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Sage ceive 1891 A-2oi wil golalaoe roy 5901 DEPARTMENT or ZOOLOGY Cornell University Lib QL 367.4. C33 relty Ubrary The British fresh Hel roti teciens rota THE RAY SOCIETY. INSTITUTED MDCCCXLIV. This volume is issued to the Subscribers to the Ray Socrrry for the Year 1905. LONDON MDCCCCV. THE BRITISH FRESHWATER’ RHIZOPODA AND HELIOZOA BY JAMES CASH ASSISTED BY JOHN HOPKINSON, F.LS., F.R.MS., Erc. ‘ Secretary of the Ray Society VOLUME I RHIZOPODA, PART I LONDON PRINTED FOR THE RAY SOCIETY 1905 ' PRINTED BY ADLARD AND SON, LONDON AND DORKING. PREFACE. THE main object in the preparation of this work was to bring together, as concisely and accurately as possible, in a single manual, all that has been so far discovered regarding the British Freshwater Rhizopoda and their near allies the Heliozoa. The labours of Dr. Penard of Geneva have resulted in his giving to the world exceedingly valuable mono- graphs of the Rhizopoda and Heliozoa of Central Europe, and of Switzerland in particular; and it is to be regretted that no British Biologist of equal standing has done the same for this country, which is certainly not less rich in species. The present attempt at a classified description of these microscopic animals will it is hoped lead to other workers entering upon a field of research which is fascinating in a high degree even to the general microscopist. The biological student will find in this manual an honest effort, at least, to describe the species which have hitherto been met with in this country, to give their usual habitats, and to point out the characters by which they may be most easily identified. I do not profess to have investigated very close- ly the physiological problems associated with the life-histories of these organisms; the minute and continuous observations which are necessary for that v1 PREFACE. can scarcely be undertaken by one possessing only occasional opportunities for their study; but this monograph it is hoped will help to show that a large amount of inviting material lies ready to the hand of the earnest student. The field is a wide one. Besides the structural beauty of the Rhizopoda and the interesting phases of their life-histories, the possibilities open to anyone of discovering new and previously unsuspect- ed forms in our ponds and marshes, are practically unlimited. Whilst holding myself responsible for all imicro- scopic and descriptive work in the preparation of this monograph, I desire to express my indebtedness to Mr. John Hopkinson for the assistance which he has rendered to me, particularly in working out the synonymy of the genera and species described. This has entailed upon him an expenditure of time and labour which cannot be too generously acknowledged. Mr. Hopkinson has in preparation a Bibliography of the Freshwater Rhizopoda and Heliozoa which will appear in a future volume of this work. To him I am also indebted for the suggestion of the term Conchulina as applicable to the shelled freshwater Rhizopoda. The discarded “ Testacea ’’— a term pre-occupied in the Mollusca—is unsuitable, and its continued use is undesirable. Conchulina, besides being strictly accurate, is also especially appropriate to these minute organisms. JAMES CASH. SALE, MANCHESTER, 27th October, 1905. CONTENTS OF VOL. I. z PAGE IntRODUCTION . : ; 1 CLASSIFICATION ‘ ; ; . 84 Cuass SaRcopina. Svs-cLass RH1zopopa . 39 OrnDER I. Ama@pina : i : 39 Famity 1. Loposa : s 39 Genus 1. Ama@pa . ; : . 40 2. DACTYLOSPHERIUM . 64 3. Masticama@Ba 5 ; 69 4. PrLomyxa : ; ‘ : . 73 5. LirHam@Ba : 2 . 8 6. OURAM@BA d . : . 83 Famity 2. Rericunosa : 4 . 85 Genus 7. GyYMNOPHRYS : ; . 86 8. Bromyxa : ‘ 88 9. PENARDIA , . 89 10. Catamypomyxa : 91, 140 Famity 3. VAMPYRELLIDA . : . 94 Genus 11. VampyRELLa 95 12. Hyaxopiscvus . . . . 106 18. NucLEARIA : . 109 14. ARCHERINA . 112 OrpeR II. ConcHULINA . . 115 Famity 1. ARCELLIDA. : . 11d Genus 15. ARCELLA Z 117, 138 16. PsEUDOCHLAMYS 3 ‘ . 129 17. CENTROPYXIs . : .. 131 INDEX OF SPECIES, ETC., DESCRIBED 5 . 146 LIST OF THE PLATES. PLATE I—Figs. 1-6—Ameba proteus. Figs. 7-10.—A. actino- phora. Il.—Ameba villosa. IIl.—Fig. 1.—Ameba limax. Fig. 2.—A. proteus. Figs. 3-5,.—A. gorgonia. Figs. 6, 7.—A. striata. Figs. 8-11.—Dactylospherium radiosum. Fig. 12.—D. polypodium. IV.—Figs. 1-5.—Ameba pilosa. Figs. 6-11.—Dactylo- spherium radiosum. Fig. 12.—D. polypodium. V.—Figs. 1-3.—Ameba verrucosa. Fig. 4.—dA. guttuta. Fig. 5.—Lithameba discus. Fig. 6.—Ourameba voran. VI.—Figs. 1-5.—Mastigameba aspera. Fig. 6.—M. ramu- losa. VII.—Figs. 1-3.—Pelomyxa palustris. Figs. 4-6.—P. villosa. VIII. —Figs. 1, 2.—Gymnophrys cometa. Figs. 3, 4.—Biomyaa vagans. IX.—Penardia mutabilis. X.—Vampyrella lateritia. XI.—Figs. 1-3.— Vampyrella lateritia. Figs. 4-6.—V. voraw. Figs. 7-12.—V. flabellata. Figs. 13-15.—V. gomphonematis. XII.—Nuclearia delicatula. XTI.—Fig. 1.—Nuclearia conspicua, Figs.2-11.—Hyalodiscus rubicundus. XIV.—Fig. 1.—Chlamydomyxa labyrinthuloides. Figs. 2-6. Archerina Boltont. XV.—Figs. 1-8, 11-17.—Arcella vulgaris. Figs, 4-6.—A. discoides. Figs. 7, 8.—A. dentata. Figs. 9, 10.— A. mitrata. XVI.—Figs, 1-9.—Pseudochlamys patella. Figs. 10-16.— Centropywxis aculeata. ILLUSTRATIONS. IN THE TEXT. FIGS. PAGE 1.—Pelomyxa palustris : portion of periphery ‘ 6 2.—Amcba proteus: pseudopodia . . . 10 3.—Inthameeba discus ; pseudopodium ‘ . 10 4,—Biomyxa vagans : pseudopodia . i 11 5.—Ameba proteus: diagram of pseudopodium . 12 6-9.— 53 contraction of vacuole . 18 7.—Hyalosphenia papilio : test 3 : 17 8.— Difflugia pyriformis : test. : s . 17 9.—Sphenoderia fissirostris : test : . 18 10.—Quadrula symmetrica : test ‘ ‘ . 18 11.—Trinema enchelis: test . : . 18 12.—Microgromia socialis ; reproduction . 24 13.— Diflugia pyrifornis : conjugation ‘ . 25 14.—Nebela collaris: conjugation. : . 25 15.—Ameba proteus: dissolution. . . 29 16.—A. limicola ‘ : > . 56 17, 18.—Arcella vulgaris: test. , f . 120 10 8 var. gibbosa . 5 . 120 20.—A. discordes : ; ; . 128 21-23.—A. dentata ; ’ ; ‘ . 127 24, 25.—A. artocrea : 5 ; 5 . 128 26.—Centropyxis aculeata var. spinosa : . 1385 27.—C. levigata : : ; : . 137 28.— Arcella vulgaris var. compressa . ; . 139 29.—Chlamydomyxa montana: active state . . 141 30.—C. montana: pseudopodal filaments. . 148 31.— ,, 3 fragment of body. : . 148 32.— ,, 9 encisted state : . 145 All measurements, except when quoted from other authori- ties, are expressed in micromillimetres (2). 1 = 0-001 mm. or 0:00003937 (ss45,) of an inch. BRITISH FRESHWATER RHIZOPODA. INTRODUCTION. Tue Rhizopoda are animals of minute size and rudimentary structure, forming, with the Heliozoa and Radiolaria, the class Sarcodina of Biitschli. The term Rhizopoda—literally meaning “ root-footed ”— now almost universally adopted, was invented by the French naturalist Dujardin to distinguish ‘“ animals provided with variable processes.” The Sarcodina, with the Mastigophora (flagellate animals), the Sporozoa (a group of endo-parasites), and the Infusoria, make up the sub-kingdom of the Protozoa, which is represented by some 1600 genera and many thousands of species. For present purposes we are not concerned with the Mastigophora as a group (though, as will be seen later, they bear some relationship with the lobose Rhizo- pods), nor yet with the Infusoria or the Sporozoa. The Radiolaria, also, are excluded from consideration by the fact that they are marine; they possess ray-like pseudopodia resembling those of the Heliozoa, but differ from animals of that sub-class in having a compara- tively large “central capsule,’ which is membranous, minutely perforated, and marked, usually, by lines which divide its surface into polygonal segments. The whole of the Protozoa are microscopic crea- tures. Their existence was not even suspected until 1 2 BRITISH FRESHWATER RHIZOPODA. Leeuwenhoek (cies 1675), with his simple lenses, began to examine drops of pond-water, and discovered some of the commoner ciliated forms. Continued observation by this naturalist and his contemporaries revealed a variety of life-forms; and for many years their origin, organization, and functions were matters of lively controversy. The theory, at first prevalent, of spontaneous generation, was in process of time abandoned ; but even so late as the time of Ehrenberg, one of the most assiduous, though not always most accurate, of observers, their unicellular structure, now universally conceded, was doubted. Imagination con- ceived what the imperfect microscopical appliances of the time failed to reveal, and the impression was formed that they were possessed of organs analogous to those of the Metazoa. Ehrenberg (1838) pictured them with many stomachs, and from that fancied character applied to them the title, now obsolete, of Polygastrica. The greater perfection and higher powers of modern microscopes have contributed to the elucidation of the structure of the Protozoa and of their life-functions. Structurally they are simple cells, or single corpuscles, of protoplasm. Siebold, Kélliker, and Max Schultze early demonstrated the groundlessness of Ehrenberg’s theory. Dujardin, together with Biitschli, Auerbach, Claparéde and Lachmann, Hertwig and Lesser, as well as our own countrymen Dr. Wallich, Mr. H. J. Carter, and Mr. William Archer, extended our knowledge of the tribe materially. More recently the physiological relations and classification of the Rhizopoda have been studied, and the results recorded, by Professor Ray Lankester and others, in the pages of the ‘ Encyclo- pedia Britannica,’ the ‘Journal of the Linnean Society,’ the ‘Quarterly Journal of Microscopical Science,’ and elsewhere. Naturalists abroad have for years worked unceasingly in the same field, and the scientific publications of Germany, Switzerland, Italy, and France, for more than a generation, have afforded evidence of the keen observation of Greeff, Gruber, INTRODUCTION. 3 Cienkowsky, Verworn, Rhumbler, Blochmann, Penard, Maggi, Cattaneo, and Dangeard; whilst Professor Leidy, by the publication in 1879 of his classic ‘ Fresh- water Rhizopods of North America,’ stimulated observa- tion in this department of zoology in his own country. PROTOPLASM AND CELL-STRUCTURE. The constituent element in the composition of the Rhizopoda is protoplasm, the living matter, as physio- logy teaches, “from which all animated beings are formed and developed, and to the properties of which all their functions refer.” They present no differentia- tion of tissues or of organs; their bodies are contractile, and for the most part translucent, resembling, as has been aptly said, a tenacious mucus, or soft tremulous jelly ; whilst their movements, always slow and erratic, seem aimless, except for the supply of the primary need of an animated being—the acquisition of food. The Rhizopoda, in common with all primitive life- forms, are unicellular. It is desirable, in order to make clear the significance of this term, to say a few words regarding the structure, etc., of the simple cell. The cell, physiologically, is a minute vesicle, or closed sac, the enveloping membrane or cell-wall enclosing the protoplasmic substance in which the functional phenomena reside. Of such cells—modified, of course, and more or less differentiated—the bodies of all animals are built up. A recent American writer * thus summarises the ascertained facts in this connection. The protoplasm of an ordinary typical cell in the Metazoa, as well as in the higher plants, is differentiated into cell-body or cytoplasm, and nucleus, of which the difference in chemical composition is considerable. The former is rich in proteids (albumen playing the most important part) and poor in phosphorus. The nucleus, on the other hand, is rich in phosphorus bound up in a substance called nuclein, but poor in albumen. * Dr. G. N. Calkins, ‘ The Protozoa’ (1901), chap. viii. 4 BRITISH FRESHWATER RHIZOPODA. Tut Proropuasmic Bopy. The fact that no distinct membranous envelope can be detected in the naked protoplasts (e.g. Amaba proteus) does not nullify the assumption of their unicellular nature. Auerbach asserted that such an envelope does, in fact, exist ;* but his view has been rejected by later observers. It was strenuously opposed by our countryman Dr. Wallich, whose conclusions, published in 1863, remain unrefuted.t Wallich showed that ectoplasm and endoplasm (terms denoting the outer layer and the more fluid inner substance of the plasma- body) are not “permanent portions of the protean structure, but mutually convertible one into the other, and that it is an essential feature of sarcode that while the outer layer is, for the time being, ipso facto instantly differentiated into ectosarc, the same layer reverts to the condition of endosare.”’t That portion of the plasma-body (referring more particularly to the Amebx) which is in immediate contact with the sur- rounding medium acquires a certain density, by co- agulation or some process analogous thereto, whilst the central mass, containing granular matter, incepted food, etc., remains semi-fluid. The same view has more recently been expressed by Prof. Ray Lankester. He maintains that ectoplasm and endoplasm “are not to be understood as distinct layers, but are one and the same continuous substance ; what is external at one moment, becoming internal at another ; no real structural difference existing between them.” Gruber, as the result of independent observations, and without reference to Wallich’s view, arrived at the same conclusion.§ He was definitely and decidedly of * «Zeitschr. fiir Wiss. Zool.,’ vii (1856), + ‘Ann. and Mag. Nat. Hist.’ (3) xi (1863), pp. 369, 370. t The terms “ ectosare ” and “ endosare” are synonymons with ectoplasm and endoplasm. The latter are now in more vencral use. § ‘ Biologischer Centralblatt,’ vi (1886). INTRODUCTION. 5 opinion “that no division of the Rhizopod body into zones, sharply differentiated morphologically and physiologically, occurs, and that the interpretations which have been made in this sense are decidedly founded upon illusions.” His remarks had reference more especially to the publications of two authors, one of whom, Maggi,* had asserted the existence, not only of an endoplasm and an ectoplasm, but also of a ‘“ meto- plasm,” in which he supposed were seated the secretory organs of the Rhizopod, namely, the contractile vacuoles, whilst the ectoplasm served for locomotion and the endoplasm for digestion. The other, Brass, went somewhat further. He professed to distinguish within the Rhizopod body, and, indeed, in the Infusoria generally, as well as in the animal cell, four kinds of plasma, namely (proceeding from within outwards) the nutritive plasma, the food-plasma, the respiratory plasma, and the motor-plasma. These views had already been refuted by Biitschlit so far as they related to the Infusoria, and Gruber considered that Biitschli’s objections applied equally to Brass’s work, so far as it bore on the Rhizopoda. ‘ Whoever,” he remarked, “has long busied himself with the study of the Rhizopoda, knows how many species there are, especially among the dinwbe, in which, during life, no division into separate zones occurs; in which the whole of the contents of the bodies; as well as the nucleus and vacuoles, are irregularly whirled about, so that, for example, the nucleus (or the nuclei) may be at one time pushed to the extreme periphery, and then again flow back into the centre of the body. If in such Rhizopoda, after the application of reagents, an ap- parent separation into different. plasma-layers occurs, these may be definitely regarded as artificially produced, in face of the conviction arrived at during the hfe of the animal.” Gruber supports his view by areference to Pelomyaa * «Atti Soc. Ital. Sci. Nat.,’ xix, fasc. 4 (1876). +t ‘Morphol. Jahrb.,’ xi (1886). 6 BRITISH FRESHWATER RHIZOPODA. and certain of the Amwbe, in which often no ectoplasm can be distinguished. Under certain circumstances even here, “ such a hyaline external plasma-layer makes its appearance, and this consequently must have.been produced from the granular plasma in the way in which, locally bounded, a hyaline pseudopodium is evolved from the body of a Rhizopod consisting of granular plasma.” Concerning the external limita- tions of the Rhizopod body, he says that it is naked, ‘but it would appear that by contact with water,” as Dr. Wallich had previously shown, “a stiffening of the plasma takes place at the periphery, preventing its Fig. 1— Portion of the periphery of Pelomyaa palustris when at rest, with the endoplasm (en) and ectoplasm (ec) sharply defined as frequently seen, and an outer fringe of minute projections from the latter. x about 150. deliquescence, and also causing an immediate closure of the cut surface, in case of artificial division. When the protoplasm ‘issues forth in a broad process, in the form of pseudopodia, the former bounded portion dis- solves in the advancing plasma, to become re-formed at the same moment.” This author acknowledges the prior claim of Dr. Wallich to the discovery. Dr. Wallich was also the first to explain the production of the nutritive vacuoles, by assuming that a drop of water is carried in along with the -incepted food-particles, and that this exerts the known stiffening action upon the portions of plasma surrounding the bodies incepted, “so that every nutritive vacuole appears to he lined with an ectosarcal layer.” INTRODUCTION. 0 The conclusions of the authors cited represent, broadly speaking, the present state of our knowledge upon this subject. It may be said to accord with general observation that, so far as there is a regional difference in the plasma-body between endoplasm and ectoplasm, it possesses no morphological significance, but is, as Calkins observes, “ only an index of the physical conditions of the protoplasm.”* Tue Nucteus. The nucleus plays an important part in the develop- ment and functions of the protoplasmic cell. There are certain organisms belonging to the Monera of Heckel (e.g. Biomyxa vagans) in which no nucleus has yet been satisfactorily demonstrated. It does not follow, however, that nuclear substance is absent, for, as Calkins says, nuclei are “almost as varied in the different forms of Sarcodina as are the different types of the animals as a whole.”t+ In some cases where a nucleus is present, it is ill-defined, the chromatin, a part of the nuclear substance stainable with certain basic dyes, being scattered in the form of granules throughout the entire cell. It is possible, this author further says, to conceive of non-nucleated organisms, although the numerous experiments on nucleated and non-nucleated parts of Protozoa show, in these cases at least, the absolute necessity of the nucleus for the life of the individual. The nuclei observed in different species of Rhizopoda vary in point of number. This is not always uniform in members of the same genus. Usually asingle nucleus is present, varying in size and well defined; in certain of the Lobosa and in some Heliozoa there are two or more; in Pelomyxa palustris, nuclear bodies, it is asserted, can be counted by the thousand. The testaceous genera (Arcella, etc.) are in many cases multinucleated. There may, in some forms, be a mem- * ©The Protozoa,’ p. 38. + Op. cit., p. 86. 