feeding and subsequent encystment. Further evidence of such cases would be desirable, and it seems possible that two separate phases of the life-history may have been here confused; but it is clear that the fission of the multinucleate body into uninucleate products represents a phase of reproduction comparable with that which occurs in many other protozoan life-histories, and of which we had no previous evidence in Chlamydomyza. Spore-Formation.—The process of spore-formation has been most fully observed by Penard in @. montana,! but stages of it have been seen by Archer and Hieronymus in C. labyrinthuloides. The contents of an encysted form are segregated by simultaneous fission into a number (20 to 40) of equal (Fig. 2, a) (?sometimes only sub-equal (Fig. 2, 6)) divisions, These are at first continuous with their neighbours by proto- plasmic strands (3; Plate i. Fig. 7), but later they separate into bodies which become spherical and each secretes a cellulose wall. They are liberated by the opening of the cyst (in a manner not observed). Penard finds that these secondary cysts, or spores (Fig. 2, c), as we may call them, measure in C. montana 18 p in diameter, and that each contains two nuclei lying opposite one another in a meridian of the sphere. In some cases the contents of the spores were found to have emerged as naked masses of protoplasm, containing the chromatophores and refracting corpuscles characteristic of the species. Each acquired a flagellum (or two flagella ?) about equal to the body in length (Fig. 2, d), and for some moments (“ pour quelques instants”) was actively motile. Some of these flagellate bodies appeared to possess one nucleus, others two or even three, and there was an indication of their fusion in pairs (“lorsque les petits flagellates viennent A se rencontrer, ils peuvent se fusionner en un seul,” p. 331). Some continued to show a slow movement for twenty- four hours, but ultimately they died under the cover-slip. It would be premature at present to make any dogmatic statement as 1 It was only for a few days that Penard succeeded in observing this stage in the life-history. It occurred in March, in the neighbourhood of Geneva, 2 Penard’s account of the subsequent history of these bodies is of great interest, but, owing to the sparseness of his material and the rapidity of some of the events, he was unfortunately not able to observe the stages with precision, With this reserve, an outline of his results is here given. = APPENDIX - 279 to the course of the life-history of Chlamydomyxa. The observations of Penard suggest that the flagellulate bodies hatching from the spores ‘are gametes, which proceed to conjugate with one another, though the existence of two nuclei in the spores requires explanation. If this is the case, we have, as in T'richosphaeriwm and many other Protozoa, a life-cycle in which a sexual phase recurs in a series of generations reproducing by fission. With regard to the affinities of Chlamydomyza, we have seen that the resemblance to Labyrinthula turns out to be in part at least misleading, Chlamydomyxa. a, Early stage of spore-formation in C. montana. The contents of a cyst have become divided up into young spores ; b, acyst of C. labyrinthuloides, with mature spores, x 200; c, a single spore of C. montana, showing two nuclei; d, flagellate body hatched from aspore. (a, c, and d after Penard ; b after Archer.) We are unable to agree with Penard that it is allied to the Mycetozoa, for there is no evidence that the protoplasmic masses are plasmodia in the true sense of the term. It appears that the most satisfactory position to assign to it, in the present preliminary stage of our knowledge of life- histories, is as an isolated rhizopod, containing chromatophores, which may be provisionally placed in the neighbourhood of the freshwater forms with filose pseudopodia which, in this work, are included in the Order Gromiidea of the Foraminifera (see p. 283). In the possession of many nuclei it resembles Trichosphacrium among the Rhizopoda Lobosa. LITERATURE. 1. Archer, VW. On Chlamydomyxa labyrinthuloides, nov. gen. et sp., a New Freshwater Sarcodic Organism. Quart. Journ. Micr. Sci. N.S. xy. (1875), p. 107. 