8 BRITISH FRESHWATER RHIZOPODA. brane and a single compact mass of chromatin, which occupies the centre of the distinct nucleus and is separ- ” ated from the membrane by hyaline matter. In others the chromatin reservoirs may be two or more, or there may bea great number of granules in the nucleus with- out the reservoirs (e.g. dineba proteus). ‘ In some of the Rhizopoda (Luglypha) and Heliozoa (Actinophrys and Actinospherium), the nucleus is strikingly similar to that of metazoan cells, consisting of chromatin in the form of a reticulum, and a network of linin.” * A true nucleus, comparable to the nuclear structure in Metazoa, according to Hertwig, apparently exists in no case, save possibly in Actinospheriwm, and even here it is limited to a passing phase during cell-division. Discussing this subject Calkins remarks on the prob- ability that the structures which have been almost universally, but erroneously, called nucleoh, do not belong at all to this category of nuclear elements, but represent either the functional chromatin which is aggregated into a central mass (karyosome) during the quiescent or vegetative period of cell-life, or the intra- nuclear division-centre. This author thus summarises the observations of Gruber, Hertwig, Brauer, and others upon the pheno- mena presented by the nucleus, during mitosis (cell- division), and concludes: “The facts point toward the conclusion that the centre of activity in the division of the protozoan cell, as in Metazoa, resides in a special structure, which, to avoid confusion in terminology, has been called the division-centre. In some cases this structure resembles the astral system of Metozoa, in’ consisting of an outer spherical mass with radiating processes (astrosphere), and an inner focal granule or granules (centrosome). The evidence further tends to show that the division-centre in Protozoa consists of a specific substance different from the chromatin and from the cytoplasm, and possessing above all other portions of the cell an active ;d/+ in division. No con- ™ Calkins, op. cit., p. 87. INTRODUCTION. 9 clusive evidence is forthcoming to show whether this substance is permanent in all cells, and whether it was originally nuclear or cytoplasmic in origin, although the widespread intra-nuclear condition favours the view that it originated there.’’* The importance of the nucleus in the economy of all unicellular organisms has been well established. With- out it the function of digestion cannot take place. Hofer in 1889, and Verworn later, demonstrated that no digestive fluid is prepared in the cytoplasm when the nucleus is absent. Hofer also held that the slimy * secretion by which the common Ameba anchors itself before food-taking is never formed by the enucleated portions ; and Verworn in 1888 showed that enucleated pieces of Polystomella (one of the marine Foraminifera) could not repair or regenerate the lost shell, while nucleated pieces quickly repaired it. The conclusion of this observer was that enucleated protoplasmic masses cease entirely those chemical processes by which pro- ducts of the normal shell are used or formed. The generalisation may now, Calkins concludes, be made that no secretion takes place in enucleated fragments. On the other hand, the nucleus, by itself. e. separated from the cytoplasm—has no longer the power to regenerate the lost parts, and like the enucleated cyto- plasm, soon dies. Biitschli’s conclusion that “ the nucleus needs the plasm, the plasm the nucleus,” seems well grounded. Their activities are reciprocal. One without the other cannot live. The process of secre- tion, therefore, whether for the purpose of digestion, or whatever else, in the life of the unicellular organism, is expressed by constant chemical interchange between the cytoplasm and the nucleus. Means or Locomorion. Except in a small number of species, the Rhizopoda are endowed with the power of locomotion through * Op. cit., p. 278. 10 BRITISH FRESHWATER RHIZOPODA. the agency of pseudopodia. In the Amcebina, Arcellida, and other lobose forms, these ‘‘ changeable processes ” are usually few in number, short, digitate, and blunt at the tip; or they may be broad and lobose—in the Amabe they are most frequently so—whilst in the Euglyphe and others, included in what Leidy classed as the Filosa, they are acicular, sometimes short, but more frequently of considerable length, and capable of branching, and also, in a small number of forms, of anastomosing. These acicular pseudopodia may be rigid and susceptible of little apparent change for longer or shorter periods ; often, however, they change rapidly, or they may whilst fully extended (e. g. Fies. 2 and 3.—Examples of pseudopodia. 2.—Digitate and branching pseudopodia of Ameba proteus, showing also nucleus, (n.) and contractile vacuole (c.v.). x about 150. 3.—Eruptive (hernia-like) pseudopodium of Lithameba discus. Cyphoderia) sway to and fro, bend at an acute angle, or become curved, or take other forms. In some of the Reticularia (Proteomyxa, Ray Lankester) they branch out remarkably, and form a widely-spread net- work, which, like a spider’s web, serves to capture prey. This is conspicuously the case in Penardia. The Heliozoa in some cases (probably in most) have radial filaments, the centre of which is occupied throughout its entire length with a thread of “ stiffened protoplasm.” In the mele changes of form are sometimes very rapid. The production of pseudopodia, or rather the contributing cause, has been a subject of lively con- troversy. ‘The theories of the early observers were as INTRODUCTION. 11 fantastic as they were varied. “Contractile fibres”’ served for a time to explain the phenomena of motion. Gruber advanced the theory of “ pressure from behind.” There was, he held, a push forward of the more fluid contents by the posterior ectoplasm, after the extrac- tion of water had given the latter a tougher consis- tency. The posterior extremity was “drawn into threads as the Ameba advances, and the effect of a reversal of the direction of movement, he said, was seen ma flow of ectoplasm from the posterior region, the more tenacious protoplasm appearing then on the oppo- site side.* Dr. Wallich disputed Gruber’s theory, and reiterated a view which he had long previously expressed, namely, Fic. 4.—Anastomosing pseudopodia of Biomyza vagans. x about 150. that the rush of granules is not dependent upon any previous contractile effort exercised in the posterior region. The flow merely takes the place of the ectosarc which has been suddenly projected forward. Hence, he argued, the motion is dependent on the contractile power of “the external sarcode layer, and the endosarc only passively participates in it.” + Calkins sums up the controversy by remarking that of late years, especially since Bitschh’s masterly work on the structure of protoplasm, there has been a general tendency to abandon the older theory of contractility, and to explain the movements of ameceboid bodies through the physical laws of liquids, and in particular the laws of surface-tension. The origin of a pseudo- * «Zeitschr. fur Wiss. Zool.,’ xl (1884). + ‘Ann. and Mag. Nat. Hist.’ (5) xvi (1885), p. 215. 12 BRITISH FRESHWATER RHIZOPODA. podium is clearly in the ectoplasm, and the rapidity of its formation is increased by the peculiar ‘“ fountain currents” characteristic of most pseudopodia. As observed by Bittschli, an advancing stream of granules flows through the centre, or axis, of the growing pseu- dopodium, while near its apex return currents, “like the falling drops of water in a fountain,” surround the central stream.* Rhumbler (1898) adduces the harden- ing effect of water on protoplasm (first suggested by Dr. Wallich) as explaining the formation of new ecto- plasm, and the increase in surface of an advancing pseudopodium. The outer ectoplasm has a firm con- sistence, and as Rhumbler demonstrated by treatment Fig. 5,— Diagrammatic representation of apseudopodium of Ameba proteus. The central arrows represent the forward flow of the endoplasm, the marginal ones the (apparent) “return currents.” with diluted caustic potash—in the case of Amba verrucusa—may be isolated from the endoplasm. Nevertheless, it is converted into streaming endoplasm again. The conversion of ectoplasm into endoplasm, and vice versd, in the activities of the Amabu, is a constantly-recurring phenomenon. But explanations of this nature, as Calkins Says, based upon purely physical laws of fluid substances, seem inadequate to explain all types of pseudopodia, the reticulate and long filamentous forms in particular. “Up to the present time,” this author remarks, “no satisfactory and comprehensive explanation has been made, and it should he recognized that the theories advanced still remain only working hypotheses.” * The “return currents ” are more apparent than real. INTRODUCTION. 13 Tue ConrractiLy VACUOLE. The freshwater Rhizopoda, with but few exceptions, exhibit in some part of the plasma at least one con- . tractile vesicle, of which the functions are as yet but imperfectly understood. In the Amabe it follows the streaming of the endoplasm. In the testaceous forms (e. g. Arcella, Huglypha) the number of vacuoles varies ; they occupy a more definite place in the protoplasm, and are, as a rule, of smaller size. The action of the vesicle is best seen in the familiar sun-animalcule, Actinophirys sol, one of the Heliozoa. e periphery of the body, bulg- Fic. 6.—Four stages in the contraction of the vacuole in Ameba proteus. xabout 400. (After Calkins.) ing outwards conspicuously during diastole, and, if note be taken of the intervals of discharge, the time will be found to approach sixty seconds. The fre- quency of the pulsations, however, is not the same in all species. The period between diastole and systole is longest in the testaceous forms. There is considered to be an indefinable relation— actual connection has not been proved—between the contractile vesicle and the nucleus. It is found that, as the vesicle gets filled it falls towards the posterior region by reason of its greater weight as compared with the enclosing endoplasm, and that finally reaching the ectoplasm its contents are discharged outwards. This, however, is not easily demonstrated. Calkins traced the formation and contraction of the vacuole 14 BRITISH FRESHWATER RHIZOPODA. and the expulsion of the contents, step by step, under a high power. Its reappearance he found to be always somewhere near its point of disappearance. ‘ While still small it is carried along by the streaming proto- plasm back to a position near the nucleus, where it completes its development. The increasing weight of the growing vacuole causes it to lag behind the stream- ing granules and nucleus, until at its full growth it is widely separated from the latter organ. The vacuole may appear to move in the direction contrary to that of the protoplasmic streaming, although in reality it is quiescent; for while it remains in the field of the microscope the main body of the animal moves well out of it, until the vacuole is surrounded only by the posterior end of the animal, which is reduced to a thin layer of granules and a hyaline layer of ectoplasm between the vacuole and the exterior. The granules later move away, passing around the vacuole, until finally there is only a thin layer of hyaline plasm between the vesicle and the exterior. Shortly after this the vacuole bursts and disappears, in most cases a distinct bulge toward the outside preceding contraction. Contrac- tion always begins on one side of the vacuole, and is carried across it toward the outer edge.”’* The action of the contractile vesicle, doubtless, has an important physiological meaning. The generally- accepted view is that the periodical discharge is an excretory function. The excess of water in the plasma- body drains mto the vacuole, and is thus got rid of. In the more highly-organised Infusoria the water is conveyed to the excretory vacuole by a system of ducts. Such channels have not been seen in the endoplasm of the Rhizopoda; but whatever the means employed by Nature in their case may be, the effect is the same. Inception or Foon. The food of the Rhizopoda is, in the main, chloro- phyllous. It consists of diatoms, desmids, and spores * Calkins, op. cit., p. 88. INTRODUCTION. 15 of Algee. Some species, however, prey upon Rotatoria and other microscopic animals. They seem to have a certain selective power; but thisis not universal. It is supposed to be absent from Amaba and Pelomywa, which surround with their pseudopodia, and draw in, whatever comes in their way. In certain of the Vampyrelle a power of selection is very pronounced. The Reticularia, according to Verworn, normally take in only living organisms. Some of the Heliozoa—e. 9. Actinosphertwm—capture both infusorians and rotifers, but their staple food, like that of the Rhizopoda in general, is chlorophyll, derived from the sources already mentioned. In Ameba proteus, which may be taken as typical of the order Amcebina, food, of whatever kind, may he incepted at any convenient part of the body-surface. A pseudopodium is directed towards the object encoun- tered—say a diatom—and flowimg around it forms a “ oastric vacuole.” In this the diatom remains until digestion is completed. Finally, the siliceous frustule, deprived of its chlorophyll, is ejected. The chloro- phyll, from whatever source derived, is seen rolled into balls or pellets and scattered through the endoplasm, giving to it a more or less green tinge. The water, entering the gastric vacuole along with the food, is believed to change gradually by osmosis with the fluids of the plasm. These contain a digestive acid which reduces the digestible portions of the food probably to some form of peptone, and this, again by osmosis, is then assimilated in all parts of the endoplasm. A remarkable similarity has been found to exist between the action of the naked Lobosa and certain fluid substances, and upon this some ingenious theories have been constructed. Rhumbler, in 1898, following suggestions and experiments made previously by Hofer and others, demonstrated that a drop of chloroform will attract a shellac thread from the surrounding water and roll it up within its substance, just as an 16 BRITISH FRESHWATER RHIZOPODA. Ameba rolls up a filament of conferva.* HEgg-albumen and gum-arabic in solution evinced the same pheno- mena, the rapidity of ingestion showing the density of the medium. These phenomena accord with physical laws. Rhumbler found that a splinter of glass inserted” in a drop of chloroform suspended in water will leave the chloroform and seek the water, but that, coated with shellac, and then placed in contact with the chloroform drop, the splinter and shellac were quickly drawn into the chloroform. So soon as the shellac was dissolved by this medium, it was expelled, or, to put it more cor- rectly, drawn into the surrounding water, by reason of the greater co-efficient of adhesion between glass and water. Rhumbler drew an analogy between this and the process of feeding in the Rhizopoda. Bodies, he concluded, are ingested into the plasma because of the greater attraction to the fluid protoplasm than to the water; then, through the chemical changes between protoplasm and the digestible parts of the foreign sub- stances, the constituents of. the body are changed, and a corresponding change is wrought in the attractive force which keeps them together, that is, in the co- efficient of adhesion, and defecation results. Tue Tests. The tests of the freshwater Rhizopoda are variable in size and form, as well as in the materials of which they are composed. The simple membranous test of the Cochliopodia, or that of Pamphagus hyalinus, may be regarded as the most rudimentary. It is formed by the secretion of a chitinoid substance, apparently during the life of the imdividual. From this, as a starting point, we get a great diversity of structural types, from the homogeneous tests of the Hyalosphenix to the tesselated ones of Nebela and Euglypha, and the coarser Difiiigie, which, not content with a purely « An Amaba 90 p in length absorbed and coiled up an Oscillaria filament measuring 540 p. INTRODUCTION. 17 chitinous envelope, fortify and ornament it externally with sand-grains, diatom-tests, and other extraneous substances. The tests of Hyalosphenia are either plane-surfaced, or ornamented with variously-disposed pits or depres- sions. Those of Nebela and Huglypha are built up of circular, oval, or hexagonal plates, placed edge to edge, or with the edges overlapping. The development of the Rhizopodous tests has been closely studied by Gruber, Verworn, and others. In Fic. 7.—Test of Hyalosphenia papilio. x about 250. Fie.8.—Test of Diflugia pyriformis (a common form) encrusted with sand- grains. x 200. Buglypha alveolata Gruber concluded that there was a development, within the protoplasmic body, of the necessary materials—chitin, cellulose, or silica—by chemical agency. Diaphanous plates of varied pattern, circular or oval (Nebela, etc.), polygonal (some Euglyphz); quadrangular (Quadrula); or of no definite geometrical figure, are secreted; and during mitosis (reproductive fission) these so arrange themselves in the newly-formed cell as ultimately to form an external covering, in all respects like that of the parent.* It is * © Zeitschr. fir Wiss. Zool.,” xxxv (1881), 431. See also Schewiakoff in ‘Morphol. Jahrb.,’ xiii (1888). 9 18 BRITISH FRESHWATER RHIZOPODA. suggested that in the case of Huylypha the secretions take place in the ectoplasm. In some Rhizopoda (e.g. Sphenoderia) the test is apparently siliceous. Silica also enters into the com- position of the test of Nebela dentistoma, as appears by its breaking, under pressure, with an irregular frac- ture. Simple chitinous membrane, as seen in most Nebelx, etc., does not fracture when subjected to pres- sure. The homogeneous plane tests of Arcella, Cyphoderia, and some others, are finely punctated. Pseudochlamys secretes a simple protective shield, which, in the earlier stage of the animal’s existence, is Fic. 9.—Transparent test of Sphenoderia fissirostris, composed of large oval plates. x 375. Fie. 10—Transparent test of Quadrula symmetrica, composed of quadrangular plates. x 375. Fig. 11.—Ordinary form of test of Trinema enchelis. x 375. flexible and susceptible of constant change in sympathy with the creature’s movements. It is not improbable that some young Arcelle, covered with the same kind of filmy envelope or rudimentary test, are capable of undergoing similar mutations. Forms are sometimes met with which it is difficult to interpret on any other hypothesis. The Diffugix, as previously stated, have, in most species, sand-grains and other substances selected from the surrounding medium, superimposed upon a secreted membranous base. Experiments have been made from time to time, by Continental naturalists, upon these structures, with results which are both interesting and suggestive. Verworn (1888) directed his attention INTRODUCTION. 19 and experiments to a typical Difflugia, D. uiceolatu, conjointly with the marine Polystomella, in order to ascertain the relation of the plasma-body in each case to the shell-structure and the behaviour of the animals under artificial conditions. The body of an individual Difflugia, a portion of whose shell had been removed, was found to be charged with sand-grains, some lying apparently only adherent to, but others completely immersed in, the protoplasm.* Biitschli had some years previously, says this author, intimated the pro- bability that the foreign material employed in the construction of the Difflugian shell was taken up into the protoplasmic body of the animal itself, and subse- quently deposited at the surface.t And Gruber, adopting this suggestion, and with reference to the frequently-observed phenomenon that other Rhizopods take up sand-grains, said: “ Scarcely any doubt will remain that Biitschli’s opinion with regard to the Difflugian shell is correct, and consequently these animals themselves will select and take up into them- selves from the water the material—the sand, the Diatomaceee, or whatever it may be. They thus pro- ceed to divide themselves, and the formation of the new shell takes place in the same way as in Huglypha, Quadrula, and other Monothalamia.” In order to verify these conclusions, Verworn, in the first place, ascertained the fact of the inception of sand-grains. Finely-powdered dark blue glass was introduced into the water with living Difflngix, but it was disregarded by the animals until a clumsy, entomostracan (Cypris) came near a Difflugiu, and pushed roughly against its pseudopodia. In a few seconds the surface of the widely-extended pseudo- podia became wrinkled and knobbed, and some particles of ground glass were observed adhering to them. They were gradually absorbed completely into the interior of the shell along with the pseudopodia. It * ¢Zeitschr. fiir Wiss. Zool.,” xlvi, p. 455. (Transl. in ‘Ann. and Mag. Nat. Hist.,’ 1888). + Bronn’s ‘ Klassen und Ord. des Thierreichs’ (1880). 20 BRITISH FRESHWATER RHIZOPODA. seemed evident that by mechanical irritation a “ reflex contraction” of the pseudopodia was produced, and, combined therewith, a secretion of a sticky coat on their surface, which caused the glass granules to adhere to the pseudopodia, and to be drawn in with them. By a series of experiments repeated upon other species of Difilngia, Verworn ascertained the great regularity of this process. When a Difilngia had extended its pseudopodia to a great length, and was groping about between the glass plates, it was irritated with a sharp needle; the same effect was then pro- duced with great exactness. The pseudopodia became tubercular, “and while previously no glass granules were adherent to them, these now clung firmly, and were slowly drawn into the shell. Specimens, the shells of which were partially removed, showed that the glass grains not only remained adherent to the surface of the protoplasm but were actually drawn into it. The same writer had subsequent opportunities of observing individual Difflugiz undergoing division, and found that shell-formation in a young Difflugia accorded exactly with Gruber’s observations in the case of Kuglypha alveolatu. When the protruding mass of protoplasm from the old shell had attained approni- mately the normal size, he observed that a ball of glass granules had already, in part, entered the newly- formed half, in which the protoplasm with the finely- powdered glass showed a slowly-flowing movement. In amore advanced stage of division the protr uded proto- plasm had already assumed pretty nearly the form of the Difflugian shell (D. wrceolata), and the particles of glass had arranged themselves upon its surface. The new half seemed not yet to have a solid shell, but the glass granules were loosely fitted to one another. Upon separation from the parent the newly-formed individual was observed groping about in the water, with pseudopodia extended. The shell exhibited the characteristic form, but the pale bluish glass grains INTRODUCTION. 21 were united to each other by a narrow, transparent, and originally quite colourless, connective substance, which only some days later began to acquire a dark brownish hue. : Another result of Verworn’s experiments was to show that the Difflugian shell, once injured or removed, is incapable of restoration. The whole of the shells of several individuals were removed without injury to the protoplasmic body, and whilst the Difflugie# lived a considerable time—some of them about three weeks— and behaved quite normally, taking up sand-grains, which collected in the interior of the protoplasm, no trace of a regeneration of the shell was observed ; the body-surface did not present the least excretion or deposition of solid matter. It was “rather soft, per- formed ameeboid movements, and developed pseudo- podia”; in fact it had a strong resemblance to Pelomyzxa, the likeness being still further increased by the greyish-brown coloration, the incepted glass granules, and the great number of nuclei. The obvious conclusion is that in all the Mono- thalamia the test originates at the moment of fission and is completely finished at the separation of the new individual from the parent. The protoplasmic body then ceases to have any secretory relations with the shell: the faculty of shell-formation has ceased. Upon a review of all the circumstances, and having regard to the fact that whilst injuries to a mono- thalamous Rhizopod test cannot be repaired, in the polythalamous forms (the Foraminifera) this takes place to the fullest extent, as shown by Verworn’s experiments on Polystomella crispw and those of Carpenter on Orbitolites tenwissima and O. complanata. Dreyer, in ‘ Biologische Centralblatt’ (1889) endorsed Verworn’s conclusion that the faculty of a soft body of secreting shell-material only continues so long as the normal growth of the shell itself, from which, then, the different behaviour of the mono- and poly- thalamous Rhizopods may be explained. 22 BRITISH FRESHWATER RHIZOPODA. REPRODUCTION. Several modes of reproduction have heen observed among the Rhizopoda, but, from the infrequency of their occurrence, some have not been satisfactorily worked out. The modes most frequently noticed are— (1) simple fission or binary self-division; and (2) spore- formation. The latter is little more than the breaking up of the plasma into fragments, and the development of these; each separate portion being the germ, or earlest stage in the existence, of a new individual. This process is usually preceded by the encistment of the adult individual ; that is to say, the formation, upon the withdrawal of the plasma into the interior of the test (in the Conchulina) of a spherical or oval cist, which acquires a hard (chitinous or possibly siliceous) coat. The cist remains quiescent for a longer or shorter period, until division of the plasma and nucleus takes place, and the “spores” are liberated. Fre- quently—but, according to Ray Lankester, not neces- sarily—two (rarely three or more) individuals come together and fuse before breaking up into spores. This process is known as “conjugation”; and there can be no doubt, says the same authority, that the physiological significance of the process is similar to that of sexual fertilization, namely, that the new spores are not merely fragments of an old individual, but are something totally new, as they consist of the substance of individuals which previously had different life- experiences. Whilst spore-formation is not necessarily preceded by conjugation, conjugation is not necessarily followed by spore-formation. Professor Lankester further remarks: “There is certainly no marked line to be drawn between reproduction by simple fission, and reproduction by spore-formation ; both are a more or less complete dividing of the parent protoplasm into separate masses; whether the products of the first fission are allowed to nourish themselves and grow INTRODUCTION. 23 before further fission is carried out, or not, does not constitute an essential difference.” * Calkins remarks that while the majority of the Protozoa reproduce asexually, as described, reproduc- tion in some is bound up with complete sexual differen- tiation, and a series of forms may be selected which indicate the probable development of the sexual from the more primitive methods. In numerous cases the sexual phenomena include many of the preliminary maturation stages shown by the Metazoa, in the forma- tion of polar bodies and reduction of the quantity of chromatin, ete.t Blochmann asserted that “copulation,” in which the plasma-bodies of two animals become completely fused together to form a new individual, as well as “conjugation,” in which the animals, after long-con- tinued union, separate again from each other, and in which hitherto no demonstrable changes have been observed, actually occur. In all cases of fission it 1s important to note the part, in the process, which is taken by the nucleus. Invariably the first signs of division are to be noted in this organ; the separation of the protoplasm, with its contents, into two equal parts, follows, and one half of the nucleus goes to complete the organisation of the new individual. This is, briefly stated, the process observed in the Amcebina. In the testaceous forms the process is essentially the same. Here division takes place by the extrusion of one half of the plasma-body through the mouth of the shell. Some remarkable phenomena have been de- scribed by Blochmann in the case of Huglypha alveolata. The protoplasm emerged from the parent-shell, and became covereil with shell-lamelle,} forming a new individual of the normal size, which received its moiety of the divided nucleus. But, after this point had been * Art. “ Protozoa” in ‘Encyel. Brit., 9th ed. +‘The Protozoa,’ p. 55. 4 t‘ Morphol. Jahrb.,’ xiii (1887), p. 173. See Transl. in ‘Ann. and Mag. Nat Hist.’ (6), vol. i (1888). 2-4. BRITISH FRESHWATER RHIZOPODA. reached he found that the process was arrested. Separation of the new individual from the parent did not take place; and not infrequently, whilst two shells and two nuclei were produced, only a single animal resulted. The plasma which filled the newly-formed shell was retracted again into the old one, whilst one of the nuclei was thrown off, and perished. The purpose seems to have been accomplished of ridding the parent of its superfluous shell-lamelle and of a part of its nucleus; but what the precise significance of the act may have been otherwise, is not apparent. On the other hand it may be assumed that new Fig. 12.—Stages in the reproduction (division within the test) of Microgromia socialis (after Archer). x 500. individuals are constantly being formed, in many, pro- bably all, of the shelled Rhizopoda, as theresult of perfect fission, one half of the divided nucleus always going to the daughter cell. In some testaceous species complete division takes place within the shell. The daughter individual, fur- nished with nucleus and contractile vacuole, migrates in the amceboid state, secretes a shell for itself, and may either follow an independent existence or unite with the parent to form part of a colony (e.y. Miero- gromin socialis, Raphidiophrys vividis), A form of division called “budding” has been noted in the Areclle and some Difflugivz. A plasma “ bud” INTRODUCTION. 25 forms outside the shell-mouth of the parent, and this bud grows, until, having acquired a size approximate to that of the parent, a chitinous test is secreted, and the “bud” falls off and pursues an independent existence. Several “buds” may be formed by a single individual at the same time. Fig. 13.—Early stage in the conjugation of Diflugia pyriformis, var. lacustris: two individuals approaching each other, the plasma of the one enveloping the oral aperture of the other, and the granular substance of the two animals commingling. A few minutes sufficed to bring the mouths of the tests close together. x 200. The cysts, so commonly observed in the testaceous Rhizopoda (Nebelu, Difflugia, Englypha, etc.) protect what are known as “swarm-spores.” The parent organism splits up into separate cells, each cell pro- vided with its portion of the nucleus, and also, on liberation, with means of locomotion, which may be Fie. 14.—Late stage in the conjugation of Nebela collaris: two tests closely adhering, one filled with protoplasm, the other nearly empty. In the latter the remaining protoplasm con- tinued to be attached to its test by numerous protoplasmic threads. x 250. flagella or pseudopodia. These either undergo subse- quent fission or develop at once into the typical form. _Encistment is probably preceded by the conjugation (“copulation,” Blochmann) of two individuals. It has been observed in many testaceous forms. Individuals in pairs, having the mouths of their tests closely 26 BRITISH FRESHWATER RHIZOPODA. adhering, are of frequent occurrence. Where the tests are sufficiently transparent, a streaming of the proto- plasm may be observed from one shell into the other (ve. y. Huglypha, Cyphoderia), slow but continuous, until one shell is entirely emptied. The pair will remain attached for a considerable time, and it is presumed that after separation the encistment of the united protoplasm, in the test which contains it, is completed, there to undergo subsequent division and to produce “ swarmi-spores. ” Vampyrella is said to reproduce while encisted, by dividing into a number of parts, each of which emerges provided with pseudopodia like those of the parent. It has been observed, however, in the case of V. lateritia, that young amceboid forms escape from the parent and pursue a separate existence, first as amcebule. ‘These are liable to be mistaken, without careful scrutiny, for actual Amobe. At the time of, and immediately subsequent to, extrusion, they have sharply-pointed pseudopodia ; but after a while the pseudopodia become blunt, completing the resemblance to some of the smaller forms of Ameba jroteus and even of Dactilo- spherium vadiosum. Their after-development has not been traced with certainty, but it is assumed, no doubt with good reason, that in a short time these off-shoots, or plasma-spores, of the Vampyrella develop into mature individuals. They are destitute of any flagellum. In Pelomyea, again, spore-formation, divergent in form, but probably not in substance, from the general type, has been noted. This organism is multi-nucleated, the nuclei being small and distributed throughout the plasma-body. An individual was observed by Greeff to liberate a number of amcebulee, which he thought might be its spore-like young. The animal at first seemed as if in the act of breaking up. Around the whole outer margin of the Pelomyra there came forth an incalcul- able number of minute amoebule, surrounding the parent body in a thick annularly-arranged crowd. These had all the same habits, movements, and size ; INTRODUCTION. 27 and showed also a nucleus and nucleolus, and a con- tractile vesicle, the latter mostly posterior.* Gradually these bodies settled down. In place of the vigorous amceboid contractions of the whole body, merely hyaline lobes or finger-like processes were extended ; as they contracted one by one into a globular sub- pyriform figure, a resting-state set in; then a long vibrating filament was projected from the body, and the metamorphosis of the amcebula into a flagellate spore was complete. The author did not follow their development further. They were not, he considered, in any sense parasitic, but had their origin in the peculiar “shining bodies” (glanzkorper) which occur in large numbers, along with the small nuclei, in the plasma-body of Pelomyxa. These shining bodies are of roundish, ovoid, or irregular figure, and glossy appear- ance. In an individual not very highly charged with extraneous matter they may readily be detected. From these remarks it will be seen how diverse are the forms under which reproduction takes place in the simple-celled Rhizopoda. The Heliozoa present no essential difference; but these will be more con- veniently dealt with under their own proper head. It may not be out of place to allude here to the theory of Weismann and others of the “ deathlessness ” of the Protozoan cell, thus expounded by Prof. Ray Lankester: + “ It results from the constitution of the Protozoan body as a single cell, and its multiplication by fission, that death has no place as a natural re- current phenomenon among these organisms. Among the Enterozoa certain cells are separated from the rest of the constituent units of the body as egg-cells and sperm-cells ;~these conjugate and continue to live, whilst the remaining cells, the mere carriers as it were of the immortal reproductive cells, die and disintegrate. There being no carrying cells which surround, feed, and nurse the reproductive cells of Protozoa, but the * © Arch. f. Mikr. Anat.,’ x, p. 51. + “Protozoa,” in ‘Encyclopedia Britannica, 9th ed. XIX (1885). 28 BRITISH FRESHWATER RHIZOPODA. reproductive cell being itself and alone the individual Protozoan, there is nothing to die, nothing to be cast off by the reproductive cell when entering on a new career of fission... . Experiment and observation in this matter are extremely difficult, but we have no reason to suppose that there is any inherent mit to the pro- cess of nutrition, growth, and fission, by which con- tinuously the Protozoa are propagated. The act of conjugation from time to time confers upon the proto- plasm of a given line of descent new properties, and apparently new vigour. Where it is not followed by a breaking-up of the conjugated cells into space, but by separation and renewed binary fission (Ciliata), the result is described simply as ‘ rejuvenescence.’ ” This theory, which Ehrenberg first suggested, seems to us to be based upon insufficient data. The available evidence is directly opposed to such a supposition as the immortality of living matter in any form. The protoplasmic cell does “ die and disintegrate.” Oppor- tunities for observation, it is true, are rare. One, within our own experience, may be worth placing on record here. During an examination of pond-water an Aimaba entered the field of view, in the condition represented in figure 15a. The main body was advancing in Ameba fashion by lobular expansions anteriorly, but dragging behind a trail of its own protoplasmic substance. This was clearly an abnormal condition, and in endeavouring to account for it one was led to suppose that the organism had somehow met with an accident by which its body had been so torn as to form a kind of tail with a terminal bulb, about midway between which and the main body there was a slight thickening. Curiosity led us to keep the animal under observa- tion for about an hour and a half. During that period the terminal bulb became separated and assumed a spherical shape: (-); afterwards the middle portion separated; and at last the main body ceased to show any indication of life, and rounded out into a spherical INTRODUCTION. 29 ball. There were, therefore, three portions of proto- plasm of different sizes representing the original organism. Whilst under the microscope they went through the successive phases represented, until, finally, the larger sphere burst, as the smaller one had done before it, and its granular contents were dispersed. There was no indication of life in any of the dispersed granules, and all that remained of each spherule was a ring of hardened ectoplasm. That this was a case of spore-dispersion is beyond the region of possibility. Fig. 15.—Stages in the dissolution of Ameba proteus. a, Con- dition of the living individual as first seen; b, c, fragments of protoplasm which became detached from the main body ; d, the larger of the two fragments burst and the contents dispersing ; e, f, g, stages in the dissolution of the main body; at g the body has finally dissolved, leaving only a ring of hardened ectoplasm. x 150. The death of a Protozoan being so speedily followed by disintegration, it is not surprising that but few opportunities should occur of witnessing it. Distrisution, Hasrrats, ETC. The Rhizopoda are cosmopolitan. There is no quarter of the globe destitute of them, and whilst climate may favour an exuberance of certain forms, it is a curious fact that many which are familiar to us, in these islands, are quite as plentiful, varying hardly at all im struc- ture, in such widely separated regions as America and 30 BRITISH FRESHWATER RHIZOPODA. Australia. Clathrulina elegans is mach more abundant in the waters of Pennsylvania than with us, and Lec- quereusia spiralis 18 as common in swampy places in the Far West, and in New South Wales, as in the Sphag- num-bogs of Britain. The Difflugias, Hyalosphenias, Nebelas, and Heleoperas, the crystalline Quadrila vul- garis, the Euglyphas, and many others, occur in equal abundance on both sides of the Atlantic. The Rhizopoda inhabit ponds and lakes, marshes and swamps; wherever, in fact, enough moisture exists to support a tuft of moss. They are plentiful in still pools, on submerged vegetation, and in the surtace- ooze of ponds and ditches. At pond-sides, among the stems of sub-ayuatic Hypa, about the roots of Par- trande fortuna and Anlacomnium palustre, they may at all times be found. Moist dripping rocks in sub-Alpine districts and near the coast, in tufts of Parbulu and similar mosses; and the walls of aqueducts, where frequently there is a percolation of water through crevices of the masonry, sometimes yield the very rare species. They nestle in the foliage of mosses and hverworts, and among the masses of Conferva and other lowly vegetation which affect such situations. The Rhizopoda in these localities are not infrequently associated with such diatoms as Campylodiscus clipeus and Asterionella formosa, besides numerous Desmidian forms. Difflugia constrictu, D. globulosi, and often D. avenla, with some forms of Arcella, find sufficient moisture to sustain life im tufts of moss growing on the trunks of trees and about their roots in shady woods. Various Amahe, Pelomywva, and most of the Arcelle, as well as Difflugix, are commonly found in ponds and ditches, and creeping about the foliage of aquatic vegetation, where they feed upon desmids, diatoms, and Algee of various kinds. The floeculent matter which invests the finely-civided leaves of Ceratophyllum, Mtriewlavia, and the aquatic Rawimenli, harbours a great variety of Rhizopod life; and some special and vare kinds, such as shuweha pilosa, should be sought for in INTRODUCTION. 