280 APPENDIX 2. Geddes, P. Observations on the Resting State of Chlamydomyzxa laby- rinthuloides, Archer. Ibid. xxii. (1882), p. 30. 3. Hieronymus, G. Zur Kenntniss von Chlamydomyxa labyrinthuloides, Archer. Hedwigia, Bd. xxxvii. (1898), p. 1. 4. Jenkinson, J. W. Abstract and Review of the above paper by Hieronymus. Quart. Journ. Micr. Sci. N.S. xlii. (1899), p. 89. . Lankester, E. Ray. Chlamydomyxa montana, n. sp., one of the Protozoa Gymnomyxa. Quart. Journ. Micr. Sci. xxxix. (1896), p. 233. 6. Penard, E. Etude sur la Chlamydomyxa montana. Arch. f. Protistenkunde, Bd. iv. Heft 2 (1904), p. 296. [| LABYRINTHULA. The members of this genus consist of associations of nucleated proto- ‘plasmic units (“ amoebae” of Zopf, “spindles” of Cienkowski) joined in a network of sparingly branched and anastomosing threads. They are met with in a diffuse or aggregated condition, and, as the result of drying, the units pass into a condition of encystment, from which they hatch out in the form of the amoeboid units. Two marine species were described in 1867 by Cienkowski (1), who found them on algae growing on wooden piles in the harbour of Odessa: L. vitellina, Cienk., in which the protoplasmic units contain a yellow or orange colouring matter ; and L. macrocystis, Cienk., in which the units are larger and colourless. - Zopf (4) in 1892 described a freshwater form very similar to L. macrocystis, parasitic on the alga Vawcheria. He named it L. cienkowskii, Zopf. In the marine forms the system of connecting threads appears to have a remarkably firm and rigid consistency, and Cienkowski describes the movement of the units along the threads, as though the latter were peculiarly differentiated structures ; but from Zopf’s description of L. cienkowskit it can hardly be doubted that they are pseudopodial in nature. Zopf observed them to be slowly protruded from a mass of units, and to be withdrawn, to move slowly from side to side, and to fuse with their neighbours. He also describes the passage of food-granules along them. The units are without a limiting membrane and contain a single nucleus, with a nucleolus. When drawn out in the expanded condition of the organism they are generally spindle-shaped (Fig. 3 (3)), but they may present processes in three directions (Fig. 3 (4)). In the aggregated condition the units are round or oval. Those of ZL. macrocystis measure 18-25 pw in long diameter, those of L. vitellina and L. cienkowskit about 12. The protoplasm is granular, and in L. vitellina contains a yellow or orange fatty pigment, soluble in alcohol. A small vacuole is usually present, but it is not stated that it is contractile. The whole organism, or a part of it, is often found in the aggregated condition (Fig. 3 (5)), and the marine species may thus form masses measuring a millimetre or so in diameter. The main aggregate is described by Cienkowski as invested, in JL. vitellina, by a “cortical sub- stance” (neither protoplasmic nor of the nature of cellulose) through APPENDIX 281 which the filaments are protruded, but this was not seen in the peripheral aggregates of this species, nor at all in the active condition of the other species, Labyrinthula is actively parasitic on the algae which it infests, breaking down the contents of the cells into a granular mass. As the result of drying, the organism passes into a condition of encystment. The units became closely aggregated and each secretes a cyst- wall, which is double in L. ctenkowskit. A firm common envelope may now be formed (in L. macrocystis, Fig. 3 (5), but not in other species) in which the encysted units are embedded. The behaviour of the encysted unit appears to vary in the different species. In L. cienkowskii Zopf describes and figures the emergence of a single mass from the cyst. In the other species, Cienkowski found that the contents divided into four within the cyst (Fig. 3(6 and 7)). Zopf observed . the protrusion of one or two long pointed pseudopodia, on hatching, and the final emergence of the protoplasmic mass from the cyst, which was left empty. From the fact that on one occasion three empty cases were found with three units in their neighbourhood, and that these were in connection by their pseudopodia, Zopf concludes