31 such situations. The under-sides of the leaves of water-hles, the common Potamogeton, and other submerged plants, are likewise prolific of species. But for the finer forms of Hyulosphenia, the Nebelas, Heleoperas, etc., search must be made in Sphagnum- bogs and moorland pools. It is in such places that the rare Raphidiophrys elegans, Amphitrema (Ditrenca) flavum, and A. Wrightii were discovered by Mr. Archer, in Ireland, and there also the singular Chlamydoinyxa and the rarer Heliozoa may be looked for with success. In matters of habitat the Rhizopoda, like other creatures, have their preferences. It would be in vain, for example, to look for the beautiful Hyalosphenias, the Nebelas, or the rarer Reticularian species in the deep waters of a pool, or for Pelomyea amongst Sphagnum. Professor Penard has shown, by his inves- tigations at Geneva, that the deep waters of a lake ma contain new and unsuspected forms of life. The Amebe, Difflugie, and Arcelle seem indifferent to situation. Some of the rarer kinds may be gathered on dripping sandstone rocks among low forms of vegetation. Bogs, again, harbour the rarer species of the filose protoplasts. They are also the habitats of the naked Reticularians, Biomyxa, Gymnophrys, and Penardia, and also of Chlamydomyvra, which in its resting-state is parasitic on Sphagnum. The moss Dicranella cervicu- lata, which covers with a velvety-green mantle the sides of deep drains on peat-bogs, gives shelter to a great variety of forms, notably the delicate little Pamphagus hyalinus, as well as some of the smaller Huglyphe, Cyphoderia ampulla, Trinenva acinus, Assulina seminulum, ete. Nebela bursella is met with in associa- tion with these, but in an ill-developed state usually arising from insufficient moisture in summer. Micro- gromia occurs in colonies, mostly in shallow bog-pools, along with Pompholyzophrys, Acanthocistis, and Vai- pyrella lateritia, but not invariably so. We have met with it in sluggish streams, in masses of filamentous alge, and in ponds among the foliage of aquatic Hypi ; 32 BRITISH FRESHWATER RHIZOPODA. but in the latter situation not in large colonies—half-a- dozen individuals together being the maximum number. Usually they occur as single individuals or in pairs, or in small colonies of four or six. CoLLECTING. For the reception of pond-gatherings, squeezings of Sphaguuin and other aquatic mosses, and the often unattractive and slmy-looking alge found growing on dripping rocks, the collector of Rhizopoda should be furnished with a number of wide-mouthed bottles or test-tubes, the latter preferably, as the thinness and clearness of the glass admits of inspection in the field with a high-power lens. A vasculum is the most convenient receptacle for tufts of wet moss, Sphagium, etc., from bogs and pond- sides. It is desirable to make a note of the localities from which these are taken, in order that the habitat of any rare species which may turn up during micro- scopical examination may be noted. Provided it be kept moist, and in a growing state, the Sphaguum, etc., with the Rhizopodous life which it harbours, may be preserved for weeks or months, affording material for constant study. It is desirable to bear this in mind when a summer excursion to Wales or Scotland is contemplated. A gathering of Sphagnum can be kept perfectly fresh through the winter in a garden-frame. Water, in small bottles, is apt to get foul unless some growing vegetation be kept in it. At the same time, if from a locality rich in Rhizopoda, it would be unwise to throw it away too soon. A stem of Anacharis or Callitriche introduced into a two- or three-ounce bottle of water, at the time of gathering, will keep it sweet and healthy for many weeks. In a short time the side of the tube nearest to the light will become crowded with Rhizopod life, especially with such tes- taceous forms as Arce//la and Centropyris, and with LActinosphertn or other Heliozoa. A peculiarity of the INTRODUCTION. 33 rare and curious Ciliophrys infusionwm is that, neces- sarily or otherwise, it most frequently occurs in water which has been kept two or three weeks in association with fragments of pond-vegetation. The occurrence of particular species, year by year, in the same ponds, is not, however, to be relied upon. An aquarium, in which some fine-leaved plants, e. 9. Hottonia palustris, Utricularia vulgaris, and Ranuwn- culus aquatilis, are kept growing without being often disturbed, is a valuable adjunct to the study of the Rhizopoda. PRESERVATION. By the employment of dilute nitric acid or sulphuric acid it is possible to isolate the Rhizopod nucleus; when carmine staining renders a study of that organ quite practicable. The process, however, is a delicate one. Dr. Eugene Penard has, by the exercise of much care and patience, preserved in suitable media numerous examples for reference. Where they can be made, permanent preparations are no doubt desirable and useful, inasmuch as they facilitate a study of the nuclear structure under high powers of the microscope, but the ordinary student will probably be content to make careful drawings from living examples, in different aspects and under varying conditions of their existence. These, together with descriptive notes, should in all cases be preserved. The transparent tests of some of the Conchulina, when freed from extraneous matter, may be preserved in glycerine jelly, and the gritty tests of various species of Difflugia can be mounted as opaque objects in the same manner as Foraminifera. Beautiful examples, obtained by repeated washings of the mud from a pond at Chipperfield, Herts, have been obtained by Mr. Arthur Harland, showing that this method of treating the Difflugiz is feasible and yields good results. 3 34 BRITISH FRESHWATER RHIZOPODA. CLASSIFICATION. Dusarpin* made one of the earliest attempts at a classification of the Protozoa, and in his second order of the Infusoria, in which he placed his “ Animauzx pourvus @expansions variable,’ he approached very nearly to the classification of the present day. The three families into which he divided this order— Amibiens, Rhizopodes, and Actinophryens—corres- pond closely with (1) the Ameebina, (2) the Conchu- lina and Foraminifera, and (3) the Heliozoa. More- over he grouped his three families into two sections, placing the Amibiens and Rhizopodes in one, and the Actinophryens in the other, as we now differentiate the Rhizopoda from the Heliozoa. Later, von Siebold + divided the Protozoa into two classes, the Rhizopoda and the Infusoria, the former including the above three families of Dujardin. This obviously natural primary division served for a time; but advancing knowledge rendered further systematization indis- pensable. Four classes or main groups of Protozoa are now generally recognized, namely, the Sarcodina (with the Heliozoa), at the bottom of the scale; the Mastigo- phora or flagellates ; the Sporozoa; and the ciliated Infusoria. The inter-relations of the Sarcodina, the only class with which we are now concerned, remain more or less uncertain. Obscurity surrounds the life- history of many forms, rendering a perfect division into genera and species for the present impracticable. Haeckel separated the (supposed) non-nucleated forms from the nucleated, or those in which the existence of a nucleus had been demonstrated, in order to establish * «Hist. Nat. des Zoophytes. Infusoires,’ 1841, p. 126. + ‘Anatomie der Wirbellosen Thiere,’ 1848, p. 3. CLASSIFICATION. 35 a class, the Monera or Homogenea, regarded by him as occupying a lower plane in the evolution or differ- entiation of structure. Others, notably Biitschh, con- sidered a merely negative distinction valueless, and subsequent investigation has confirmed their judgment. The presence of nuclei or nuclear substance, in some form, has been demonstrated in many species where formerly it was not suspected. Assuming Biitschli’s dictum to be well grounded, that “the nucleus needs the plasm and the plasm the nucleus,” in the develop- ment of a perfect organism—that the activities of both are reciprocal, and one without the other cannot live, a conclusion strongly deducible from all that has been ascertained regarding their vital functions— Haeckel’s separation of the apparently non-nucleated forms from the general group seems unwarranted, and his term “Monera,” and also “ Homogenea,” should disappear. Professor Lankester describes the substitution, in his genus Archerina, of a chlorophyl-coloured capsule for the nucleus proper,—it is representative, in fact, of the nucleus,—and whilst refraining from the assertion that no existing Protozoa are devoid of nucleus, corre- sponding in this character with the non-nucleated Protophyta (e.g. Bacteria), he found the inclusion, in his proposed system of classification, of the Homo- genea, impracticable, and chose to defer taking that step until it had been conclusively shown that forms now regarded by some as homogeneous (Biomyea, Gymnophrys, etc.) are really so. The general relations of these apparently non-nucleated forms with the nucleated most nearly allied to them cannot be ignored in any systematic arrangement. And, it may be added, in any case the form of the nucleus, when present, is of little specific value. The arrangement here adopted is, in its main features, on the lines now most generally accepted by Continental authors, whose long-sustained and fruitful investigations entitle them to respect. 36 BRITISH FRESHWATER RHIZOPODA. CLASS SARCODINA. Protozoa naked or testaceous, possessing, in matu- rity, digitate, lobose, finely reticulate, or radiate pseudopodia, the latter with or without axial filaments. Reproduction by spore-formation or simple division. “ SUB-CLASS RHIZOPODA. Naked or testaceous Sarcodina, with pseudopodia of the lobose, digitate, acicular, or reticulate types. Adult forms amceboid; young (spores) amceboid or flagellate, produced by cell-division during life or following encistment. In some forms (e.g. Vampyrella vorav) individuals fuse to form plasmodia. Order I. AM(IBINA. Plasma-body naked. Family 1. Lozosa. Naked Rhizopods with lobose, or more or less digi- tate, elongate, sharply pointed or blunt pseudopodia, or with wave-like or hernia-like expansions of the ectoplasm. Genera: (1) Ameba, (2) Dactylospherium, (3) Masti- gameba, (4) Pelomywa, (5) Lithameba, (6) Ouraneba. Family 2. Rericunosa. Naked Rhizopods with filamentous anastomosing pseudopodia. Genera : (7) Gymnophrys, (8) Biomywra, (9) Penardia, (10) Chlamydomyva. Family 38. VaMPYRELLIDA. Naked Rhizopods with amoeboid movements and variable pseudopodia, sometimes radiate, simulating CLASSIFICATION. 37 those of the Heliozoa; and with one or more usually- obscure nuclei. Genera: (11) Vampyrella, (12) Hyalodiseus, (18) Nuclearia, (14) Archerina. Order II. CONCHULINA. (Testacea,* Max Schultze.) Rhizopods furnished with a test, of variable shape and construction. Family 1. -ARcBLiipa. Test chitinous, with or without extraneous matter adhering; monothalamous ; nucleus single or multiple ; contractile vacuoles one or several. Genera: (15) Arcella, (16) Pseudochlamys, (17) Centropysis, (18) Difflugia, (19) Pontigulasia, (20) Difflugiella, (21) Lecquereusia, (22) Nebela, (28) Hya- losphenia, (24) Heleopera, (25) Quadrula, (26) Cochlio- podium, (27) Leptochlamys, (28) Phryganella. Family 2. EvenypHina. Test homogeneous, or composed of chitinous or siliceous plates often of geometrical pattern; spinous or naked. Pseudopodia filose, sharply pointed, simple or branched, but not anastomosing, of variable length, emitted from the mouth of the test. Genera: (29) Huglypha, (80) Placocista, (31) Assu- lina, (82) Cyphoderia, (83) Trinema, (84) Corythion, (35) Sphenoderia, (36) Canvpascus, (87) Pamphagus. Family 3. Gromirna. Test membranous, pellucid, rarely covered with ex- traneous matter; with a single aperture. Pseudopodia long, branching, straight, or irregularly dendroid, fre- quently anastomosing. * Pre-occupied in Mollusca. 38 BRITISH FRESHWATER RHIZOPODA. Genera: (88) Pseudodifflugia, (89) Diaphoropodon, (40) Microgromia, (41) Gromia, (42) Lieberkuhiia. Family 4. AMPHISTOMINA. Filose Rhizopods with membranous chitinoid tests which have pseudopodial openings at opposite poles. Genera: (43) Diplophrys, (44) Amphitrema. (39 ) CLASS SARCODINA. SUB-CLASS RHIZOPODA. Order I. AMCBINA. Family 1. Lososa. Naked Rhizopods, with lobose, or more or less digi- tate, elongate, sharply pointed or blunt pseudopodia, or, in place of these, and serving the purpose of loco- motion, wave-like or hernia-like expansions of the ectoplasm. SYNOPSIS OF THE GENERA. Plasma-body naked (in one species clothed with fine spicules) ; in size very variable; pseudopodia digitate and extensile, or taking the form of lobate, wave-like, or hernia-like expansions ; nuclei one or more (usually single); contractile vacuole mostly single. 1. Amwba. Pseudopodia radiate, rigid when at rest, often for considerable periods, widely extensile, blunt at the apex and linear, or tapering to a fine point; straight or curved, sometimes bent at an angle, or spirally twisted. Uninuclear. Contractile vacuole usually conspicuous. 2. Dactylospherium. Flagellate, the single flagellum extended in front during progressive movement of the individual; the plasma-body and pseudopodia, in adult examples, habitually covered with fine, hardly perceptible bacilli- form spicule, or naked. Uninuclear. 3. Mastigameba. Plasma-body naked, multinucleate ; contractile vacu- oles inconspicuous ; pseudopodia lobular or wave- -like, 40 BRITISH FRESHWATER RHIZOPODA. occasionally digitate, and, in the resting phase of the organism, persistent. 4, Pelomyxa. Body discoid, pseudopodia lobose (hernia-like) ; endoplasm containing numerous minute reniform con- cretions ; nucleus large, punctate. 5. Lithameba. Amoeboid ; the plasma-body furnished at the pos- terior extremity with numerous straight, usually arti- culate, protoplasmic filaments. 6. Ourameba. Genus 1. AM@BA Ehrenberg, 1832. Volvox (pars) Linnaus Syst. Nat. ed. 10, I (1758), p. 820. Chaos (pars) Linnzus Syst. Nat. ed. 12, I, pt. 2 (1767), p 1326 Vibrio (pars) O. F. Mitten Verm. Terr. et Fluv. I (1778), p. 45. Proteus (pars)'O. F, Minirr Animale. Infus. (1786), p. 9. Non Proteus Baxer Empl. Micr. (1753), p. 260. Amiba (pars) Bory pu Sr. Vincent in Dict. class. Hist. Nat. I (1822), p. 261. Anveba (pars) Exrensera in Abh. K. Akad. Wiss. Berlin, 1831 (1832), p. 79; and Infus. (1838), p. 126. Plasma-body normally a soft irregularly-spherical or ovate particle of animated protoplasm, having one or more nuclei and pulsating vacuoles, but otherwise struc- tureless,and without any apparent investing membrane; possessing inherent extensile and contractile power. Locomotion effected by lobular expansions or extensions of the hyaline ectoplasm, originating on any part of the body-surface, and forming in some species broad lobes, in others digitate processes, short or elongated (some- times branching), active or rigid, blunt or sharply-_ pointed. Hndoplasm granular, semitransparent, in some rare examples nearly opaque. In the quiescent (encisted) state, according to Leidy, the body is purged of food and other ingested matter, and becomes uniformly globular or elliptic, and invested with a structureless membrane. Individuals differ greatly in size as well as in vital activity, but all have the same plastic body, more or AMC@BA. 4] less transparent, and susceptible of constant change, the result of pseudopodal action. The pseudopodia are never elongated and rigid, as in the resting-phase of Dactylospherium radiosum. From the genus Pelo- myzxa, with which they are apt to be confounded, the Amobe differ in possessing usually but a single nucleus, all the known British Pelomyze being multi- nucleated, much larger, and more slug-like in move- ment than the largest Amabe, and also more opaque from the inception of large quantities of inorganic matter. 1. Ameba proteus (Pallas) Leidy.* (Plate I, figs. 1-6; Pl. IIT, fig. 2; and fige. 2, 5, 6, and 15, in text.) Der kleine Proteus Rosut Insecten-Beliist. (1755), p. 621, t. ci. Volvow chaos Linnaus Syst. Nat. ed. 10, I (1758), p. 821. Volvoxw proteus Patias Elench. Zooph. (1766), p. 417. Chaos protheus Linnmus Svst. Nat. ed. 12, I, pt. 2 (1767), p. 1826. Vibrio proteus O. F. Mttter Verm. Terr. et Fluv. I (1773), p. 45; Guztin Linnei Syst. Nat. ed. 13 (1788), p. 3899. Proteus difluens O. F. Mttter Animalc. Infus. (1786), p. 9, t. i, ff. 1-12; Apams Ess. Mier. (1787), p. 477, t. xxv, ff. 2,3; Bory pm Sr. Vincenr Vers, I (1791), p. 2, t. i, f.1, in Tabl. Encycl. Méth; Lamarck Syst. Anim. s. Vert. (1801), p. 596, and Hist. Nat. Anim. s. Vert. I (1815), p. 416; Scuranx Fauna Boica, III (1803), 2, p. 24; Buarn- VILLE in Dict. Sci. Nat. (1826), p. 398; Hozven Handb. Dierk. I (1828), p. 50; Svarx Elem. Nat. Hist. 1I (1828), p. 450; PrircHarp Animalc. (1834), p. 36, t. i, ff. 8-12. Proteus crystallinus Scurank Fauna Boica, III (1808), 2, p. 24. Amiba divergens Bory pr St. Vincent in Dict. class. Hist. Nat. I (1822), p. 261. Amiba Reeselit Bory pu St. Vincent Zooph. (1824), p. 46, in Encycl. Méth.; Dusarprin Infus. (1841), p. 282. * The synonymy is not exhaustive, but it is hoped that it may be found useful as indicating most of our sources of information on the various species and their distribution. In a few cases the first and last or even only one edition of a work is quoted, and some inferior illustrations in recent works are not referred to. 42 BRITISH FRESHWATER RHIZOPODA. Amiba Mulleri Bory pr Sr. Vincent Zooph. (1824), p. 46, in Encycl. Méth. Ameba diflwens Exrunsrre in Abh. K. Akad. Wiss. Berlin, 1830 (1832), pp. 39, 61, 78, t. i, f. v; op. cit. 1831 (1832), p. 79; and Infus. (1838), p. 127, t. viii, f. xii; BuarnvILie Man. d’Actinol. (1884), p. 623; Rymuer Jones Anim. Kined. (1841), p. 54, f. 16, and in Todd’s Cyclop. Anat. IV, 1 (1847), p. 10, f. 6, nos, 7-138; Scumarpa Kleine: Beitr. Naturges. Infus. (1846), p. 830; Briaurwztt Fauna Infus. E. Norfolk (1848), p. 29, t. xi, f£. 3; Srepotp Anat. wirb. Thiere (1848), p. 20, and (Engl. trarsl.) Anat. Invert. (1854), p. 830; Prircnarp Hist. Infus. (1842), p. 166; new ed. (1852), p. 202; and ed. 4 (1861), p. 549; Perry Kenntn. kleinst. Lebensf. (1852), p. 188; Coznz in Proc. Essex Inst. I (1853), p. 45; Owzw Invert. Anim. ed. 2 (1855), p. 25; Honven Handb. Zool. (Engl. transl.) I (1856), p. 46, t.1, f. 2; and Atlas Leerb. Dierk. (1865), p. 7, t.1, £1; Prcx in Verh. Vereins Wien, VII (1857), p. 36; Hoge Microsc. ed. 8 (1858), p. 266, f. 163, to ed. 1882, p. 378, f. 206; Gossz Ev. Microsc. (1859), p. 459, f.; Enartmann in Arch. Néerl. [V (1869), p. 434; Mace in Rend. R. Ist. Lomb. (2) IX (1876), p. 440, etc., and op. cit. (2) XXI (1888), p. 8308; Gnza in Herausg. Nat.-Mus. Budapest, I (1877), p. 166; Carranzo in Boll. Scient. I, an. 1 (1879), pp. 7, 57; an. 3 (1882), p. 116; and op. cit. III, an. 10 (1888), pp. 91, 96; Parona in Boll. Scient. I, an. 2 (1880), p. 24, and an. 4 (1882), pp. 51, 56; Locxwoon in Amer. M. Micr. Journ. VI (1885) p. 46; Saccui in Boll. Scient. III, an. 10 (1886), p. 41; Cunzo in Boll. Scient. III, an. 12 (1888), p. 117; Frunzen Mikr. Fauna Argent. I, Prot. 1 (1892), p. 122, in Bibl. Zool. IV ; Lonai in Atti Soc. Ligust. VI (1895), p. 67. Amaba princeps Enrensrra in Abh. K. Akad. Wiss. Berlin, 1831 (1832), pp. 28, 79; Infus. (1838), p. 126, t. viii, f. x; and in Ber. K. Akad. Wiss. Berlin, 1853, p. 255; Prircuarp Hist. Infus. (1842), p. 165, t. ii, ff. 85-87; new ed. (1852), p. 201, t. ii, ff. 85-87; and ed. 4 (1861), p. 549, t. xxi, f. 4; Scomarpa Kleine Beitr. Naturges. Infus. (1846), p. 80; Baztzy in Smithson. Contrib. II (1851), Art. 8, passim; Prrry Kenntn. kleinst. Lebensf. (1852), p. 188; AunRBacu in Zeits. f. wiss. Zool. VIT (1856), p. 407, t. xxii, ff. 1-10; Carpenter Microsc. (1856), p. 465, f. 191; to ed. 5 (1875), p. 478, f. 252; and Foram. (1862, Ray Soc.), p. 24, t.i, f. 16; t. iv, £. 