that the hatched units join with one another to start a fresh association. Zopf regards the association of units of Labyrinthula as representing a stage in the formation of a plasmodium intermediate between the true plasmodium of the Euplasmodida (cf. p. 43), in which there is a complete fusion between thé protoplasmic bodies of the uniting amoebulae, and the pseudoplasmodium of the Sorophora, in which the amoebulae, aggregating before spore-formation, come into apposition but maintain their distinct- ness (p. 60). This intermediate form he would distinguish as a Thread- plasmodium (Fadenplasmodium). The propriety of this view seems far from clear. We are familiar with many cases among Protozoa in which an association of individuals, a colonial organism, is formed by the successive multiplication of the units, whose offspring remain in connection by protoplasmic processes (Colonial Radiolaria, Volvox, Mvikrogromia), and the higher animals and plants are often regarded as such colonial organisms, in modified forms. That an increase in the number of units in the associations of Laby- rinthula occurs by binary fission of the units is abundantly clear. It is true that it appears probable, from Zopf’s observation above quoted, that a fusion may occur in Labyrinthula (though it was not actually observed) between the pseudopodia of individuals recently emerged from the encysted state; but a parallel to this process may be found in the fusion of the protoplasmic masses emerging from the cysts of the sclerotial condition of the Mycetozoa on revival of activity (cp. p. 50). There are fair grounds for regarding the fusion of the amoebulae by which the Mycetozoan plasmodium takes its origin (in the Euplas- modida) as a part, at any rate the plastogamic part, of a sexual union of which the final, karyogamic, stage is deferred. It would not be sug- gested that the fusion after the sclerotial stage is a repetition of this process in the Mycetozoa, and we may well hesitate, in the present 282 L | ae APPENDIX 283 fragmentary state of our knowledge of Labyrinthula, to.accept the conclu- sion that the (inferred) fusion between the pseudopodia after encystment represents this important event in its life-history. We are therefore inclined to regard Labyrinthula as a colonial organism of which the units remain in connection by their pseudopodia. As the result of drying they may pass into the encysted stage, in which they are isolated from their fellows by the cyst-walls. It appears prob- able, from Zopf’s observation, that, on resuming activity, they may again unite with their fellows to form acolony, Other stages of the life-history are at present unknown to us. With Labyrinthula Zopf associates the genus Dzplophirys (Archer), Cienk. The species named Dziplophrys stercorea by Cienkowski (2) is a colonial organism, with simple thread-like pseudopodia, living on horse- dung. It can hardly belong to the same genus as Dzplophrys Archeri (Barker), with ramifying pseudopodia and a distinct though membranous Fic. 3. 2. Chlamydomyxa labyrinthuloides, Archer. The animal in the free state partially emerged from the many-layered cyst. A small encysted mass is seen at ¢ between the envelopes of the latter. Ato and elsewhere in the main body of the protoplasm, as well as in outlying portions, ingested food particles are shown. The oat-shaped corpuscles are seen on the stiff extended filaments. x about 150. (From Lankester, after Archer.) 1 and 3, Labyrinthula vitellina, Cienk. 1, a colony crawling upon an alga. The units are partly aggregated, partly extended on the network of stiff extended pseudopodia. x about 120. 3, part of the network, x about 250. . +73 19 290 INDEX Doflein, F., 13 Donovan, 256, 272 Dopter, 82, 92 Dorataspidae, 146 Dorataspis, 127 Dourine, 196, 197, 206 Dreyer, 116, 131, 152 Dum-dum fever, 256 Durham, H., 240 Dutton, 196, 255, 269 Echinomma 145 Echinostelium, 63 Ectobiella, 3 f., 12 Ehrenberg, 17, 112, 151, 155 Eikenia, 80 Elaeorhanis, 14, 22, 23, 34 Elaster, 35 Elpatiewsky, W., 93 x. Enchylema, 69 Endamoeba, 68, 71, 82; E. blattae, 74 f., 83, 84 f.; #. coli, 73, 74, 75, 82 f. ; E. histolytica, 75, 82, 837. ; £. wurai, 83; £. undulans, 83 Endosporeae, 40, 57 Endyonema, 2, 3, 5, 12 Enerthenema, 62 Engler, 191 Enteridium, 63 Enteromyxa, 3, 12 Entocannula hirsuta, 148 Entosiphon, 171 Esox lucius, 255 Estrella, 33 Eucecryphalus, 128 Eucoronis nephrospy7ris, 146 Eucyrtidium, 127; 4£. crantoides, 108 f. Eudorina, 181, 182 Euglena, 157, 161, 171; leptoderinum, FE. acus, 166 f.; £. gracilis, 172; E. viridis, 166 f., 172 Euglenina, 171 Euglenoidea, 170 Euglenopsis, 171 Eu-mycetozoa, 39 Euplasmodida, 39, 40, 43 Euphysetta nathorsti, 148 Eutreptia, 171 Evans, G., 195 Exosporeae, 40, 57, 64 Exuviaella, 185; marina, 127 E. Famintzin, 58, 66, 98, 129, 152 **Fingersand Toes’”’ disease, Flagellata (Mastigophora), 155 flagellulae, 4, 5, 29 Flowers of Tan, 47 Forde, 196 Fowler, 113, 152 Fran¢a, 254, 269 Frenzel, 91 Frenzelina, $0 Fuligo, 50, 55, 56, 57, 62, 65; F. septica, 40 f, af, a7 J Gamble, 22, 35, 99, 110, 129, 153, 180, 192 Gametocytes, 25 Gasteromycetes, 40 Gazelletta, 149 Geddes, 274, 280 Giemsa, 196 Glaeocystis, 180 Glenodiniidae, 186 Glenodinium cinctum, 184 SJ. 3 G. pulvisculus, 187 Gloidium, 2, 3, 5, 6 /f. Glossina, 200; G. fusca, 199 n., 200, 201; G. morsitans, 199; G. palli- dipes, 199 n.; G. pal- palis, 199, 200, 231; G. _ tachinoides, 200 Gluge, 195 Goebel, 13 Goés, 284, 286 Goldschmidt, R., 91, 163, 164, 192 Golenkinia, 33, 179 Gomphonema, 7 Gonium, 158, 182; G. pectorale, 158, 166 f. Gonyaulax, 187 — Grassia, 164 Gymnosphaera, 23, 33 Gyromonas, 169 Hicker, 113, 117, 122, 153 Haeckel, 1, 13, 104, 110, 119, 127, 131, 152, 284 Haeckelina, 8 Haematococcus, 180; palustris, 166 f. Haematomonas, 250 Haematopinus, 198, 203 Haematopota, 242, 258 Haemoflagellates, 193 ; bio- logical considerations, 217 ; classification, 248 ; comparative morphology, Ht. 207; evolution and phylogeny, 240 ; habitat, 196; historical, 194; Leishman - Donovan - Wright bodies, 255 ; life- cycle, 226 ; list of hosts, 162; literature, 268°; multiplication, 222 Halistemma _ tergestinum, 249 Halteridium, 236, 248 Hanburies, 3 Hanna, 270 Haplococcus, 3, 12 Harper, 65 Hartmann, 159 n., 192 Hartog, E., 13, 68 Hedriocystis, 23. 34 Helcosoma tropicum, 259 Heleopera, 85, 90 Heliophrys, 33 Heliosphaera inermis, 103 f. Heliozoa, 14; classification, 33; food, 18; karyo- kinesis, 25; literature, 385; nucleus, 25; re- production, 28; skeletal investments, 233; struc- ture, 15 Gray, 199, 200, 203, 230, | Hemiclepsis, 227 269 Greeff, 22, 24 Greenwood, 49, 66 Greig, 199 Grenacher, 23, 28, 35 Gruber, 78 Gruby, 269 Gubernaculum, 159, 194 Gulttulina, 60, 65 Guttulinaceae, 65 Gymnamoebida, 77 Gymnococcus, 3, 5, 11 Gymnodinium, 183, 184 Gymnophrys, 2, 3, 9; G. cometa, 10 f. Hemidinium, 183, 184 Hemitrichia, 55, 64; H. chrysospora, 56 f. Hérouard, 39 Herpetomonas, 157, 161, 226, 240, 241, 250; H. biitschlti, 245 n; H. bombycis, 245 ; H. eulicis, 242; H. gracilis, 241, 245; H. jaculum, 241; H. lewisit, 195; H. minuta, 241; H. muscae- domesticae, 232, 241; H. sarcophagae, 245 ; H. subulata, 241 f. Hertwig, on Heliozoa, 15, 24 fi, 25, 27,. 81, 82, 35; on Lobosa, 75, 87, 91; on Radiolaria, 114, 115, 123, 127, 152 Heterodermaceae, 63 LHeterodinium, 187 Heteromastigina, 248 Heteromastigoda, 167 heteromastigote, 158 Heterophrys, 21, 22, 28, 34, 164; H. Fockei, 24 J.; H. myriopoda, 16 f., 23 THexacontium enthacan- thium, 145; H. pachy- dermum, 145 Hexaconus, 146 TTexadoras borealis, 145 Hexalaspidae, 146 Hexalonche philosophica, 145 Hexamitus, 157, 162, 169; H. inflatus, 178 f.; H. muris, 170 Hexaplagia arctica, 147 Hickson, 162, 192, 194 n: Hieronymus, 274, 276, 280 Hinde, 153 hip-paraplegia, 206 Hippobosca rufipes, 199 f. Hirmidium, 158, 177 Histioneis, 188; H. cym- balaria, 184 f. Hoffmann, 273 Holmes, 206 7. Holomastigoda, 164 holomastigote, 158 Holopsamma, 286 Homokaryota, 68 Hoogenraad, 13 Hosts of Haemoflagellates, list of, 262-268 Huxley, 151 Hyalobryon, 157, 158, 174 Hyalodiscus, 80 Hyalolampe, 34 Hydnum, 40 Hydrochoerus 252 Hydrodictyon, 179 Hydrurus, 176 Hymenomonas, 161, 176 hypnocysts, 4 hypothallus, 54 capybara, Idiochromidia, 71 Ijima, 91 Immermann, 110, 153 Ineffigiata, 179 isomastigote, 158 INDEX Jahn, 42, 65, 66 James, 272 Jenkinson, 280 Jennings, 70, 91 Johnstone, 129, 153 Jiirgens, 92 Kala-Azar, 256 Karawiew, 123, 152 Karyokinesis, in Actino- sphaerium, 25; in Lobosa, 73; in Mastigophora, 161 (Noctiluca, 190); in Mycetozoa, 46/7, 48, 65; in Proteomyxa, 2; in Radiolaria, 126; in a Trypanosome, 213 Keeble, 22, 35, 99, 110, 129, 153, 180, 192 Kempner, 198, 272 Kent, 195 Keuten, 172 Keysselitz, 198, 229, 270 Klebahn, 35 Klebs, 127, 153, 161, 165, 172 Koeh,. 