6; Pick in Verh. Vereins Wien, VII (1857), p. 36; AM@BA PROTEUS. 43 Rymer Jones Anim. Kingd. ed. 3 (1861) and ed. 4 (1871), p- 19, f. 8; Carrer in Ann. Nat. Hist. (83) XII (1863), p. 30, t. ui, ff. 1-5; and op. cit. (3) XIII (1864), pp. 19, 25 ; Carus Handb. Zool. II, Prot. (1863), p.591; Greerr in Sitz.-ber. Nat. Ver. Rhein]. XXIII (1866), p. 11; Parrirt in Trans. Devon. Assoc. III (1869), p. 65: SomeRvitie Molec. and Mier. Sci. II (1869), p. 14, f. 86; Tarzm in M. Micr. Journ. I (1869), p. 352, t. xvii, f. a; Lermy in Proc. Acad. Nat. Sci. Phil. 1874, pp. 14, 148; Macar in Rend. R. Ist. Lomb. (2) IX (1876), p. 443; Giza in Herausg. Nat.-Mus. Budapest, I (1877), p. 166; Carranzo in Boll. Scient. I, an. 1 (1879), p. 7, and op. cit. III, an. 10 (1888), p. 96; Du Purussis in Bull. Soc. Vaud. (2) XVI (1879), pp. 166, 325; BirscuHir in Bronn’s Thier- Reichs, I, 1 (1880), t. 1, f.1; McAtrtnu Biol. Atlas (1880), p. 17, t. ix, ff. 1, 2; Parona in Boll. Scient. I, an. 2 (1880), pp. 24, 46, 48, and an. 4 (1882), pp. 51, 56; Lanrssan Traité Zool. I (1882), p. 39, etc., f. 30; Brass Biol. Studien, I, 1 (1883), t.11 (pars), t.11; Ray Lanxuster in Encyel. Brit. ed. 9, XTX (1885), p. 842, f.iv, 4; NicHor- son Man. Zool. ed. 7 (1887), p. 74, f. 168; Biner Vie psych. in Etudes Psych. expér. (1888, 1891), p. 94, and (Engl. transl.) Psychic Life (1889), p. 5; Muisswer in Zeits. f. wiss. Zool. XLVI (1888), p. 498; Saccui in Boll. Scient. III, an. 11 (1889), p. 67; Surptzy Zool. Invert. (1893), p. 10; Kine in J. Quek. Micr. Club (2) V (1894), p. 415, t. xix, ff. 7-10; t. xx, ff. 3-5; Derace & Hérovarp Zool. concr. I (1896), p. 93, f. 95; Monti in Rend. R. Ist. Lomb. (2) XXXII (1899), p. 161. Amiba princeps Dusarpin Infus. (1841), p. 282, t.1, f. 11; Crevier in Nat. Canad. VII (1875), p. 274, £. 24. Amiba difflwens Dusarpin in Ann. Sci. Nat. (2) IV (1835), p- 353, t. x, ff. d, e, and Infus. (1841), p. 233, t.in, £1; Scuocn Mikr. Thiere, I (1868), p. 9, t. i, f. 16; Crivent & Magar in Rend. R. Ist. Lomb. (2) III (1870), p. 369; Crevier in Nat. Canad. VII (1875), p. 275, f. 25. Ameba Reselit Prircuarp Hist. Infus., new ed. (1852), p. 202, and ed. 4 (1861), p. 549. Amoeba oblonga Scumarpa in Denks. K. Akad. Wiss. Berlin, VII (1854), 2, pp. 6, 25, t. ii, f. 1. Ameba Reeselit (?) Carrer in Ann. Nat. Hist. (2) XVITI (1856), p. 243, t. v, ff. 4, 24. Amiba Kwselii (male pro Reeselii) Crevizr in Nat. Canad. VII (1875), p. 275. 7 Amexba diffluens Mace in Rend. R. Ist. Lomb. (2) IX ° 44, BRITISH FRESHWATER RHIZOPODA. (1876), p. 541 ; in Atti Soc. Ital. XIX (1876), p. 399, ete. ; and in Boll. Scient. I, an. 2 (1880), p. 387. Ameba princeps Maactin Rend. R. Ist. Lomb. (2) LX (1876), . 541, dein proteus Lerwy in Proc. Acad. Nat. Sci. Phil. 1876, p. 99; in Amer. Nat. XII (1877), p. 235; and Freshw. Rhiz. N. Amer. (1879), p. 30, t. 1, ff. 1-8; t. ii, ff. 1-13; t. iv, ff. 22-25; t. vi, ff. 18-19; t. viii, ff. 17-30; FULLAGAR in Sci. Goss. 1880, p. 204, ff. 121-124; Car- PENTER Microsc. ed. 6 (1881), p. 486, f. 289, to ed. 8 (1901), p. 742, f.577; Hircucock Synops. Freshw. Rhiz. (1881), p. 4; Brooxs Invert. Zool. (1882), p. 1, f£. 1; Nicuotson Classif. Anim. Kingd. (1882), p. 5, f. 3a, and Man. Zool. ed. 7 (1887), p. 75, f. 174; Vuspovsxy Thier. Org. Brunn. Prag (1882), p. 34, t.i, ff. 8-5; Purirrs in ‘Trans. Herts N. H. Soc. IT (1883), p. 121; Grozzr in Zeits. f. wiss. Zool. XXXVIII (1883), p. 872; op. cit. XL (1884), pp. 127, 180, t. viii, f.12; and op. eit. XLI (1885), p. 216, t. xv, ff. 48-45; Biocumann Mikr. 'lhierw. Siiss- wass. (1886), p. 10, t.i, £6; ed. 2 (1895), p. 13, t.1, £.3; and in Biol. Centralbl. XIV (1894), pp. 87, 89; Boiron in Midl. Nat. IX (1886), p. 174; Gremnwoop in Journ. Physiol. VII (1886), p. 258; op. cit. VIII (1887), p. 268, t. viii, ff. 1-7; and op. cit. XI (1890), p. 575; Wurrn- Luace in Proc. Linn. Soc. N. 8. Wales (2) I (1886), p. 499; Harvey in Amer. Nat. XXIT (1888), p. 72: Rotunston Forms Anim. Life, ed. 2 (1888), pp. 256, 899, f. 13c; Penarp in Mém. Soc. Phys. Genéve, XXXI, no. 2 (1890), p. 123; in Arch. Sci. Phys. XXVI (1891), p. 187; in Rev. Suisse Zool. VIT (1899), p. 14, t.1, ff. 1-6 ; op. cit. IX (1901), p. 237; and Faune Rhiz. Léman (1902), p. 57, ff.; Hetm in Journ. New York Micr. Soc. VIT (1891), p. 098; Herrwie Lehrb. Zool. 1 (1891), p. 149, f. 111, and (Engl. transl. ed. 1900) Man. Zool. (1903), p. 187, £. 116; Perry in Proe. Amer. Soc. Micr. XII (1891), p. 94; Vortrzkow in Zool. Anzeig. XIV (1891), p. 228; Birscun Mikr. Schéume (1892), pp. 72, 202, and (Enel. transl.) Micros. Foams (1894), p. 107; Casu in Trans. Manch. Micr. Soc. 1891 (1892), p. 48; Frenze, Mikr. Fauna Argent. I, Prot. 1 (1892), p. 22, t. iv, f. 8, in Bibl. Zool. IV ; Lorp in Trans. Manch. Mier. Soc. 1891 (1892), p. 56; Jutuirre in Amer. M. Micr. Journ. XIV (1898), p. 289; Scarewiaxorr in Mém. Acad. Impér. Pétersb. (7) XLI, no. 8 (1893), p. 5; Le Dantrc in Compt. Rend. CIX (1894), p. 1279, and op. cit, CXX (1895), p. 210; Levan- AMGEBA PROTEUS. 45 DER in Acta Soc. Fauna Fenn. XII (1894), no. 2, p. 8; Ravmerer in Arch, f. Entwick. VIT (1898), p. 169, f. 29: Srenroos in Acta Soc. Fauna Fenn. XVII (1898), no. 1, pp. 32, 85 ; Scursnt in Sitz.-ber. Ges. Miinchen, XV (1899), p. 90; in Festsch. C. von Kupffer (1899), p. 569, t. li; and (abstr.) in Amer. Nat. XXXIV (1900), pp. 332, 441; Zacwarias in Biol. Centralbl. IX (1899), p. 58; Cazxins Protozoa (1901), passim, ff. 10a, 17a, 49, and in Amer. Nat. XXXV (1901), p. 645, etc.; Issn in Atti Soc. Torino, XXXVI (1901), p. 68, and in Atti Soc. Ligust. XIT (1901), p. 146; Masrermaw Zool. (1901), p. 85, f. 27 ; G. 8. West in Journ. Linn. Soc., Zool. XXVIII (1901), p. 309, and op. cit. XXIX (1903), p. 109; Sroxe in Zeits. Allg. Physiol. I (1902), p. 209. Ameba communis Duncan in Pop. Sci. Rev. XVI (1877), p. 288, tt. v, vi. Ameba chaos Livy in Proc. Acad. Nat. Sci. Phil. 1878, p. 99. In general aspect, as well as in size, extremely variable; endoplasm colourless or greyish granular, frequently containing desmids and other chlorophyllous algze, or their remains, which have been incepted as food, also numerous refringent globules of variable size, and minute crystals of (apparently) calcium car- bonate. Body when at rest irregularly spherical, or ovoid; but in motion exhibiting a tendency to differen- tiate into anterior and posterior extremities—lobate expansions being protruded anteriorly—or to form digitate pseudopodia, which sometimes develop short lateral branches; the posterior extremity often ter- minating in a protuberance, expansion, or mulberry- like bulb. Pseudopodal movements frequently very active; at times sluggish. The contractile vesicle (usually single) situated behind the nucleus, which is ovoid, with a punctated surface, and usually large and conspicuous. Dimensions: Frequently 200 w in diameter in the globular form, 300 x 150 when ovoid; radiate or dendroid, palmate, and cylindroid forms varying from 0-5 mm. to 1 mm. according to Leidy. Elongate variety (Pl. III, fig. 2), 400-450 p. 46 BRITISH FRESHWATER RHIZOPODA. In the ooze of ponds; amongst aquatic vegetation ; also in marshes and bog-pools; abundant and univer- sally distributed. Ameba proteus was first described and figured by Rosel, under the name Der kleine Proteus, in his ‘ Insecten-Beliistigung’ (Recreations amongst Insects), 1755. This was the first introduction to Naturalists of the Rhizopoda asa class. Three years later Linneeus embodied it in his ‘Systema Nature,’ ed. 10, calling it Volvow chaos; Pallas (1766) changed the name to Volvox proteus; and subsequently, under a variety of designations, each representing, no doubt, some one of the many forms assumed by the organism, it figured in the works of Continental authors. Ehrenberg, in his ‘ Infusionsthierchen’ (1838), described the familiar large form as dimwba princeps, a name which it long retained; but Leidy, considering that d. princeps Ehrenb., and Proteus diffuens Mitller—the original Der kleine Proteus of Résel—represented one and the same animal, once more revised the nomenclature and adopted the title dnweba proteus, which is likely to be retained. Leidy remarks: ‘“ The specific name proteus (in Volroe proteus of Pallas) appears the more appro- priate, and would at the same time serve to perpetuate the name given to the animal by its discoverer.” Amwrlu proteus, in one or more of its forms, must be familiar to every student of pond-life. It is to be found in all still ponds which contain healthy vegeta- tion, either in the ooze at the bottom, about the older stems and leaves of aquatic plants, or in masses of floating alge. During active movement the pseudo- podia are usually digitate, simple or branched, of uniform thickness or tapering to a blunt apex; and the nucleus, which is invariably oval, is habitually posterior, the contractile vesicle occupying a position at no great distance behind it. Necessarily, however, during rapid movement, when the animal changes its hne of march, forming pseudopodia first on one side, then on the other, the nucleus and vesicle get widely AMG@BA PROTEUS. Al separated, and their posterior position may be tem- porarily lost. According to Penard the elliptic, discoid, punctated nucleus is characteristic of this species. In the larger examples of Amaba proteus the pos- terior ectoplasm habitually contracts, and, in doing so, forms a mass of “short digitate or mulberry-like processes.” These, however, are not permanent. They appear to be modified or latent pseudopodia, which are, so to speak, grouped together and dragged behind by the animal in its progress. In some, and those always the largest individuals, they are conspicuous. Leidy’s observations showed that they eventually get absorbed in the general mass, or, in response to some change in the creature’s motion, develop into active pseudopodia and are used as such. The endoplasm of A. proteus is usually charged with a considerable variety of extraneous material. Inter- mixed with chlorophyl-pellets there may be seen re- fringent bodies resembling oil-globules, and granules -of starch. The former are probably adventitious sub- stances, of no significance physiologically, though Leidy was of opinion that they might prove to be an intrinsic element. The starch-grains may have been incepted with the food. There are, in addition to these, minute crystals of quartz or calcium carbonate, or both, in variable quantity. Although the food of A. proteus consists for the most part of chlorophyl-bearing alge, such as diatoms and desmids, the animal, like others of its class, preys occa- sionally on other Protozoa, and even on the Rotifera. Plate I, fig. 3, and Pl. ITI, f. 2, represent a remark- able variety, distinguished by its mulberry-shaped caudal extremity and finely-granular endoplasm. In the latter there 1s no admixture of oil-like globules or other adventitious matter, but green corpuscles are present, which in all the examples met with were of uniform size and very numerous. ‘The nucleus and contractile vesicle are normally as in A. proteus, but in general aspect and mobility this form is so distinct as 48 BRITISH FRESHWATER RHIZOPODA. to raise a doubt whether it really belongs to this species. Leidy, however, figures it as a form of A. proteus (‘Freshw. Rhiz. N. Amer.’, pl. i, fig. 4), and it may for the present be distinguished as var. granulosa. It has been held that inasmuch as A. proteus repro- duces by fission, the protoplasmic body may be divided, and propagation effected by artificial severance. This we think is more than doubtful. Gruber’s investiga- tion of the nucleus and its relation to the plasm, years ago, seemed to dispose of it. Deprived of the nucleus, says this observer, the plasma cannot sustain life. “The nucleus needs the plasm; the plasm the nucleus.” Occasionally, though very rarely, an injured Ameba is met with, and the injury may result in the death of the individual. A case of this kind, which came within our own observation, has already been described (see pp. 28-29, f. 15). 2. Ameoba actinophora Auerbach. (Plate I, figs. 7-10.) Ameba actinophora Avuursacu in Zeits. f. wiss. Zool. VII (1856), p. 392, t. xx; Magar in Rend. R. Ist. Lomb. (2) X (1877), p. 316; Grouper in Zeits. £. wiss. Zool. XXXVI (1881), p. 464, t. xxx, ff. 9-17, and (Enel. transl.) in Ann, Nat. Hist. (5) IX (1882), p. 110, t. ix, ff. 9-17; Birscrir Mikr. Schaume (1892), p. 78, t. ii, ff. 8, 9, and (Engl. transl.) Micros. Foams (1894), p. 107, t. iv, ff. 8, 4; FrevzeL Mikr. Fauna Argent. I, Prot. 3 (1893), p. 89, t. vill, ff. 19, 20, and 4 (1897), p. 147, in Bibl. Zool. IV; Catxins Prot. (1901), p. 38. ? Cochliopodium actinophorum Panaro Faune Rhiz. Léman (1902), p. 188, ff. Plasma-body minute; when active resembling the smaller forms of Cochliopodinm bilimbosuwn, with a rounded outline, from one side of which two to six (sometimes more) short, simple, or branching pseudo- podia are protruded. According to Auerbach. the protoplasm is “distinctly surrounded by a double contour,” and the animal appears as if “covered by AM@BA ACTINOPHORA. 49 an envelope ” of thickened ectoplasm, which is capable of being absorbed or dissolved by the more fluent endoplasm, during pseudopodal extension, or on the assumption by the animal of a quiescent phase. In this latter phase the body becomes rounded or oval, or discoid, the granular endoplasm occupying a central position, with a translucent band of ectoplasm sur- rounding it. The animal in this condition is devoid of colour except from the presence of a few green par- ticles contained in the endoplasm. It remains quiescent for an indefinite time. Dimensions : Diameter when at rest (discoid phase), 30-40 p. In ponds, Cheshire, July, 1903. The above specific characters are those given by Gruber (loc. cit.), with whose figures our Cheshire examples essentially agree, although the ‘ double- contoured” character, said to be presented by the organism in the active state, was not apparent. The author cited remarks that the periphery, in his ex- amples, was for the most part quite smooth, and that only at one point did the animal extend a larger or smaller number of lobed pseudopodia. There was, he says, no persistent membranous structure, but “during the flow of the animal the cortical layer became amal- gamated with the rest of the sarcode.” The body became flattened, and the “cortical zone” disappeared, its place being taken by a broad border of clear ecto- plasm, which surrounded the darker and richly- granular central mass. In this state the nucleus becomes distinctly visible. Gruber, at the time he recorded his observations, considered this organism to be identical with Cochlio- podium bilimbosum Auerb., but the latter has a dis- tinctly permanent, though very supple, hyaline envelope. Penard (loc. cit.) reunites A. actinophora with the genus Cochliopodiwm, remarking that it has a smoother envelope, which is also more delicate and 4, 50 BRITISH FRESHWATER RHIZOPODA. refringent, than that of OC. bilimboswm. His figures, however (so different from Gruber’s), create a doubt as to whether the organisms described by the two authors can have been identical. 3. Amoeba villosa Wallich. (Plate II.) Ameba Watucu in Ann. Nat. Hist. (8) XI (1863), p. 287, t. vii (? excl. ff. 10 and 16). Ameba villosa WatuicH in Ann. Nat. Hist. (8) XI (1863), p. 336, t. ix, and p. 434, t. x, ff.5-9; Barxer in Q. J. Micr. Sci. VI, ns. (1866), p. 125; Grenrr in Sitz.-ber. Nat. Ver. Rheinl. XXIII (1866), p. 11; Tarsem in M. Micr. Journ. I (1869), p. 353, and op. cit. VI (1871), p. 276, f.; Gactiarpr in Q. J. Micr. Sci. XI, n.s. (1871), p. 80; Macer in Rend. R. Ist. Lomb. (2) IX (1876), p. 439; Downcaw in Pop. Sci. Rev. I, n.s. (1877), p. 233, t. vi, ff. 38-42; Lumpy Freshw. Rhiz. N. Amer. (1879), p. 62, t. u1, ff. 14-16; t. vin, ff. 1-16; Hrrcencock Synops. Freshw. Rhiz. (1881), p. 6; Grouper in Zeits. f. wiss. Zool. XLT (1885), p. 187; Lenperrerp in Proc. Linn. Soc. N. 8S. Wales, X (1885), p. 723; Waurmreteccr in Proc. Linn. Soc. N. 8. Wales (2) I (1886), p. 499; Harvey in Amer. Nat. XXII (1888), p. 72; Mapsius in Abh. K. Akad. Wiss. Berlin, 1888 (1889), 2, p. 25, t. v, ff. 59, 60; Casu in Trans. Manch. Micr. Soc. 1891 (1892), p. 46, t. ii, f. 1; Lorp in Trans. Manch. Micr. Soc. 1891 (1892), p.56; Levanpger in Acta Soc. Fauna Fenn. XII (1894), no. 2, p. 10, t.1, f.2; op. ett. XX (1901), no. 5, pp. 11, 22; and in Zool. Anzeig. XVII (1894), p. 209 ; SmitH in Trans. Amer, Micr. Soc. XTX (1897), pp. 63, 69, and in Amer. M. Micr. Journ. XVITI (1897), p. 381; Ravumerer in Arch. f. Entwick. VII (1898), p. 125; Penarp in Rév. Suisse Zool. VII (1899), p. 21, t. 11, ff. 1-8, and Faune Rhiz. Léman (1902), p. 70, ff.; G. S. Wusr in Journ. Linn. Soc., Zool. XX VITI (1901), p. 309. Anwha princeps (pars) Carterin Ann. Nat. Hist. (3) XII (1863), p. 30, ete., t. iii, ff. 1-3, 5. Trichameba hirta Fromenten Etudes Microz. (1874), p. 345, t. xxviii, f. 4. Saccaneba villosa Frunzut Mikr. Fauna Argent. I, Prot. 1 (1892), p. 9, t.i, £.4, and 4 (1897), p. 147, in Bibl. Zool. IV. AMC@BA VILLOSA. 51 In size rivalling the larger forms of Ameba proteus, sometimes attaining, according to Wallich, a diameter of one-fiftieth of an inch. The body, at its posterior extremity, has a villous discoid or lobed protuberance, which, whilst capable of modification within certain limits, 1S persistent. Its precise function, however, is not evident. In all other respects the animal closely resembles, even in the young state, the larger forms of A, proteus. The nucleus and contractile vacuole are normally in the posterior region, the former ovoid and punctated like that of A. proteus, the punctula- tions being disposed longitudinally. Locomotion is effected by lobular expansions of the ectoplasm, anterior or lateral, or by digitate pseudopodia, which may emerge on one side (with the result of altering the line of progression) or from all sides at once, when the appearance shown in Pl. II, fig. 2, is presented. The villous appendage does not appear to be affected by any pseudopodal movements. The colour of the endoplasm is usually a creamy-white, greyish in the denser parts, granular, and containing green and other corpuscles resembling those observed in A. proteus, and not infrequently also desmids and other alge. Dimensions variable; elongated examples often attaining a length of 250 uw or more. Ponds at Hampstead, 1863 (Dr. Wallich); in similar situations in Cheshire; in the Rossendale district of Lancashire (J. H. Lord); near Bingley, West York- shire (G. S. West). Ameba villosa was first detected by Dr. Wallich in India, and he published a description of it in the ‘ Annals’ (J. c.)in the year 1863. Returning to England he found it at Hampstead. We suspect, however, from Mr. H. J. Slack’s description of some examples from the last-named locality, in the ‘Intellectual Observer,’ Vol. III, p. 430, that the much larger and coarser-looking organism, Pelomywa villosa Leidy, was mistaken for it. The two species may have been 52 BRITISH FRESHWATER RHIZOPODA. present, for they are found in similar situations, and not infrequently in the same water. The villous appendage of A. villosa is capable of such modification as is shown by occasional contraction and expansion, but the villi always remain closely com- pacted, and apparently passive. Their appearance in the aggregate is that of a bundle of short threads; in this respect differing from the analogous organ in Pelomyza villosa where the villi are thicker and shorter. Apart from these features the two organisms are not likely to be confounded, as they differ widely in the important matter of internal structure. 4. Ameba gorgonia Penard. (Plate ITI, figs. 3-5.) Ameeba gorgonta Prnarp Faune Rhiz. Léman (1902), p. 78, ff. Body when in repose globular, with a variable num- ber of radiating mobile arms, outwardly extended on all sides, as represented in PI. III, fig. 3. Penard observes that this attitude of the animal is induced by exposure to light. An individual, first met with in this condition, kept some of the pseudopodal arms moving constantly, until they disappeared under a sudden wave-like emission of ectoplasm. Upon this the animal began a forward movement, dragging behind it the remaining pseudopodia (fig. 4) which in their turn also became absorbed. Afterwards the animal rapidly underwent a series of modifications. One of the forms it assumed is represented by fig. 5. Our Cheshire examples exhibited all the peculiarities of structure described by Penard. The pseudopodia were cylindrical, of uniform thickness, and rounded at their extremities, never pointed as in some forms of Dactylospherinn vadiosum. They were filled with the same granular endoplasm as the rest of the body (a feature regarded by Penard as of especial significance), AMGBA GORGONIA. 