200, 203, 251 a, 270 Kofoid, 182, 187, 192 Krinzlin, 65 Krohn, 188 7. Krukenberg, 50, 66 Krzysztalowicz, 273 Labyrinthula, 39, 276, 280; LZ. ctenkowskii, 280; L. macrocystis, 280, 282 f. ; L. vitellina, 129, 280, 282 /. Labyrinthuleae, 39 Lachnobolus, 64 Lamnblia intestinalis, 170 Lampoxanthium murray- anum, 144 Lamproderma, 62 Lamprosporales, 63 Lang, A., 13 Lankester, on Chlamy- domyxa, 274, 277, 280 ; on Haemoflagellates, 195, 270; on Heliozoa, 17, 36; on Labyrinthula, 283; on Lobosa, 80; on Mastigophora, 158 7., 162, 168 n. ; on Myce- tozoa, 67 ; on Radiolaria, 152 Larcoidea, 145 Laveran, 196, 204, 206 n., 207, 28 ~21.,5 246, 252, 268,270,272, 273 291 Lebailly, 270 Lecquereusia, 89; L. spiralis, 89 f. Leeuwenhoek, 155 Léger, 196, 198, 215, 217 n., 226, 229, 2380, 234, 240, 242, 245, 247, 257 n., 258, 270, 271 Leidy, 23 Leishman, 196, 257, 272 Leishmania donovani, 232, 256, 257 f. ; L. tropica, 257 f., 259 Leishman- Donovan- Wright bodies, 255 Leocarpus, 62 Lepidoderma, 56, 62; L. tigrinuum, 54 fF. Lepocinelis, 171 Leptodiscus, 190 Leptomonas, 165 Leptophrys, 2, 3,4 f., 5, 8 Lesage, 82, 92 Lesser, 15, 24 f. Lethodiscus mMicroporus, 145 Leuciscus erythrophthal- mus, 249 Lewis, 195 Leyden, 91 Leydenia, 84; L. gemmi- para, 84 Licea, 63; L. pusilla, 56 Liceaceae, 63 Lieberkiihn, 84 Life-history of Chlamy- domyxa, 274; of Haemo- flagellates, 226 ; of Helio- zoa, 15; of Lobosa, 75; of Mastigophora, 155, 162, 164, 172, 180, 189 ; of Mycetozoa, 40, 58, 59; of Proteomyxa, 3; of Radiolaria, 104, 111 Ligniéres, 218 n., 219, 271 lime-knots, 55 Lindbladia, 63 Lingard, 271 Lingbya, 2, 8 linin, 18 Lister, A., 61, 67 Literature, of Chlamydo- myxa, 279; of Hemofla- gellates, 268 ; of Heliozoa, 35; of Labyrinthula, 283; of Lobosa, 91; of Mastigophora, 191; of Mycetozoa, 66; of Pro- teomyxa, 13; of Radio- laria, 151 ; of Xenophyo- phoridae, 286 292 Lithamoeba, 80; L. discus, 80 /f. Lithelius arborescens, 145 ; LI. minor, 145 Lithocireus annularis, 105 fs 146 Lithocolla, 34 Lithogromia silicea, 148 Litholophus, 111 Lithomelissa setosa, 147; L. thoracites, 147 Lithosphauerella, 34 Lobosa, 68 ; chromidia, 71 ; classification, 77 ; litera- ture, 91; nucleus, 70; reproduction, 72 Lohmann, 174, 192 Lophomonadina, 170 Lophomonas Oblattarum, 178 f. Lotsy, 192 Liihe, 245, 247, 268 Lycogala, 56, 64 Lycogalaceae, 64 Mallomonas, 161, 176 Margarita, 64 Margaritaceae, 64 Martini, 91 Mastigamoeba, 160, 164; M, schulzei, 164 Mastigella, 156, 163, 164, 177; M. vitraea, 159 f., 164 f7.; M. vitrina, 164 Mastigina, 160, 164; M. setosa, 164 Mastigophora, 11, 155; classification, 163 ; habit, 157; literature, 191; nucleus, 161; nutrition, 157 ; structure, 158 Maupas, 20 Maupasia, 159, 170 Mayer, 195 M‘Neal, 217, 218 n., 223, 227, 240, 242, 244, 245, 253, 271 Medusetta tiara, 148 Medusettidae, 148 Megastoma, 157, 169; M. entericum, 169 Menoidium, 171 Mereschkowsky, 13 Mesenterica, 44 Mesnil, 91, 196, 204, 206, 207, 218 n., 245, 252, 272, 273 Mesoscena, 114 Metschnikoff, 50, 67 microcysts, 42 Microglena, 161, 176 INDEX Mikrogromia, 39, 281 Minchin, 159 v., 192, 196, 199, 200, 201, 203 x., 230, 231, 233, 246, 271 Mitrophanow, 195, 271 Monadina, 38, 248 Monadineae, 5, 6 2. Monadopsis, 8 Monas, 166, 167 Monera, 1 Monobia, 3, 5 f., 6, 15 Monocercomonas, 169 Monolabis, 22 Monomastigoda, 165 Monomastigote, 158 Monomastix, 159, 170 Monophyes gracilis, 249 Monopodium, 8 Monopylaria, 103, 107 Monostomatina, 169 Monticelli, 13 Moore, 159 n., 192, 206 x. Mucorinae, 40 Mugliston, T. C., 93 Miiller, Johannes, 131, 151 Multicilia, 160, 163, 164; M, lacustris, 164 Murray, J., 13, 113, 192 Murrayella, 187 Musgrave, W. E., 93 Mycetozoa, 37 ; classifica- tion, 61; life-cycle, 42 ; literature, 66 Myzastrum, 3, 5, 8 Myzxodictyum, 11 Myzodiscus crystalligerus, 33 Myzxosphaera coerulea, 140 Nabarro, 199, 252 Nadinella, 90 Nagana, 195, 197, 198 Nassellaria, 107, 113, 114 Nationaletta, 149 Nawaschin, 11, 13 Nebela, 85, 87, 90 nebenkérper, 70 Nepveu, 196 Neresheimer, 71, 91 Neusina agassizii, 284 Noctiluca, 162, 188, 190; N. miliaris, 161 f., 189 fey LOO Tr, hOGA). Novy, 200 n., 217, 218 x., 227, 239, 240, 242, 244, 245, 253, 271 Nuclearia, 8, 9, 14, 15, 23, 33; WV. delicatula, 10 /. Nuclei in Chlamydomyxa, 274; in Haemoflagellates, 194, 212; in Heliozoa, 18 ; in Actinosphaerium, 25, 32; in Labyrinthula, 280 ; in Lobosa, 70, 86 ; in Mastigophora, 161 ; in Mycetozoa, 48, 59; in Proteomyxa, 2 ; in Radio- laria, 94, 107, 110, 120 Oat-shaped corpuscles, 39, 274 Ochromonas, 157, 174 Oedogonium, 8 Oicomonas, 157, 165; O. mutabilis, 166 f.; O. termo, 166 /f. Oligonema, 64 Olive, 60, 66, 67 Orcadella, 63 Ornithocercus, 186, 187; O. magnificus, 184 f. Orosphaera, 122, 144 Orosphaeridae, 144 Ostenfeld, 36 Ouramoeba, 78 f., 79 Oxyrrhis, 163 n., 168, 184 f. Oxytoxum, 187 Palmella, 180 Palmella stage in Zoo- xanthellae, 98 ; in Flagel- lates, 156 Palmodactylon, 180 ‘| Palmodictyon, 180 Pandorina, 182 Pantostomatina, 164 Paramastigoda, 167 paramastigote, 158 Paramecium, 20; P. cos- tatum, 195; P. lorica- tum, 195 Paramoeba, 19; P. eilhardi, 70 f., 73, 75, 79) Gas P. hominis, 79, 83 Paramoecoides, 250 Paranema, 171; P. tricho- phorum, 166 f. Paranemina, 171 Parmulina, 89 Patton, 242, 259, 271, 273 Pediastrum, 179 Pelomyxa, 2, 68, 70 7, 71, 73, 75, 76 f., Sia palustris, 72 f., 76 f, 81 f/.; P. penardi, 81; P. villosa, 81; P. viridis, 81 Penard, E., 13, 22, 23, 33, 36, 39, 67, 91, 274, 277, 278, 280 Penardia, 3, 9 Perichaena, 64 Peridiniaceae, 185 | Peridinium, 186 187; P. divergens, 186 //. Peripylaria, 102 Perrin, 273 Petalomonas, 171 Phaeoconchia, 150 Phaeocystina, 147 Phaeodaria, 108, 113 Phaeogromia, 148 Phaeosphaera, 176 Phaeosphaeria, 148 Phalacroma, 188 Phalansteriina, 177 Phalansterium, 158, 163 ., 177; P. consociatum, 166 J.; P. volvocis, 168 Pharyngella gastrula, 148 Phormobotrys hexathalomia, 147 Phorticium pylonium, 145 Phractopeltidae, 146 Phryganella, 90 Phyllomitus, 167 Phyllomonas, 167 Phyllostaurus, quadrifolius, 146 Physaraceae, 56, 62 Physarella, 62 Physarum, 52 n., 55, 62; P. mutans, 54 f. Physematiidae, 104, 144 Physematium, 121; P. miillert, 144 Physomonas, 167 Phythelius, 33 Phytoflagellata, 177 Pinaciophora, 24, 34 Pinacocystis, 21, 24, 34 Piroplasma, 256; P. dono- vani, 243, 257 f., 259 Plagiacantha avrachnoides, 147 Plagiocarpa procyrtella, 147 Plagoniscus _ tripodiscus, 107 /. Planktonetta atlantica, 120/., 1497. Plasmodiocarps, 56 Plasmodiophora, 2, 3, 4 2., 5, 11 Plasmodium, in Labyrin- thula, 282; in Lobosa, 72; in Mycetozoa, 43, 57 ; in Proteomyxa,3 plasson, 2 plastogamic fusion, in Heliozoa, 19; in Lobosa, 88 146; P..- INDEX Plate, 190 Platnaspis, 146 Platoum, 90 Platydorina, 158, 182; P. caudata, 182//. Platytheca, 167 Plectellaria, 147 Plectoidea, 147 Plectophora arachnoides, 147 ; P. novena, 147 Plehn, 271 Plenge, 42, 67 Pleodorina, 181, 182; P. illinoisensis, 183. Pleurococcus, 179 Plewromonas, 167 Plimmer, 206 n., 269 Podolampas, 187 Polykrikos, 185 Polymastigina, 169 polymastigote, 158 Polyoeca, 177 Polyplagia novenaria, 147 Polyporus, 40 Polysphondylium, 60, 65; P. violaceum, 60/. Polytoma, 177 ; P. weella, LSJ. Pompholyxophrys, 22, 24, 34 Pontigulasia, 89 ; P. incisa, Soe Pontobdella, 204, 224, 228 Pontomyxa, 9; P. flava, 9; P. pallida, 9 Pontosphaera, 176; P. haeckelit, 175 f. Popowsky, 136, 153 Porocapsa, 146; P. mur- rayand, 146 Porospathidae, 148 Poteat, W., 91 293 Protogenes, 5, 9; P. prim- ordialis, 9f. Protomastigina, 165 Protomonas, 11, 60; P. amyli, 38; P. parasitica, 38 Protomyxa, 3, 4, 7 f., 11; P. parasitica, 10 f. Prototrichia, 64 von Prowazek, on Haemo- flagellates, 198, 205, 212, 225,50 229; 20 May ay 257 n., 271; on Helio- zoa, 35; on Mastigo- phora, 159 n., 163, 192 ; on Proteomyxa, 4%. Prunocarpus datura, 145 Prunoidea, 145 Prunophracta, 146 Psammetta, 286 Psammina — globigerina, 285 f. Psamminidae, 286 Psanvnopemma, 286 Pseudamphimonas, 11, 12 Pseudochlamys, 89 Pseudodifiiugia, 90 Pseudopodia, of Heliozoa, 23; of Lobosa, 85; of Mastigophora, 160; of Proteomyxa, 3; of Radio- laria, 96, 106 Pseudospora, 3, 5, 8, 163 Pseudosporidium, 10, 12 Ptychodiscidae, 187 Ptychodiscus nocticula, 187 pulsellum, 158 2. Piitter, 98, 153 Pyramidomonas (= Pyra- mimonas), 179, 180 