53 and differed widely from the hyaline pseudopodia of most of the lobose Rhizopods. Dimensions: Average diameter of body (fig. 3) 40-50 «5; including pseudopodia about 100 p. In long-kept Sphagnum from Dunham, Cheshire, June, 19038. In its movements this species is very rapid. It resembles, in some aspects, an exaggerated A. limaz. Within the endosare there may be observed a variable number of brilliant granules, which in the resting-phase extend along the arms, even to their extremities, together with small vacuoles and chloro- phyl corpuscles. The contractile vesicle and nucleus are small and inconspicuous; the latter is spherical. 5. Ameba striata Penard. (Plate ITI, figs. 6 and 7.) ? Ameeba striolata Pmrrty Kenntn. kleinst. Lebensf. (1852), p. 188, t. viii, f. 15; Parona in Boll. Scient. I, an. 2 (1880), . 24, inne verrucosa (pars)° Lerpy Freshw. Rhiz. N. Amer. (1879), t. iii, f. 37. Ameba striata Payarp in Mém. Soc. Phys. Genéve, XXXI, no. 2 (1890), p. 127, t. ii, ff. 81-384, and Faune Rhiz. Léman (1902), p. 127, ff.; Raumsier in Arch. f. Entwick. VII (1898), pp. 123, 191, 262, ff. 38, 39, 66. Body compressed, ovoid, narrowed and rounded posteriorly, but not exhibiting any caudal bulb or expansion. The nucleus round, posteriorly situated, a little in advance of the contractile vacuole, which attains a considerable size and is pellucid or pale bluish. The anterior region, when the animal is moving actively, consists of a broad expansion of clear ectoplasm. A characteristic feature of this organism is the presence of a series of delicate longitudinal lines (usually four) on the surface of the ectoplasm, which appear and disappear with the movements of the animal, indicating, in the opinion of Dr. Penard, the existence of an extremely fine pellicle. 54 BRITISH FRESHWATER RHIZOPODA. The animal makes a slow but continuous advance, and during its movements the semi-fluid endoplasm flows longitudinally, in distinct streams, modifying, by pressure, the form of the contractile vacuole, which at one moment may be circular and the next elongated or irregularly outlined. The endoplasm is finely granular, colourless, or tinged with green from the presence of minute chlorophyl particles, and it contains also a limited number of larger granules or crystalline bodies of irregular shape. Dimensions : Length 25-451; greatest breadth an- teriorly 20-35 mu. In ponds amongst submerged vegetation, usually common. The contractile vesicle, in this species, is curiously modified by the flow of the endoplasm. Whilst changing in position but slightly, its form exhibits constant variation. It will reappear, after discharge, sometimes as two separate vesicles of small size; these gradually enlarge, and ultimately unite ; and the organ not infrequently presents an oval or distorted outline. Ameabu striata has been, by some, regarded as a young state of A. verrucosa Hhrenb. Leidy (‘ Freshw. Rhiz. N. Amer.’) so describes and figures it. Apart from the fact that it is a much smaller organism, and possessed of characters of its own, which are constant, it is rarely found in association with A. verrucosa in the adult state. : 6. Ameba guttula Dujardin. (Plate V, fig. 4.) Amiba guttula Dusarpin Infus. (1841), p. 285; Crtvier in Nat. Canad. VII (1875), p. 276. Ameba guttula Perry Kenntn. kleinst. Lebensf. (1852), p. 188, t. vii. f. 18; Prircnarp Hist. Infus. new ed. (1852), p. 208, and ed. 4 (1861), p. 549, t. xxi, f. 6; AvgrpacH in Zeits. f. wiss. Zool. (1856), p. 414, t. xxii, ff. 17, 18 ; Wiiramson in Pop. Sci. Rev. V (1886), p. 197, AMGBA GUTTULA. 5D t. xii, ff. 17,18; Czmrnyin Arch. f. Mikr. Anat. V (1869), p- 162; Tarem in M. Micr. Journ. I (1869), p. 352; Fromente, Etudes Microz. (1874), p. 347, t. xxiv, ff. 2, 3, 5; Giza in Herause. Ungar. Nat.-Mus. Budapest, I (1877), p. 165; Birscu11 in Bronn’s Thier-Reichs, I, 1 (1880), t.ii, f. 3: Cooxr in J. Quek. Micr. Club, vii (1880), pp. 105, 106; Parona in Boll. Scient. I, an. 2 (1880), p- 24, and J. c. an. 4 (1882), pp. 51, 56; Saccur in Boll. Scient. III, an. 10 (1888), p. 41; Penarp in Mém. Soc. Phys. Genéve, XXXI, no. 2 (1890), p. 182, t. ili, f. 2; in Rey. Suisse Zool. VII, 1 (1899), p. 100; and Faune Rhiz. Léman (1902), p. 38, ff.; Lona: in Atti Soc. Ligust. V (1894), p. 14; Scuewiaxorr in Mém. Acad. Impér. Pétersb. (7) XLI, no. 8 (1893), p.5; Raumpier in Arch. f. Entwick. VII (1898), pp. 118, 126, 139. Amba guttula Macetin Rend. R. Ist. Lomb. (2) IX (1876), p- d41. Hyalodiscus guttula BuocumMann Mikr. Thierw. Siisswass. (1886), p. 10, t. 1, f. 8, and ed. 2 (1895), p. 12, t.i, f.1; Detace & Hrovarp Zool. concr. I (1896), p. 99. Guttulidium guttula Frenzzt Mikr. Fauna Argent. I, Prot. 4 (1897), p. 146, in Bibl. Zool. IV. In general character resembling A. limicola, but shorter and broader in proportion to the length ; during active movement ovoid and narrowed pos- teriorly, without any caudal protuberance, but in place of this with a few minute, nipple-like dentations occa- sioned by a contraction of the ectoplasm at that point. Movement effected by wave-like expansions of the ectoplasm, anterior or lateral. The granular endo- plasm contains a variable number of crystalline and other particles, and occasionally minute diatoms. The anterior ectoplasm is faintly bluish or hyaline; the whole organism is transparent; the nucleus and con- tractile vesicle are normally situated, the former rounded, but susceptible of modification. Dimensions: Length 30-35 «; breadth 20-25 u. In ponds, amongst submerged vegetation, frequent. This species was removed by Blochmann to Hertwig and Lesser’s genus Hyalodiscus, but there is really no 56 BRITISH FRESHWATER RHIZOPODA. affinity between it and the typical Hyalodiscus rubi- cundus. imeba guttula is commonly met with amongst decaying vegetation, in ponds. 7. Amoeba limicola Rhumbler. (Fig. 16.) «lmeeba limicola RuumBier in Arch. f. Entwick. VII (1898), p. 145, ete., ff. 17, 22, and in Zeits. Allg. Physiol. II (1902), p. 183; Catxins Prot. (1901), pp. 81, 85, f. 15a; Penarp Faune Rhiz. Léman (1902), p. 40, ff. Animal more or less globular, changing to oval or ellipsoid by expansions of the ectoplasm, such expan- sions being lobular, or formed by irruptions of the Fig. 16.—Ameba limicola. x about 475. internal plasma through the body-surface (hernia-lke). Nucleus as in the preceding species. Dimensions: Length 45-55; average breadth about 35 pu. Not common; occasionally met with in’ pools and sphagnum bogs. The peculiar hernia-like pseudopodia, and the broad frontal expansions of the ectoplasm, are characters which seem to justify the separation of this from the preceding and other allied species. The pseudopodium, emanating from the surface of the body, resembles a miniature eruption. Through the breach made, the granular endoplasm, in its flow, recoils on either side upon the spherical body, instead of forming a digitate prolongation. AM@BA LIMAX. 57 8. Ameba limax Dujardin. (Plate ITI, fig. 1.) Amiba limaw Dusarpin Infus. (1841), p. 235; Crevisr in Nat. Canad. VII (1875), p. 276. Ameba limax Pzrrry Kenntn. kleinst. Lebensf. (1852), p. 188, t. vii, f. 12; Prircuarp Hist. Infus. new ed. (1852), p. 203, and ed. 4 (1861), p. 549, t. xxii, ff. 4, 5; AUERBACH in Zeits. f. wiss. Zool. VII (1856), p. 414, t. xxu, ff. 11-16; Carpenter Foram. (1862, Ray Soc.), p. 25; Tarem in M. Micr. Journ. I (1869), p. 852; Trin- cHEse in Mem. Acc. Bologna, V (1875), p. 524; Gaza in Herausg. Ungar. Nat.-Mus. Budapest, I (1877), p. 165 ; Birscuu1 in Bronn’s Thier-Reichs, I, 1 (1880), t. u, f. 2; Mikr. Schiume (1892), p. 72, t.i, ff. 10, 11; and (Engl. transl.) Micr. Foams (1894), p. 106, t. ii, ff. 7, 8; Cooxz in J. Quek. Micr. Club, VI (1880), p. 105; Furtacar in Sci. Goss. 1880, p. 204, f. 184; Parona in Boll. Scient. I, an. 2 (1880), pp. 46, 48; Vespovsxy Thier. Org. Brunn. Prag (1882), p. 33, t.1,f.1; Carranzo in Boll. Scient. IIT, an. 10 (1888), p. 93; Penarp in Mém. Soc. Phys. Genéve, XXXI, no. 2 (1890), p. 124, t. ui, ff. 1-5; in Arch. Sci. Phys. XXVI (1891), p. 187; in Rev. Suisse Zool. VII, 1 (1899), pp. 18, 100; and Faune Rhiz. Léman (1902), p. 39, ff.; Zoya in Rend. R. Ist. Lomb. (2) XXIV (1891), p-. 987; Scuewraxorr in Mém. Acad. Impér. Pétersb. (7) XLI, no. 8 (1893), p. 5; Detace and Hérovarp Zool. concer. I (1896), p. 93, f. 96; Ruumpter in Arch. f. Entwick. VII (1898), p. 118 (et passim), ff. 30, 31; Catkins Prot. (1901), p. 80. Hyalodiseus limaw Buiocamann Mikr. Thierw. Stisswass. (1886), p. 10, t. i, f. 4, and ed. 2 (1895), p. 12, t. 1, £.2; Issex in Atti Soc. Ligust. XII (1901), pp. 146, 149; Levanver in Acta Soc. Fauna Fenn. XX (1901), no. 6, p. 5. Saccameba limaw Frenze, Mikr. Fauna Argent. I, Prot. 4 (1897), p. 147, in Bibl. Zool. IV. Body elongated, slug-lhke, narrowed at the posterior extremity, where the plasma is more concentrated and rough, with a rounded protuberance, which in rapid movement develops a radiating fringe of very delicate substance. This fringed protuberance Penard regards as distinctive of the species. The body broadens 58 BRITISH FRESHWATER RHIZOPODA. anteriorly, and the animal moves forward in an almost direct line, having a wide frontal margin of clear ectoplasin. The nucleus and contractile vesicle are in the posterior region, the latter usually in advance, and the endoplasm contains, besides food-particles, a variable number of minute crystalline bodies. Dimensions + Length 50-60; average breadth about 15 Me In ponds, etc., with Amaba guttula, and generally as plentiful. This species is more active than Amoeba guttula. Its mode of progression approaches that of some forms of A. proteus and A. villosa, but it is more uniform, and Penard points out its peculiar habit of changing the direction of its march by a movement of the anterior portion of the body en inasse, to right or left, whilst the posterior remains stationary. This habit is cer- tainly rare amongst the Amebe. 9, Ameba verrucosa Ehrenberg. (Plate V, figs. 1-3.) Ameha verrucosa Kurenperc Infus. (1838), p. 126. t. viii, f. xi; Prircuarp Hist. Infus. (1842), p. 166; new ed. (1852), p. 202; and ed. 4 (1861), p. 549; Prrry Kenntn. kleinst. Lebensf. (1852), p. 188; Scumarpa in Denkr. K. Akad. Wiss. Wien, VIL (1854), 2, pp. 14, 25; Carrer in Ann. Nat. Hist. (2) XX (1857), pp. 37, 40, t. 1, ff. 12,18; Pick in Ver. Vereins Wien, VII (1857), p. 36; Carpewrer Foram. (1862, Ray Soc.), pp. 36, 39, t. iv, £.8; Rymer Jonus Anim. Kingd. ed. 4 (1871), p. 20; Fromenrer Etudes Microz. (1874), p. 348, t. xxix, f. 7; Lemy in Proc. Acad. Nat. Sci. Phil. 1874, p. 167; op. eit. 1876, p- 198; op. cit. 1878, p. 158; and Freshw. Rhiz. N. Amer. (1879), p. 53, t. ii (excl. f. 37); Macar in Rend. R. Ist. Lomb. (2) IX (1876), p. 441; Carraneo in Boll. Scient. I, an. 1 (1879), pp. 7, 27, 57; op. e7t. IL, an. 10 (1888), p. 93; and in Atti Soc. Ital. XXII (1880), p- 254; Parona in Boll. Scient. I, an. 2 (1880), pp. 46, 48, and an. 4 (1882), pp. 51, 56; Huirencock Synops. Freshw. Rhiz. (1881), p. 5; Vuspovsky Thier. Org, AM@BA VERRUCOSA. 59 Brunn. Prag (1882), p. 34, t.i, f.2; Gruper in Zeits. f. wiss. Zool. XL (1884), p. 124, t. viii, f. 5, and op. cit. XLI (1885), p. 214, t. xv, ff. 89-48; Brocumann Mikr. Thierw. Siisswass. (1886), p. 10, t. i, f..7, and ed. 2 (1895), p. 18, t.i, f.4; Bozron in Midl. Nat. IX (1886), p. 174; WuirrLecce in Proc. Linn. Soc. N.S. Wales, (2) I (1886), p. 499; Fretpg in Proc. Acad. Nat. Sci. Phil. 1887, p- 122; Rottmsroy Forms Anim. Life, ed. 2 (1888). pp. 897, 899; Cxrres Cap. Horn Zool. VI (1889), Prot. p- 20; Mesius in Abh. K. Akad. Wiss. Berlin, 1888 (1889), 2, p. 27, t. v, ff. 65, 66; Saccui in Boll. Scient. III, an. 11 (1889), p. 67; Prnarp in Mém. Soc. Phys. Genéve, XXXTI, no. 2 (1890), p. 128, t. ii, ff. 35-54; in Arch. Sci. Phys. XXVI (1891), p. 187; and in Rev. Suisse Zool. VII, 1 (1899), pp. 100, 104, 107; Casx in Trans. Manch. Micr. Soc. 1891 (1892), p. 48; Loxp in Trans. Manch. Micr. Soc. 1891 (1892), p. 56; Scuznwra- KOFF in Mém. Acad. Impér. Pétersb. (7) XLI, no. 8 (1893), p. 5; Levanpzr in Zool. Anzeig. XVII (1894), p. 209; in Acta Soc. Fauna Fenn. XII (1894), no. 2, p-. ll, t. 1, f.1; op. ett. XX (1901), no. 5, pp. 11, 12; and /. c. no. 6, p.5; Loner in Atti Soc. Ligust. V (1894), p. 15, and op. cit. VI (1895), p. 70; Danczarp in Le Botan. IV, 6 (1896), p. 202, ff. 1-5; Francé in Res. wiss. Erforsh. Balat. II (1897), p. 5; Scourrretp in Proc. Zool. Soc. 1897, p. 787; Dapay Mikr. Siisswass. Ceylon (1898), pp. 4,9; Ruumsizr in Arch. f. Entwick. VII (1898), p. 116 (e¢ passim), ff. 1, 15, 25, 40, 41, 45-52, 58, 60-62, 65, t. vi, ff. a, c, F, and in Biol. Centralbl. XVIII (1898), p. 25, f. 1; Catxrys Prot. (1901), p. 218, ff. 48, 118d, 153; Issmz in Atti Soc. Torino, XXXVI (1901), p. 68; G. 8S. West in Journ. Linn. Soc., Zool. XXVIII (1901), p. 809; op. cit. XXIX (1903), p. 109; and in Ann. Scott. Nat. Hist. 1905, p. 90. Amtba verrucosa Dusarpin Infus. (1841), p. 236; Crevier in Nat. Canad. VII (1875), p. 277. Amba natans Prrry Kenntn. kleinst. Lebensf. (1852), p. 188, t. vii, f. 14. Amaba quadrilineata Carrer in Ann. Nat. Hist. (2) XVII (1856), p. 248, t. v, £38; p. 248, t. vii, f. 81; and op. cit. (3) XIII (1864), p. 19; Prircuarp Hist. Infus. ed. 4 (1861), p. 550; Carpenter Foram. (1862, Ray Soc.), p- 25; Barger in Q. J. Micr. Sci. IX, ns. (1869), p. 94; Lerpy in Proc. Acad. Nat. Sci. Phil. 1874, p. 167 ; op. cit. 1878, p. 158; and in Ann. Nat. Hist. (5) II (1878), 60 BRITISH FRESHWATER RHIZOPODA. p. 271; Parona in Boll. Scient. I, an. 2 (1880), pp. 46, 48; Saccur in Boll. Scient. III, an. 10 (1888), p. 41. Ameba terricola Greurr in Arch. f. Mikr. Anat. (1866), p. 300, t. xvili; in Verh. Nat. Ver. Rheinl. XVII (1870), p. 201; and in Biol. Centralbl. XI (1891), p. 599; Trip in Proce. Bristol Nat. Soc. n.s. IV (1870), p. 14; Gacriarv1 in Q. J. Micr. Sei. XI, ns. (1871), p. 80; Bivscwir in Arch. f. Mikr. Anat. IX (1873), p. 676, t. xxi, f. 21; Magai in Rend. R. Ist. Lomb. (2) X (1877), pp. 318, 321; Scunuiper in Compt. Rend. LXXXVI (1878), p. 1557 ; Du Puxssis in Bull. Soc. Vaud. (2) XVI (1879), pp. 166, 325; Lanugsan in Rey. Internat. Sci. VI (1880), p. 8, and Traité Zool. I (1882), p. 42; Parona in Boll. Scient. I, an. 2 (1880), p. 46; GrusER in Zeits. f. wiss. Zool. XL (1884), p. 123; BurrnoLp Stud. Protopl.-mech. (1886), p. 109; Briocumann Mikr. Thierw. Siisswass. (1886), p. 10, t.1, f. 9, and ed. 2 (1895), p. 13; Bryer Vie psych. in Psych. expér. (1888, 1891), p. 235; and (Hngl. transl.) Psych. Life (1889), p. 114; Curves Cap. Horn Zool. VI (1889), Prot. p. 20; Saccur in Boll. Scient. III, an. 10 (1889), p. 67; Herrwic Lehrb. Zool. 1 (1891), p. 149, and (Engl. transl. ed. 1900) Man. Zool. (1903), pp. 186, 189; Grirrrtas Physiol. Invert. (1892), p. 375; Loner in Atti Soc. Ligust. V (1894), p. 15; Psnarp Faune Rhiz. Léman (1902), p. 104, ff., and p. 666. Thecameba quadripartita Frommnret Etudes Microz. (1874), p. 346, t. xxxviil, f. 3. Ameba verrucosa Maaat in Atti Soc. Sct. Nat. XIX (1876), p. 407, t. ix, ff. 1-8; in Rend. R. Ist. Lomb. (2) IX (1876), p. 541; and in Boll. Scient. I, an. 2 (1880), pp. 34, 81. Ameba papillata Muruscuxowsxy in Arch. f. Mikr. Anat. XVI (1878), p. 203, t. xi, ff. 81, 32. Saccameba verrucosa Frunzrt Mikr. Fauna Argent. I, Prot. 1 (1892), p. 4, t. iv, ff. 1, 2, and 4 (1897), p. 146, in Bibl. Zool. IV. Body of the animal, when at rest, roughly spherical, oval, sub-quadrangular, or multilobate, always more or less rugose or verrucose. Forward movement effected by extensions of short anterior pseudopodia, or by broad wave-like expansions of the ectoplasm, which changes are accompanied by a wrinkling of the surface, resulting in the production of more or less regular longitudinal striations, very fine but distinctly AMGBA VERRUCOSA. 61 perceptible. Endoplasm granular, sub- -transparent, contaiing a spherical nucleus, and (in the posterior region) a contractile vacuole, which is usually con- spicuous, together with a variety of food-remains, animal or vegetable, or both. Habit very sluggish. Dimensions variable. Average length, during rapid march, about 2004. (Maximum 300-350 «, Greeff.) In the ooze of ponds, amongst submerged vegeta- tion, in tufts of moss growing on moist rocks, and in marshy places; widely distributed, but less common than A. proteus. The characters and habit of Ameba verrucosa separate it distinctly from every other member of the genus. The crinkled or striated ectoplasm is indicative of an unusual degree of surface-hardening, but cannot be regarded as evidence of a permanent envelope. The lines are often numerous and extremely delicate, extending longitudinally from the vicinity of the con- tractile vesicle forward to the anterior ectoplasm. They are most distinct at or near the margins where the protoplasm is least dense. The short, blunt, and generally very persistent wart-like protuberances on the surface of the body are a further distinctive feature. Pseudopodal movement is slow i in this animal. A. verrucosa 18 an omnivorous feeder. Besides desmids and other alge, individuals are sometimes found which contain the half-digested remains of infusorians and rotifers. (Pl. IV, fig. 1.) Some observers (e.g. Leidy in ‘ Freshw. Rhiz. N. Amer.’) have regarded what has since been described as A. striata Penard, as a young state of the species under notice—probably on insufficient grounds. The young of A. verrucosa, which we have sometimes met with, is normally a sub-spherical pellucid body (Pl. V, figs. la, 6, c), containing some granular, almost colourless endoplasm, and furnished with a nucleus and contractile vesicle. There is the wrinkled envelope of hyaline ectoplasm, extremely delicate, but clearly 62 BRITISH FRESHWATER RHIZOPODA. outlined. The figures show the successive phases presented by an individual, le exhibiting a distinct approach to the mature form of A. verrucosa by the production of one or two of the characteristic verrucose protuberances. The movements of the organism were extremely slow. A good deal of confusion has arisen regarding wl. verrucosa Hhrenb.,and A. terricola Greeff. Leidy, and more recently Penard, regarded the two as synonymous. Blochmann, whilst maintaining the specific claims of A, terricola, gives, in ‘ Die Mikros. Thierw. des Siiss- wassers,’ a figure which represents the resting-phase, as we have seen it, of A. verrucosa. These animals are subject to great variation. Carter, who first de- scribed the minute dA. quadrilineata, subsequently arrived at the conclusion that it was a young state of A. rerrucosa.* In this Leidy and others concurred. The latter author also, in the series of forms which he figured, included what Penard has since distinguished as A. striata. In A. verrucosa EKhrenb., Blochmann in- cludes A. quadvilineata Carter (80-100 »), and he main- tains A. terricola Greeff (350 yw) as a separate species. For the present, and until ambiguities have been removed, we consider it safer to make A. terricola synonymous with the original A. verrucosa of Ehrenberg. 10. Ameba pilosa Cash. (Plate IV, figs. 1-5.) Ameba pilosa Casu, in Journ. Linn. Soc., Zool. XXIX (1904), p. 219, t. xxvi, f. 8. Animal somewhat resembling an average-sized -lmeeba villosa, with the same pale-bluish or neutral- tinted, finely oranular protoplasm, and containing, as in that species, a variety of corpuscles, mostly chloro- phyllous, together with refringent yellowish or brownish oil-like globules. Nucleus pale; contractile vesicles * ©Ann. & Mag. Nat, Hist.,’ (2) xx (1857), p. 37. AMG@BA PILOSA. 