Pyrophacus, 187 Pyzxidicula, 91 Poteriodendron, 158, 161,| Quadrula, 84, 85, 89; Q. 168 Pouchetia, 185 Prantl, 192 Pricolo, 171 Proales, 23 Prorocentraceae, 185 Protanoeba, 2, 5, 6 Proteomyxa, 1 Proterospongia, 158, 177; P. haeckelii, 178 f. Protobathybius, 12 Protoceratium, 187 Protococcus, 180 irregularis, 84 Quatrefages, 189 Rabinowitsch, 198, 272 Radiolaria, 94 ; bionomics, 96 ; central capsule, 114 ; classification, 144 ; cyto- plasm, 116 ; distribution, 112; food, 97; literature, 151; nucleus, 120 ; repro- duction, 136; skeleton, 130 ; variation in, 110; yellow cells, 126 Protocystis harstont, 148 ;| Raphidomonas, 174 P. tridens, 148 ; P. tri- | Remak, 195 tonis, 148 ; P. xiphodon, | Reproduction, in Chlamy- 148 domyxa, 275; in Hae- 294 moflagellates, 222; in Heliozoa, 19, 28; in Lobosa, 72; in Masti- gophora, 156; in My- cetozoa, 41; in Proteo- myxa, 4; in Radiolaria, 99, 136 Reticularia, 52 n., 56, 64; R. lycoperdon, 42°. Reticulariaceae, 63 rhabdoliths, 174 Rhabdomonas, 171 Rhabdosphaera, 176 Rhaphidiophrys, 22, 24, 28, 34; R. elegans, 35/.; R.. paltida; 16 f.; HR. viridis, 22, 23 Rhaphidocystis, 24, 34 Rhipidodendron, 158, 168 Rhizomastigoda, 164 Rhizoplasma, 9 Rhizoplegma boreale, 145 Rhumbler, 5, 6 x., 13, 70, 85, 91 Rhynchomonas, 168 Robertson, 163, 169, 192, 204, 214 n., 216 x., 224, 228, 229, 272 Rogers, 226, 257, 272, 273 Romanowsky, 196 Roubaud, 203 x., 231 a. Ross, 240, 242, 272 Ruppia, 3 Sagena ternaria, 148 Sagenoarium, 148 Sagosphaera trigonilla, 148 Sagosphaeridae, 148 Sulpingoeca, 161, 177; 8. Jusiformis, 178 f.; 8. urceolata, 178 f. Saltonella, 80 Saunders, 49 Schaudinn, on Haemofla- gellates, 196, 198, 202, 205, 212, 217, 226, 235, 241 n., 248 n., 258, 272, 273; on Heliozoa, 27, 29, -82,;° 34,36; on Lobosa, 70, 75, 87, 88, 92; on Mastigophora, 163, 192; on Proteo- myxa, 6 2. ; on Radio- laria, 153 Scheel, 74, 92 Schewiakoff, 118, 131, 153 Schizochlamys, 180 Schizogenes, 12 Schleimeysten, 232 Schleppgeissel, 194, 218 INDEX Schneider, 5 7, 13, 31, 32, 205, 269 Schroder, 122, 153 Schuberg, A., 92 Schubotz, 92 Schultze, 285, 286 Schiitt, 187, 192 Sclerotium, 44, 50 Scyphosphaera, 176; S. apsteini, 175 /f. Scytomonas, 171 Selenastrum, 179 Senn, 192, 212, 272 Sergent, 196, 226, 272 Siedlecki, 273 Siphonosphaera, 121, 123 Siphoptychium, 63 Smith, 31, 36 Sorokin, 13 Sorophora, 39, 59, 65 Sphaerastrum, 28, 34 Sphaerella, 179, 180; S. palustris, 166 f. Sphaerellaria, 106, 113, 114 Sphaerocapsa, 146; S. cruciata, 146 Sphaerocapsidae, 146 Sphaerocystis, 180; S. Schroteri, 22 Sphaeroeca, 158, 177 Sphaeroidea, 145 Sphaerophracta, 146 Sphaeropylidea, 145 Sphaerozoa, 102, 104, 145 | Sphaerozoidae, 104, 145 _ Sphaerozoum neapolitanum, 138, 141 /.; S. ovedimare, 145 Sphenomonas, 171 Spirilla, 195 Spirochaeta evansi, 195 Spirodinium, 183, 185 Spirogyra, 7, 8, 32 Spiroidea, 147 Spironema, 170 Spirula, 11 Spongodiscus favus, 145 Spongomonas, 168 Spongosphaera streptacan- tha, 105 f. Sporangia, 50 Spores in Mycetozoa, 53 ; in Proteomyxa, 4 Sporophore, 58 Spumaria, 56, 57, 62; S. alba, 54 f. Spumellaria, 113 Staborgan, 188 Stahl, 61, 67 Slannarium, 286 _Syracosphaerinae, 176 Stannoma, 284, 286 Stannomida, 286 Stannophyllum, 284, 286 ; S. zonarium, 284 f. Statham, 257, 272 Steel, 195 Stegomyia, 240 Steiniella, 187 Stemonitaceae, 53, 62 Stemonitis, 62; S. ferru- ginea, 55 f.; S. fusca, 41 7., 57; S. splendens, 55 f. Stephanosphaera, 158, 182 Stephoidea, 147 Stereum, 49 Sterromonas, 167 Stichogloea, 176 Stolé, A., 92 Stomoxys calcitrans, 199 f. Strasburger, 52 n., 67 Streptomonas, 168 Stuhlmann, 200, 203, 216, 230, 231, 272 Stylamoeba, 80 Stylochrysalis, 157, 163 n., 174 Swingle, 225 n., 272 Symbiotic Algae (Peridin- ians), 94 Syncrypta, 173, 176; S. volvox, 166 f. Synura, 157, 161, 176 Syracosphaera, 176 Tabanus, 242; T. lineola, 199 f. Tansley, 180, 192 Tanypus, 245 Tetramitus, 157, 169; T. rostratus, 178 f. ; T. sul- catus, 178 f. Tetramyxa, 2, 3,11 Tetraspora, 180 Thalassicolla, 94, 113, 114, 123; 7. pelagica, 95 f. 5 T. pellucida, 144; T. nucleata, 98, 99, 101 f,, 103 f.,,144; 7. spumida, 144 Thalassicollidae, 104, 144 Thalassiosolen atlanticus, 144 Thalassolampe, 121; T. margarodes, 144 Thalassophysa, 120; papillosa, 144; T. pela- gica, sanguinolenta, 128 fi, To. 24 138 f., 144; 7. spicu- losa, 138 /. Thalassophysidae, 104, 144 | Zrypanosoma, Thalassothamnidae, 144 Thalassothamnus, 122 /f.; T. ramosus, 144 Thecamoebida, 68, 84 Theoconus ariadnes, 147 Thiroux, 218 n., 239, 272 Thread-plasmodium, 39, 281 Todd, 255 Topfer, 237 n. Topsent, 13 Torrey, 237 n. Trachelomonas, 161, 171 tractellum, 158 x. Trepomonas, 169 Trepospyris corliniscus, 107 f. Trichamphora, 62 Trichia, 52 n., 64; T. Jollam, 52 »., 58; T. varia, 53 f., 567 Trichiaceae, 44, 55, 64 Trichomastix, 157, 169 Trichomonas, 157, 160, 162,169 ; 7. intestinalis, 169 Trichosphaertum, 22, 68, 72,12; (5, 80, 102, 127 Tridictyopus, 115; T. ele- gans, 147 Trigonomonas, 169 Trimastigina, 169 Trimastix, 169 Triposolema, 188 Tripylaria, 102, 108, 147 Trochiscia, 179 Trochodiscus echiniscus, 145 ; 7. heliodes, 145 Trophochromidia, 71 Trophonucleus, 214 Tropidoscyphus, 171 Truncatulina, 112 Trypanomonas, 250 Trypanomorpha, 167, 198, 238, 248 Trypanomorphidae, 167, 248 Trypanophis, 168, 209, 211, 213, 216, 249; 7. grobbent, 211, 249 fF, 250 Trypanoplasma, 168, 209, 211, 217, 249; 7. borrelt, Pili. cat. 2Lo/.,. 216, 217, 249; 7. cyprini, A fe al, 249: 7, intestinalis, 247, 249, 250 7.3; QT. ventricult, INDEX 247, 249; 7, 249 varium, 157, 168, 168, 177, 248, 250; 7. avium, 208 f., 217, 2538 ; T. barbatulae, 215, 227, 228, 230 ; 7’. boneti, 254 ; T. bruci, 195, 199 fr, 200, 201, 203, 208 f, 909, 214, 215, 216, 217, AR0 ji, eal f., 220. f. 231, 233; TZ. carassii, 200 <2. eo0ttie, 25D": T. costatum, 254; T. damoniae, 208 f., 254; T. danilewskyt, 204 ; T. dimorphon, 253; 7. duttoni, 205; T. elegans, 255 ; T. elmassiani, 253 ; T. equinum, 197, 199 f., 205, 208.7., 217, 220-7, A221 7.5 224 f., 251. f,, 253; T. equiperdum, 197 m., 205-7, 209; BLA fxg LOL Jog aoe 5. 2: evanst, 199 7, 253°; 7. flesi, 255 ; T. gambiense, 196, 197 x., 199, 200, 203,208 7.5, 220-f., 221 Su 20s. DO f.9 20a Fk. granulosum, 204, 209, BOOT, 2aey AOS! 2, grayt, 200 n., 201, 215, 2167., 2247, 23), 2327., 233, 245, 246, 251; 7. hannae, 208 f., 209, 216, 253, 254; T. inopina- tum, 210 f., 216, 255; T. johnstonit, 214 xn, 253 f., 254; TT. karyo- zeukton, 210 7, 212, 255; T. lewisi, 197, 198, 208, 204, 205, 207 fF, BUS 7... 220, 201 70, 214, BiG, 2h 200 fF, 5.222. 220 fF. A260: f., 229; 251 n., 252; T. mega, 212, 255; T. nanum, 209; T. nelsprwitense, 210 f,, 255; 7. noctuae, 198, 202, 205, 208 /., ald) ZLB, 219 7. 228, 233, 242, 243, 247, 248 ; Ee paddae, 2533 T. polyflectri, 209 ; T. raiae, 204, 209, 216, 224, 228, 231, 255 f.; ZT. remaki, 204; 209, 210 7, 216; T. rotatorium, 208, 209, ZA Jos DIG. 248: wm, 250n., 254; 7. sanguinis 295 avium, 195 f., 254; 7. scyllii, 204, 255 f.; 7. soleae, 210 f., 217; T. theileri, 199 f., 209, 251 n., 253; ZT. trans- vaaliense, 216, 253; T. ugandense, 252; T. un- dulans, 255 ; 7. varium, 227; 7. ziemanni, 205, 208 f., 233, 237 f., 238, 253 Trypanosomatidae, 248 Trypanosomes, 193, 213 f. Trypanozoon, 248 Tsetse-fly, 196, 201 7. Tubulina, 63 ; 7. stipitata, 56 Tubulinaceae, 63 Tulloch, 199, 200, 208, 230 Tuscarora nationalis, 122 be Ne a Tuscaroridae, 150 Tuscarusa globosa, 150 f. Ulothrizx, 156 Ulotrichaceae, 156 Umbilicosphaera, 176 Undulina, 250 Urceolus, 171 Urogiena, 158,173, 176 ; U. ranarum, 166 f., 194 J, 195, 254; U. volvox, 1667. Urophagus, 169 Vacuolaria, 174 Vahlkampf, 70, 92 Valentin, 194 Vampyrella, 2, 3, 4f,, 5, T f.5°19,.58 Vampyrellidium, 2, 3, 8 Veley, 71, 81, 92 Vernon, 98, 152 Verworn, 18, 95, 152 Voges, 272 Volvocina, 181 Volvos, - 158, 281 *- aureus, 182 ; V. globator, 166 f., 181; V. minor, 166 /. + V.tertvus, 182 Wagnerella, 34 Wasielewsky, 212, 272 Watase, 189 Wenyon, 192 © West, .G.-°S., 192 13,.~ 36: 296 4 INDEX Wolfenden, 113, 152 Xiphicantha slate 128, egictihation -" Radio- — \ra Woodcock, 193 n., 268 142 f., 148 - aria, 97 Woronin, 3, 13, ‘3S, 66, | Zopf, 2, 5,-6 n., 18, 39, 3 173, 192 Zederbauer, 192 60, 61, 67, 280, a Wright, S., 13, 256, 273 | Zoochlorella actinosphaerii,| 283 ‘ ee 2 - 22 Zuelzer, 71, 86, 87,92 Xanthellae, 22 Zoospores, in Mycetozoa, Zygacantha, 146; Z. =e Xenophyophoridae, 284, 40; in Proteomyxa, 4 tentrionalis, 146 ; 286 Zooteirea, 33 Zygoselmis, 171 — 7. = j Printed by R. & R. 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