63 one or more. The posterior extremity is produced into a delicately-fringed extension of faintly granular protoplasm, in which are usually to be seen one or two small vacuoles. Its external outline is irregular, with a tendency to become lobate. The entire body of the animal, including the posterior expansion, is covered with delicate spicules, radiating outwards, of equal length, and closely resembling those which invest the membranous test of Cochliopodium vestitum. This latter character at once distinguishes A. pilosa from all other known forms of Amaba. Locomotion is effected by lobular expansions of the ectoplasm, anterior or lateral. As in A. proteus and A. villosa the pseudo- podia may originate at any point of the body-surface. They have never been observed to become digitate. Dimensions: Length about 180 w; average breadth 50 p. In ponds at Chelford, Cheshire, amongst floating vegetation ; associated with Mastigaineba aspera Schulze, Ciliophrys infusionwm Cienk., etc.; June, 1908. In similar situations at Fearnhead, Lancashire. It is difficult to explain the origin and purpose of the delicate processes which so completely invest the body of this animal. Careful observation showed that upon the formation of a pseudopodal lobe, or broad eruptive expansion of the ectosarc, the spicules in- stantly flowed over it from the surrounding surface ; the continuity of the investment was thus ensured during all the animal’s movements. The Fearnhead examples of A. pilosa presented some differences from the typical Chelford form. They were probably older individuals. The investiture was the same, but it was observed that the individual spicules were stouter, and many of them were darker in colour, assuming often a yellowish-brown hue, whilst the endoplasm of the animal was denser. The posterior expansion was entirely wanting, and the animal was much less active. 64 BRITISH FRESHWATER RHIZOPODA. Genus 2. DACTYLOSPHARIUM Hertwig & Lesser, 1874. Amba (pars) Enxrensere in Abh. K. Akad. Wiss. Berlin, 1830 (1832), p. 39, and Infus. (1838), p. 128. Dactylospherium Hertwie & Lesser in Arch. f. Mikr. Anat. X (1874), Suppl., p. 54. Body ameeboid; distinguished from Ameba by the possession, during the quiescent phase, of rigid or but slightly flexuose pseudopodia, which radiate irregularly from the sub-globular body-mass, and are variable in number and length. Pseudopodal movements slow, the pseudopodia often immobile for long periods ; endoplasm as in Ameba, generally colourless or only slightly tinged with green, except in D. polypodium. The latter, in the density and colour of its endoplasm, approaches J/astigameba. The rigid and frequently elongated and pointed pseudopodia (in the resting-phase) mainly characterize this genus. D. vadiosum is truly amoeboid in the active phase. 1. Dactylospherium radiosum (Ehrenb.) Biitschli. (Plate IIT, figs. 8-11; Pl. IV. figs. 6-11.) Ameba vradiosa Hurensure in Abh. K, Akad. Wiss. Berlin, 1830 (1832), p. 39; op. cit. 1831 (1832), p. 80; and Infus. (1838), p. 128, t. viii, f. xiii; Prircnarp, Nat. Hist. Ani- male. (1834), p. 38; Hist. Infus. (1842), p. 166, t. ii, f. 88; new ed. (1852), p. 202, t. 1i, f. 88; and ed. 4 (1861), p. 549, t. xxil, ff. 1-3; Perry Kenntn. kleinst. Lebensf. (1852), p- 188; Cotmin Proc. Essex Inst. I (1853), p. 45; Scumarpa Grundz. Zool. I (1853), p. 26, f. 15; Averpacn in Zeits. f. wiss. Zool. VIT (1856), p. 400, t. xxi; Piex in Verh. Vereins Wien, VII (1857), p.36; Carrenrmr Foram. (1862, Ray Soc.), p. 24, t.1, £. 15; t. iv, ff. 6,7; Carus Handb. Zool. IT ae p. 591; Wauiich in Ann. Nat. Hist. (3) XI (1863), 443; Winuramson in Pop. Sci. Rev. \ (1866), p. 197, t. xiii, ff. 14-16; Czmrny in Arch. f. DACTYLOSPHERIUM RADIOSUM. 65 mikr. Anat. V (1869), p. 161; Rotieston Forms Anim. Life (1870), p. 257, t. xii, f.9; Greene Man. Prot. (1871), p. 4, f.1; Mager in Atti Soc. Ital. XIX (1876), p. 407, and in Rend. R. Ist. Lomb. (2) XXI (1888), p. 308; Guza in Herausg. Ungar. Nat.-Mus. Budapest, I (1877), p. 166; Carrango in Atti Soc. Ital. XXTI (1878), p. 31, and in Boll. Scient. I, an. 1 (1879), p.7; Lumpy Freshw. Rhiz. N. Amer. (1879), p. 58, t. iv, ff. 1-18, and in Proc. Acad. Nat. Sci. Phil. (1879), p. 163; Leucxarr in Boll. Scient. I, an. 1 (1879), p. 14; Futtagar in Sci. Goss. 1880, p. 204, f. 127; Merescuxowsky in Arch. f. mikr. Anat. XVI (1880), p. 200, t. xi, ff. 383-85; Parona in Boll. Scient. I, an. 2 (1880), p. 24, and 1. c. an. 4 (1882), pp. 51, 56; Hircacock Synops. Freshw. Rhiz. (1881), p.5; Nrcnorson Classif. Anim. Kingd. (1882), p. 5, f. 38, and Man. Zool. ed. 7 (1887), p. 76, f. 178; Botron in Midl. Nat. IX (1886), p. 174; Wuuiretuces in Proc. Linn. Soc. N. 8. Wales, (2) I (1886), p. 449; Fretpz in Proc. Acad. Nat. Sci. Phil. 1887, p. 122; Harvey in Amer. Nat. XXII (1888), p. 72; Metssner in Zeits. f. wiss. Zool. XLVI (1888), p. 505; Saccm1 in Boll. Scient, IIT, an. 10 (1888),-p. 42, and J. c. an. 11 (1889), p. 67: Cerrzs Cap. Horn Zool. VI (1889), Prot. p. 20; Mesicvs in Abh. K. Akad. Wiss. Berlin, 1888 (1889), 2, p. 25, t. v, ff. 52-54; Cuneo in Boll. Scient. ITI, an. 12 (1890), p. 142; Prnarp in Mém. Soc. Phys. Genéve, XXXIJ, no. 2 (1890), p. 131, t. i, ff. 73-76; t. ili, f.i1; in Rev. Suisse Zool. IX (1901), p. 237; and Faune Rhiz. Léman (1902), p. 86, ff.; Pzrry in Proc. Amer. Soc. Micr. XIT (1891), p. 94; Casz in Trans. Manch. Micr. Soc. 1891 (1892), p. 48, #. u1, f. 28; Lorp in Trans. Manch. Mier. Soc. 1891 (1892), p- 56; Jenurre in Amer. M. Micr. Journ. XIV (1893), _p. 289; Loner in Atti Soc. Ligust. V (1894), p. 16; ScouRFIELD in Proc. Zool. Soc. 1897, p. 787; RuumBiEr in Arch. f. Entwick. VII. (1898), pp. 144, 198, f. 16; Monrt in Rend. R. Ist. Lomb. (2) XXXII (1899), p. 161 ; Catgetns Prot. (1901), p. 80; Issen in Atti Acc. Torino, XXXVI (1901), pp. 68, 70. Amiba radiosa Dusarpin in Ann. Sci. Nat. TV (1836), p. 237, and Infus. (1841), p. 286, t. iv, ff. 2, 3; Scuocu Mikr. Thiere Siisswass. I (1868), p. 10, t.1, f. 17; Berconzin. in Atti Soc. Nat. Modena, Rend. I (1882), p. 22. Amiba brachiata Dusarpvin Infus. (1841), p. 238, t. iv, f. 4. Ameba brachiata Fromunte, Etudes Microz. (1874), p. 347, t. xxix, f.4; Carranzo in Boll. Scient. I, an. 3 (1882), 5) 66 BRITISH FRESHWATER RHIZOPODA. 116, and op. cit. III, an. 10 (1888), p. 91; Saccuz in Boll. Scient. III, an. 10 (1888), p. 41. Ameba radiosa Maaar i in Rend. R. Ist. Lomb. (2) IX (1876), p. 511, and in Boll. Scient. I, an. 2 (1880), p. 35. Astrameba radiosa VEIDOvSKY ‘in Sitz-ber. K. Bohm. Ges. Wiss. 1880 (1881), p. 188, and Thier. Org. Brunn. Prag (1882), p. 36, t. i, f. 6. _Dactylospheria radiosum Birscaui in Bronn’s Thier-Reichs, 1 (1880), t. i, £. 10. Dactylospheria radiosa Lanussan Traité Zool., Prot. (1882), p. 47, f. 34; Berconzinr in Atti Soc. Nat. Modena, Memor. (3) IT (1883), p. 73. Dactylospherium radioswm Burocamann Mikr. Thierw. Siiss- wass. (1886), p. 11, t. i, f. 10, and ed. 2 (1895), p. 14, t. 1, f.6; Frenze, Mikr. Fauna Argent. I, Prot. 1 (1892), p. 32, t.i, f. 5, and 4 (1897), p. 148, in Bibl. Zool. IV; Detace & Hirovarp Zool. concer. I (1896), p. 99, f. 106; TFrancé Result. Erfors. Balatons. II, 1 (1897), p. 6; Levawnper in Acta Soc. Fauna Fenn. XX (1901), no. 6, p. 5; G. 8. West in Journ. Linn. Soc., Zool. XXVIII (1901), p. 310, t. xxviii, ff. 4,5; op. cit. XXTX (1903), pp. 109, 118, t. xiii, ff. 1, 2; andin Amn. Scott. Nat. Hist. 1905, p. 81. Animal small and generally inactive, globular or oval in outline, and exhibiting three or more—in some individuals as many as six or eight—pseudopodia, which frequently take the form of immobile arm-like projections varying in length and degree of rigidity. They may be short and stumpy, tapering from a broad base, or elongated to several times the diameter of the body, of nearly equal width throughout and blunt at the apex, or long, straight, and tapering acutely. As a rule they radiate from all parts of the body-surfacé, and remain for long periods without perceptible change. In this condition the animal is quite passive, floating in the water or driven about by currents. The body consists of granular protoplasm, and when all the pseudopodia are withdrawn it may become sub- spherical or bluntly lobed ; or it may assume an active amoeboid phase, when it 1s hardly, if at all, distinguish- able from the smaller forms of slmaba. proteus. Chloro- phyllous food is taken during the periods of activity. DACTYLOSPHERIUM RADIOSUM. 67 Dimensions variable : diameter of body usually about 30; length of pseudopodia sometimes 120 », or over. In marshes and pools, amongst submerged vegeta- tion, and in moss on dripping rocks ; less common than Ameba proteus, with which it is often associated. The rayed disposition of the pseudopodia and their rigid habit are characteristic of this species. Fre- quently the arms are curved, bent at an angle, or waved. A pseudopodium in extending or retracting will sometimes assume a spiral form and remain rigid in that attitude indefinitely. The endoplasm, as a rule, is uniformly granular, and the chlorophyllous matter occupying it is sparser than in the common Amebe. Biitschli transferred this form to the genus Dactylo- spheriun. (which he named in error Dactylospheria), though it must be confessed that there are few points of affinity between it and D. polypodinm, so that there is some ground for Vejdovsky’s view that it should form the type of a new genus which he named Astrameba. Penard, however (‘ Faune Rhiz. du Bass du Léman’), does not consider that either Dactylosphe- rium radiosum or D. polypodiuim should be separated from the true Am@be. 2. Dactylospherium polypodium (Max Sch.) Biitschli. (Plate III, fig. 12; Pl. IV, fig. 12.) Ameba polypodia Max Scuvttze Organism. Polythal. (1854), t. vill, f. 21; F. E. Scaurze in Arch. f. mikr. Anat. XI (1875), p. 592, t. xxxvi; AtLMan in Journ. Linn. Soc., Zool. XIII (1877), p. 276; Cravs Lehrb. Zool. (1885), ff. 11, 184, and (Engl. transl.) Text-book Zool. I (1884), p. 22, ff. 11, 121; Grouper in Zeits. f. wiss. Zool. XI (1884), p. 128; Mager in Rend. R. Ist. Lomb. (2) XXT (1888), p. 306; Herrwie Lehrb. Zool. I (1891), p. 149, f. 116; ed. 2 (1900), p. 160, f. 114; and (Eng. transl.) Man. Zool. (1903), p. 189, f. 119; Sepewicx Text-book Zool. I (1898), p. 4, £. 2; Jorpan & Kuttoe Anim. Life (1900), p. 8, f. 4; Cazxins Prot. (1901), p. 80. 68 BRITISH FRESHWATER RHIZOPODA. Dactylospherium vitrewm Herrwie & Lesser in Arch. f. mikr, Anat. X (1874), Suppl. p. 54, t. ii, f£. La (non 13) ; ALLMAN in Journ. Linn. Soc., Zool. XII (1877), p. 266, f.1; Arcuer in Q. J. Micr. Sci. XVII, n.s. (1877), p. 344, t. xxi, f. 17; Parona in Boll. Scient. I, an. 6 (1884), p. 56; Biocumann Mikr. Thierw. Siisswass. (1886), p. 11, t.1, f. 10, and ed. 2 (1895), p. 14, t.1,f.7; G.S. Waser in Journ. Linn. Soc., Zool. XXVIII (1901), p. 310. Dactylospheria polypodia Btrscuit in Bronn’s Thier- Reichs, I, 1 (1880), t.i, f. 11. Dactylospherium polypodiwm Lanessan Traité Zool., Prot. (1882), p. 48, f. 35. Dactylosphera polypodia Ray Lanxzster in Encycl. Brit. ed. 9, XIX (1885), p. 842, f. iv, 1-38; Loner in Atti Soc. Ligust. (1894), p. 16; Detace & Hérovarp Zool. coner. I (1896), p. 99, £. 107. Ameba vitrea Penarp Faune Rhiz. Léman (1902), p. 84, ff. According to the description given by Hertwig and Lesser this species has a spherical or sub-spherical body, from which radiate blunt or conical pseudopodia, in length usually about half the diameter of the body, and, like the border, consisting of a “ perfectly homo- geneous, quite clear, glassy-looking plasma.” Immersed in the protoplasm are a great number of greenish, strongly-refractive granules, varying in size. Two forms of the organism are described, one being green, the other a bright clear yellow. The coloured elements are crowded, filling the body-mass all but the narrow hyaline border, and preventing any view of the nucleus. In most, if not all, of the examples of the green form met with by Hertwig and Lesser, the entire superficies, including the pseudopodia, was covered by “peculiar protoplasmic hair-like prolongations, in which, however, no movement was_ perceptible.” Amongst other points of distinction Hertwig and Lesser say that the green examples lay motionless and at rest, appearing as more or less regular balls, and only these, with them numerous pro jected pseudopodia, showed a slow forward or backward movement. With the yellow-coloured individuals the case was different. These not only moved with comparative rapidity, aided DACTYLOSPHARIUM POLYPODIUM. 69 by their quickly-projected, mostly numerous pseudo- podia, but even their body-mass took an active share in locomotion, similar to that of Amube. Dimensions: Diameter of body (without pseudo- podia) 6-12 p. Various localities in Cheshire. Shelf, West York- shire (G. S. West). Chipperfield, Herts (A. Harland). The genus Dactylospheriwm was established by Hertwig and Lesser to receive the organism named by them Dactylospheriwm vitreum. One form of this appeared to be closely allied to, if not identical with, forms of Mastigameba aspera F. E: Schulze. Mr, John Hopkinson has been at considerable pains recently to investigate the relationships of the different forms described by these authors, and has come to the con- clusion that the species which we here refer to Dactylospherium polypodium, is the same organism as Ameba polypadia Max Sch. and F. HE. Sch., and also Dactylospherium vitreum Hertw. & Less., t. ni, f. 1a (the yellow form), whilst Dactylospherium vitreum Hertw. & Less., t. 11, f. 1B (the green form) referred to in the preceding pages, although much like some forms of Mastigameba aspera, is a distinct species to which the name D. vitreum should be restricted. Lanessan, in ‘ Traité de Zool., Protozoaires’ (1882), distinguishes between Dactylospherium polypodium Max Sch. sp, and D. vitrewm Hertw. & Less., indicating characters for the latter which are strictly those of Hertwig and Lesser’s f. 18, and likewise consistent with what we have observed in Mastigamcaba aspera. Genus 3. MASTIGAMGBA F. E. Schulze, 1875. Mastigameba F. BE. Scxunze in Arch. f. mikr. Anat. XI (1875), p. 583. Animal amoeboid in structure and habit; during progression elongated, elliptic or ovoid; the body 70 BRITISH FRESHWATER RHIZOPODA. narrowed anteriorly, and forming a conical lobe or prominence from which emanates a long and active flagellum. Pseudopodia short, radiating {qutwards from the cortical ectoplasm, simple or ramulose. The body-surface, in at least one species, is habitually covered with minute bacilliform spiculee. 1. Mastigameba aspera IF. E. Schulze. (Plate VI, figs. 1-5.) Mastigameba aspera F. K. Scuurze in Archiv. f. mikr, Anat. XI (1875), p. 583, t. xxxv; AtLMan in Journ. Linn. Soc., Zool. XIII (1877), p. 268, f. 8; Arcugr in Q. J. Micr. Sci. XVII, ns. (1877), p. 350, t. xxi, f. 24; Kuwr Man. Infus. I, pt. 2 (1880), p. 221, t. i, f. 21; Lanzssan Traité Zool., Prot. (1882), p. 50, f. 88; BirscHrr in Bronn’s Thier-Reichs, I, 2 (1888), t. xxxix, f. 9; Grirriras & Henrrey Micr. Dict. ed. 4 (1883), p. 492, t. liii, f. 22; Hertrwie Lehrb. Zool. I (1891), p. 147, f. 43; ed. 2 (1900), p. 159, f. 118; and (Engl. transl.) Man. Zool. (1908), p. 188, f. 118; Catxins Prot. (1901), p. 103, f. 57a, Animal, in the resting phase, sub-spherical or oval, ultimately, when in active movement, becoming elon- gated and narrowed anteriorly, whilst the posterior ex- tremity remains rounded, or, in what may be younger individuals, is produced into arounded lobe. The body is susceptible of considerable modifications, changing from globular to oval, or becoming bluntly angular, whilst throwing out numerous amoeboid pseudopodia, in which condition the organism is hardly distinguish- able from some forms of Amba, except by its highly- refringent and denser protoplasm. In the mobile state (Pl. VI, fig. 1) the pseudopodia are numerous, variable in length, usually simple and straight, rarely bigeminate or forked, mostly attenuated but blunt at the apex, and never becoming filamentous or acicular. The posterior ones are short; those immediately in front, on either side of the frantal lobe, longer and MASTIGAM@BA ASPBRA. “1 narrower, and generally pellucid. The arrangement of the pseudopodia, in this aspect of the animal, is fairly regular: they extend outwards from the margins of the compressed body, being, in fact, extensions of the ectoplasm, and appear to occupy a common plane. The refringent character of the ectoplasm extends also to the pseudopodia, and is heightened by the presence of innumerable minute spicule which adhere to the surface tangentially or horizontally. The nucleus is single, imbedded in the anterior ectoplasm just behind the frontal lobe, and is sometimes hidden by the semi- Opaque granular endoplasm. From this lobe the flagellum extends outwards, its point reaching beyond the extremities of the pseudopods; it is hyaline, very refractive, and always alert, moving and coiling with great rapidity ; from which circumstance it is not in- frequently difficult of detection. Contractile vesicles, usually two, on opposite sides of the body, in the posterior region. Dimensions variable: length averaging 150-200 p; average breadth about 50 p. In the ooze of ponds, and amongst floating vegeta- tion, at Chelford and Northenden, Cheshire; and at Fearnhead, Lancashire. The facial aspect of Mastigamaba aspera differs remarkably from that of the larger dinwbe with which it might be confounded. It attracts attention at once by its refringent protoplasm. The flagellum, its pecu- liarly-distinctive feature, is stated by F. E. Schulze to be 0:06-0:08 mm. long, and is rightly described by him as “a very fine filament of equable but hardly- defineable character, and considerable refractive power.” It is not attenuated at the extremity but of equal thickness throughout, and ends “as if abruptly cut off.” The movements of the animal are distinctly amceboid ; the action of the flagellum has no effect as an organ of locomotion, though in very young and small indi- viduals its rapid movements do seem at times to 72 BRITISH FRESHWATER RHIZOPODA. produce a slight jerky motion of the body from side to side. The nucleus is prominently situated, appearing in some individuals as an irregularly-rounded body, strongly refractive, and about 9 w in diameter. Schulze remarks that it is surrounded by a clear space, and that within its substance may be detected “a number of minute globular, sharply-bounded clear spots, which have the power of altering their positions.” Usually two contractile vacuoles may be observed imbedded in the densely-granular protoplasm near the periphery, on each side. Their pulsations appear to be very languid. The bacilliform spicules, of which mention has been made, line the outer surface of the body in a thin stratum, apparently imbedded in a mucous film. They vary in number; in some individuals so few as to be hardly perceptible ; in others thick enough to justify the specific name given to the organism. In water from a pond at Northen Etchells, Cheshire, about the end of June, a form of Mastigamalba occurred which presented a remarkable variation from the type. The posterior extremity, instead of being broadly rounded, formed a circular expansion of ectoplasm, finely granular, containing some small vacuoles, and fringed with short radiating conical or acute pseudo- podia, of very delicate structure. A few minute spicules could be detected on the surface of this appendage, but neither on the body nor on the pseudo- podia proper were any visible. The pseudopodia, in these abnormal examples, were more attenuated and fewer in number than in the others, and at the same time more pellucid. The flagellum was active in most cases, seeming to perform the function of a tentacle. The individuals were comparatively small, and generally lighter m colour, and they had a wider margin of ectoplasm. For the present we retain this (PI. VL f. +) as a variety—M. aspera, var. cestricnsis. MASTIGAM@BA RAMULOSA. 73 ' 2. Mastigameba ramulosa Kent. (Plate VI, fig. 6.) Mastigameba ramuloss Kent Man. Infus. I, pt. 2 (1880), p. 222, t. 1, ff. 19, 20. Body during active movement elongate-ovate, about one and a half times longer than broad, the entire peripheral surface bearing sub-equal branched pseudo- podal prolongations. Neither these nor the general surface of the body show secondary hispid pseudo- podia. The flagellum exceeds the body in length. The nucleus is sub-central and spherical; the con- tractile vesicle is located posteriorly. Dimensions: Length (according to Saville Kent) 1-400" (63 ). In marsh-water, as yet only met with in Jersey (Kent). The description of this organism is from Kent’s ‘Manual of the Infusoria.’ The author says that the conspicuously - branched character of the abundant pseudopodia serves to distinguish it readily from other forms, and communicates to it, as a whole, an aspect suggestive of a minute Nudibranch. Under any dis- turbing influence the little animal immediately con- tracts ito a sub-spheroidal contour. It was observed that the granule-circulation, conspicuously indicated in the centre substance of the body, did not extend into the branched pseudopodia, nor were these appendages withdrawn entirely within the periphery at any time. Genus 4. PELOMYXA Greeff, 1874. Pelobius* Greerr in Verh. nat. Ver. Rheinl. XX VII (1870), pp. 198, 200. Pelomywa Greurr in Arch. f. mikr. Anat. X (1874), p. 51. Ameeboid rhizopods mostly of large size with a hyaline ectoplasm and granular semi-fluid endoplasm, * Pre-occupied in Coleoptera. 74 BRITISH FRESHWATER RHIZOPODA. the latter usually containing large quantities of ex- traneous matter and miscellaneous food particles, and always numerous clear corpuscles (the glanzkdérper of German naturalists) regarded by the earlier observers as zoospores, but more recently proved to be albuminoid, and probably a source of nourishment to the symbiotic bacteria with which the body of the organism is charged.* Nuclei in some species very numerous and minute ; in others of the ordinary type, and fewer ; contractile vacuole absent, its place being apparently taken by numerous small watery-looking vacuoles dis- persed through the endoplasm. Locomotion effected by broad lobular or wave-like expansions of the frontal ectoplasm, or by pseudopodia originating on any part of the surface, the posterior extremity during active movement appearing rounded, and being furnished with short sub-persistent hyaline pseudopodia, or with a spherical lobe of granular structure (less dense than the substance of the body), the surface of which is covered with villous processes. 1. Pelomyxa palustris Gruerr. (Plate VII, figs. 1-3.) Pelomyea palustris Greerr in Arch. f. mikr. Anat. X (1874), p. 51, tt. ii-v; F. E. Scrutze in Arch. f. mikr. Anat. XI (1875), p. 342, t. xix, ff. 6-8; Gasrren in Morph. Jahrb. I (1876), p. 541; Atrman in Journ. Linn. Soc., Zool. ATI (1877), p. 271, f. 5; Arcuer in Q. J. Mier. Sei- XVIT, ns. (1877), p. 337, t. xxi, ff. 10-15+; EneGeLmann in Arch. ges. Physiol. XIX (1879), p. 1; Bivscu1i in Bronn’s Thier-Reichs, I, 1 (1880), t. ti, f. 1; Mikros. Schaume (1892), p. 216; and (Engl. transl.) Micros. Foams (189-4), p- 116; Kororyurr in Arch. Zool. expér. VIII (1880), p. 476, t. xxxvi, ff. 6-23 ; Lapnam in Amer. Journ. Micr. V (1880), pp. 165, 197 ; Lanrssan Traité Zool., Prot. (1882), p. 44, ff. 82, 83; Ray Lanxesrer in Encycl. Brit. ed. 9, XIX (1885), p. 842, f. iv, 5,6; Berruonp Stud. Protopl.- mech, (1886), p. 109, t. ii, f. 6; Brochmann Mikr. Thierw. * Mrs. L. J. Veley, in ‘ Journ. Linnean Soc.,’ Zool., vol. xxix, pp. 875-386. + As P. lacustris in Zool. Ree. for 1877, Prot. p. 4. PELOMYXA PALUSTRIS. 75 Siisswass. (1886), p. 10, t.i,f. 9; ed. 2 (1895), p. 18, t. i, f. 5; and in Biol. Centralbl. XIV (1894), pp. 86, 115; Wartetxags in Proc. Linn. Soc. N. 8. Wales, (2) I (1886), p. 499; Guriiver in Journ. R. Micr. Soc. 1888, p. 11 ; Maissner in Zeits. f. wiss. Zool. XLVI (1888), p. 505; Verworn Psychophys. Prot. Stud. (1889), pp. 40, 161, etc., t. iv, f. 18; Bourne in Quart. Journ. Micr. Sci. XXXII, n.s. (1891), p. 362, etc., Hertwieg Lehrb. Zool. I (1891), p. 149; ed. 2 (1900), p. 160; and (Hngl. transl.) Man. Zool. (1903), p. 189; Voeltzkow in Zool. Anzeig. XIV (1891), p. 228; Pzyarp in Arch. Sci. Phys. XXIX (1893), p. 165; in Rev. Suisse Zool. VII, 1 (1899), p. 18; op. cit. VIII (1900), p. 486; op. cit. IX (1901), p. 238; and Faune Rhiz. Léman (1902), p. 189, ff.; Surptey Zool. Invert. (1893), p. 10, £.3; Gounp in Q. J. Micr. Sci. XXXVI, ns. (1894), p. 295, tt. xx, xxi; Levanper in Acta Soc. Fauna Fenn. (1895), no. 2, p. 12; De.ace & Hérovarp Zool. concr. I (1896), p. 100, £. 112 ; Prowazex in Biol. Centralbl. XVII (1897), p. 881; Ruvmsier in Arch. f. Entwick. VII (1898), p. 118, f. 2, t. vi, f. B; Mont in Rend. R. Ist. Lomb. XXXII (1899), p. 161; Srote in Zeits. f. wiss. Zool. LXVIII (1900), p. 625 ; Wiigow in Amer. Nat. XXXIV (1900), p. 548, ete. ; Catxins Prot. (1901), p. 95; G.S. Wzsr in Journ. Linn. Soc., Zool. XXVIII (1901), p. 309, and op. cit. XXIX (1903), pp. 109, 112; CasH in Journ. Linn. Soc., Zool. XXIX (1904), p. 218; Vetey in Journ. Linn. Soc., Zool. XXIX (1905), p. 374, tt. xxxvi-xxxvili, f. on p. 391. ? Ameba princeps Czzrny in Arch. f. mikr. Anat. V (1869), p. 159.* ? Ameeba proteus Braytuy in Sci. Goss. 1886, p. 19.* Body of large size, presenting during active move- ment a rounded, oval, or elongated figure, often broadly lobed and irregular. Adult individuals opaque, from the presence in the colourless endoplasm of an extra- ordinary quantity of incepted matter, consisting of mud, sand-particles, and decayed vegetable débris ; bounded externally by a thin layer of finely-granular or hyaline ectoplasm. With the other contents, there may often be observed various organisms which have been taken as food (enclosed in large vacuoles) * Described as abnormally large forms of the species to which they were referred. 76 BRITISH FRESHWATER RHIZOPODA. including desmids and other alge, and sometimes also rotifers and entomostraca. Such a mass of foreign matter renders a study of the physiological structure of this organism difficult in adult individuals; but in younger examples, sometimes though rarely met with, the body-substance being transparent, the “shining bodies,” of rounded or oval figure, can readily be seen, imbedded in the hyaline and homogeneous protoplasm, besides numerous vesi- cular spaces, lying, as described by Greeff, in the richly-granular intervening substance, the whole not unlike Actinophrys Hichhoruvi, but not so regular or compact. The vesicles vary in size, and their place in the protoplasmic substance is subject to constant change, such change being governed by the move- ments of the organism. In addition to the elements described, there are always present, in this species, rod-like bacteria scattered through the protoplasm in great numbers. Greeff remarks that the body, in Pelomyxa palustris, consists of pure protoplasm, and is composed of two strata—an outer cortical one and an inner parenchyme. The former is hyaline and homogeneous; it is the chief seat of contractility, and hence in it the loco- motive power resides. The whole inner parenchyme is of thinner consistence and is but passively moved ; itis richly granular and filled with watery vacuoles, often so crowded that the substance appears reticu- lately interrupted. The two strata are not sharply marked off, but pass gradually into one another. In the so-composed body-mass there occur, then, three structures—(1) nuclei; (2) hyaline and homogeneous bodies of roundish, ovoid, or irregular figure, and glossy appearance (the glanzhs pen) § and (3) fine bacilliform bodies. These have for some time been regarded b most authors as symbiotic bacteria, and that this is their true nature has now been proved. P. palustris is multi-nucleated. The nuclei are small and obscure; irregularly distributed between PELOMYXA PALUSTRIS. 77 the vacuoles of the endoplasm, most numerously in the central region ; sparingly elsewhere (Pl. VII, figs. 1-3). In examples, say 1 mm. in diameter, there may, Greeff says, be some hundreds. This author describes them as delicately-walled bodies of globular, more rarely oval, figure, averaging 0°012 mm. in diameter. Their hyaline contents are pervaded more or less by dark granules; and their position, form, and appearance give in all respects the indubitable impression of cell- nuclei. Reproduction takes place by fission, or, as has been more generally observed, by the formation of amoeboid zoospores. The amcebule, after liberation, pass into a resting state, and ultimately develop a flagellum, or vibratile filament, passing thence into the adult phase. Dimensions variable, mature individuals attaining 2 mm. diameter (Greeff) ; average diameter of a quies- cent individual, exclusive of the pseudopodia, about 150 p. In the ooze of ponds and ditches, especially such as are partially shaded, in bogs, and amongst Sphagnum in stagnant water; not very frequent. This organism is the largest of the amoeboid rhizo- pods. To the naked eye it is often visible as a speck of semi-opaque matter—yellowish brown by trans- mitted light—of which the outline undergoes constant change. Fies. 22 anp 23.—Arcella dentata (side views): 22,a Swiss form, after Penard; 23, an American form, after Leidy. x 250. 5. Arcella artocrea Leidy. (Figs. 24 and 25.) Arcella artocrea Lerpy in Proc. Acad. Nat. Sci. Phil. 1876, p. 57; Freshw. Rhiz. N. Amer. (1879), p. 178, t. xxx, ff. 1-9; Corrapo in Boll. Scient. J, an. g (1880), p AT; Rouuzston Forms Anim. Life, ed. 2 (1888), ee 901; ScourFigetp in Proc. Zool. Soc. 1897, p. 788; G. S. Wzst in Journ. Linn. Soc., Zool. XXVIII (1901), p. 315, t. xxvii, f. 2; ? Penarp Faune Rhiz. Léman (1902), p. 404, ff., and p. 665. Test in height from one fourth to less than half the breadth ; the dome convex and even, or mamillated, or pitted ; basal border everted and rising from a quarter to nearly half the height of the test, obtusely 128 BRITISH FRESHWATER RHIZOPODA. angular, and entire, the central portion of the base everted in the usual concavely infundibuliform manner; the mouth circular, entire, surrounded with a circle of minute tubercles. The plasma-body having the same general form and relationships as in other Arcelle, but rendered bright green from the presence of abundance of chlorophyl-corpuscles in the endo- plasm. Pseudopodia colourless, digitate. Fia. 24, Fic. 25, Fias. 24 and 25.—Arcella artocrea (face and side views), after Leidy. x 250. : Dimensions : Greatest breadth, 176 pw (Leidy). Bog above the lakes at Capel Curig, North Wales; Co. Donegal, Ireland (G. 8. West). The species seems to be very rare, even in America. West (loc. cit.) found, in the locality above mentioned, a very large form, the diameter of the test (inclusive of the rim) measuring 300 4; that of the mouth 32 p; the height of the test beng about 110. Specimens from County Donegal, Ireland, were not more than 85 win diameter, Only empty tests were observed. ‘he body of these was faceted, as in many of the more angular forms of A. valgaris. PSEUDOCHLAMYS. 129 Genus 16. PSEUDOCHLAMYS Claparéde & Lach- mann, 1859. Pseudochlamys Ciararinn & Lacumann Etudes Inf. et Rhiz. 2 (1859), p. 448. Amphizonella Gruery in Arch. f. mikr. Anat. II (1866), p. 323. Test discoid, flexible when young, protecting the plasma-body, which contains a central nucleus and several contractile vesicles. This genus was established by Claparéde and Lach- mann. (loc. cit.) to include a minute and highly-curious Arcella-like organism. Ordinarily the test is smooth, and, in the young state, quite transparent, but it becomes brown with age, most deeply coloured in the centre, and shading off towards the margin, sometimes appearing ‘‘faceted or punctate” according to these authors. Hertwig¢ and Lesser (‘ Arch. fiir mikr. Anat.,’ 1874) represent the concavity of the test, which in general shape resembles a watch-glass, as being closed, all but a central opening, by a delicate and hyaline continuation of the rim, completing the external resemblance to Avcella. Penard figures the same (‘Faune Rhiz. du Bassin du Léman,’ p. 181). The peripheral membrane is so exceedingly attenuated that the structure referred to is very difficult to make out. In the scores of empty tests we have examined, only in one instance did we find the faintest semblance of a central opening. 1. Pseudochlamys patella Claparéde & Lachmann. (Plate XVI, figs. 1-9.) Pseudochlamys patella CLaparnpe & Lacumann Etudes Inf. et Rhiz. 2 (1859), p. 443, t. xxu, f. 5; CarpEnrer Foram. (1862, Ray Soc.), p. 25; Herrwic & Lesser in Arch. f. mikr. Anat. X (1874), Suppl. p. 100, t. iii, f. 1; F. E. Scuurze in Arch. f. mikr. Anat. XI (1875), p. 332, t. xviii, ff. 7-14; Atrman in Journ. Linn. Soc., Zool. XIII (1877), p. 393, f. 3; ArcHuR in Q. J. Mier. Sci. XVII, 9 130 BRITISH FRESHWATER RHIZOPODA. ns. (1877), p. 107, t. viii, ff. 1-3; Buck in Zeits. f. wiss. Zool. XXX (1878), pp. 5,12; Maaar in Atti Soc. Ital. XXI_ (1878), pp. 314, 319, and in Boll. Scient. I, an. 2 (1880), p. 35; Birscutt in Bronn’s Thier-Reichs, I, 1 (1880), t.1i, #.8; Lanessan Traité Zool., Prot. (1882), p. 51, f. 389; Parona in Boll. Scient. I, an. 4 (1882), pp. 52, 56; Brocumann Mikr. Thierw. Siisswass. (1886), p. 12, t. 1, f. 15, and ed. 2 (1895), p. 15, t. i, f. 11; Carranzo in Boll. Scient. IIT, an. 10 (1888), p. 91; Saccur in Boll. Scient. III, an. 10 (1888), p. 44; Lower in Atti Soc. Ligust. V (1894), p. 17; Detace & Hirovarp Zool. concr. I (1896), f. 122; Catxins Prot. (1901), f.13c; Pryarp in Rey. Suisse Zool. IX (1901), p. 238, and Faune Rhiz. Léman (1902), p. 180, ff., and p. 666; CasH in Journ. Linn. Soc., Zool. XXTX (1904), p. 218. Amphizonella flava Greurr in Arch. f. mikr. Anat. II (1866), p. 329, t. xviii, f. 19; Creventt and Mager in Rend. R. Ist. Lomb. (2) III, p. 369; Tripp in Proc. Bristol Nat. Soc. n.s. IV (1870), p. 19; Macar in Atti. Soc. Ital. XXI (1878), p. 314. Test discoid, generally circular, concave, in the young state hyaline and flexible, becoming rigid and brown with age; sometimes, in the latter condition, punctated on the convex surface, or, according to Archer, presenting an appearance of faceting or shagreening, “due to little rounded, closely-posted, scattered scrobiculi.” The flexibility of the test, when young, is shown by its assuming a variety of forms, being at one moment discoid, at another folded in upon itself, wholly or partially, or rolled together scroll-lke. A short finger-like pseudopod is sometimes protruded from between the folds. Nucleus central; contractile vesicles several, peripheral. Dimensions : Diameter of test 40-45 p. Amongst submerged vegetation (e.g. Hypnum fluitans) in ponds, and amongst Sphagnwn. In Cheshire ponds abundant, chiefly in the spring months, associated with Microgromia socialis. The variations of figure of the test of Psendochlumys, when young, correspond with the activities of the animal. There is a close attachment of the plasma- PSEUDOCHLAMYS PATELLA. 1381 body to the interior of the test, the latter appearing to be fully occupied, when the discoid figure is examined, except a narrow hyaline margin. Usually the animal begins an active movement by raising the margin of the test on the opposite side; the movement will be continued until the opposite margins approach and the figure becomes roughly-speaking semi-circular ; or the margins will overlap, and the animal will remain thus curiously rolled together for some time, its general form being comparable to that of the chrysalis of a lepidopterous insect. The discoid form admits of the endoplasm being readily studied. Four or more contractile vacuoles may usually be seen, pulsating languidly, on the outer margin of the plasma-body ; and a central nucleus is also visible, though not conspicuous. The brown colour of the test and its rigidity are dis- tinctive of old individuals. Empty tests may at an time be met with where the species is abundant; they are seen to vary little, if at all, in size or structure. They differ widely in appearance from the tests of the Arcelle, being very much smaller, simple, and concave, usually of a deep brown, and sometimes punctated about the centre, the colour gradually shading off towards the margin, which is rarely found inverted. Although undoubtedly distinct, the affinities of Pseudochlamys are with Arcella. We have found the organism most abundant in spring, amongst floating Hypna in ponds. Later in the year it seems to disappear. Genus 17. CENTROPYXIS Stein, 1859. Arcella (pars) Enrenperc in Abh. K. Akad. Wiss. Berlin, 1830 (1832), p. 40. Arcellina Canton in Ann. Nat. Hist. (1) IX (1842), p. 362. Difflugia (pars) Perry in Mitth. nat. Ges. Bern, 1849, p. 45. Centropyxis Stein in Abh. K. Bohm. Ges. Wiss. X (1859), Berichte, p. 43. Echinopywxis Cuaparipg and Lacumann Etudes Inf. et. Rhiz. 2 (1859), p. 447. 132 BRITISH FRESHWATER RHIZOPODA. Test discoid, circular, or oval, with an excentric orifice ; obtusely rounded posteriorly, where it is also thickest, thinning off towards the opposite edge, near which the mouth is situated. Mouth circular or oval, entire or with a sinuous or lobate border; the test furnished with a variable number of conical or curved, sometimes bifid, spines, its substance chitinous, ex- hibiting various shades of brown, or almost colourless; sometimes covered with extraneous elements (sand- grains, etc.) and without spines. The protoplasm colourless ; pseudopodia digitate. Leidy considered Centropyzis to be distinctly separated from Aicella, while on the other hand it appears closely related with Diflugia, through D. coustricta. The relation is almost too close to justify the retention of the latter among the Diffluqie. The priority of Centropyais over Hechinopyris is doubtful, but Stein’s paper was vead in 1857, and his name (Crutropyvis) is the more appropriate one. 1. Centropyxis aculeata (Ehrenb.) Stein. (Plate XVI, figs. 10-14.) Arcella acileata Kurenpere in Abh. K. Akad. Wiss. Berlin, 1830 (1832), p. 40; op. cit. 1851 (1882), p. 91; op. cit. 1841 (1842), p. 368, t. iii, f. 5; Infus. (1838), p. 133, t. ix, f. vi; in Ber. K. Akad. Wiss. Berlin, 1847, p. 477 ; and op, cit. 1853, p. 255; Prrrcnarp Hist. Infus. (1842), p. 169, t. ii, ff. 92-94; new ed. (1852), p. 211, t. u, ff. 92-94; and ed. 4 (1861), p. 555; Barey in Smithson. Contrib, II (1851), art. 8, passim; ArcuEr in Q. J. Micr. Sci. VI, ns. (1866), pp. 185, 186. Areellina aculeata Canton in Ann. Nat. Hist. (1) IX (1842), pp. 362, 493. Difugin aeuleata Perry in Mitth. nat. Ges. Bern, 1849, pp. 45, 162, and Kenntn. kleinst. Lebensf. (1852), p. 186; Lurmy in Proc. Acad. Nat. Sci. Phil. 187-4, p. 14; Mager in Atti Soc. Ital. XXT (1879), p. 319. Ceutropyris aculeata Stun in Abh. K. Bohm. Ges. Wiss. X (1859), Ber. p. 43; Lumpy Freshw. Rhiz. N. Amer. (1879), p. 180, t. xxxi, ff. 1-82; t. xxxn, ff. 29-34; in Proce. Acad, Nat. Sci. Phil. 1879, p. 163; and op. ef. 1880, CENTROPYXIS ACULEATA. 133 p. 388; Hircucock Synops. Freshw. Rhiz. (1881), p. 28; Verspovsky in Sitz.-ber. K. Bohm. Ges. Wiss. 1880 (1881), p. 136, and Thier. Org. Brunn. Prag (1882), pp. 32, 42, t. iii, ff. 8-14; TarAnex in Sitz.-ber. K. Bohm. Ges. Wiss. 1881 (1882), p. 229; Bonron in Midl. Nat. IX (1886), p. 174; Warreteces in Proc. Linn. Soc. N. 8. Wales (2), I (1886), p. 501; Fretpr in Proc. Acad. Nat. Sci. Phil. 1887, p. 122; Harvey in Amer. Nat. XXII (1888), p. 78; Zacwarias in Biol. Centralbl. IX (1889), p. 60, etc. ; Pewarp in Mém. Soc. Phys. Genéve, XXXI, no. 2 (1890), p. 149, t. v, ff. 21-37; in Arch. Sci. Phys. XXVI (1891), p. 148; in Rev. Suisse Zool. VII, 1 (1899), p. 40, etc., t. iv, ff. 1-4; op.ctt. IX (1901), p. 237; and Fanne Rhiz. Léman (1902), p. 302, ff.; Gruper in Zacharias’ Tier- welt Siisswass. I (1891), p. 139, f. 16, no. 5; Perry in Proc. Amer. Soc. Micr. XII (1891), p. 95; Voxtrzkow in, Zool. Anzeig. XIV (1891), p. 225; Casu in Trans. Manch. Micr. Soc. 1891 (1892), p. 51; Lorp in Trans. Manch. Micr. Soc. 1891 (1892), p.57; LevanpeEr in Zool. Anzeig. XVIT (1894), p. 210; [Crate] in Amer. M. Micr. Journ. XVIII (1897), p. 101; Frenzet Mikr. Fauna Argent. I, Prot. 4 (1897), pp. 137, 148, t. x, ff. 14, 15, in Bibl. Zool. IV; Dapay Mikr. Siisswass. Ceylon (1898), pp. 5, 9; Ruvumster in Arch. f. Entwick. VII (1898), p. 277, £. 70; Isszez in Atti Soc. Torino, XXXVI (1901), pp. 64, 68, 273; G. S. Wzsr in Journ. Linn. Soc., Zool. XXVIII (1901), p. 815, t. xxix, ff. 15, 16; op. eit. XXIX (1908), p. 109; and in Ann. Scott. Nat. Hist. 1905, pp. 89, 92. Echinopyzis aculeata Crarartps and Lacumann Etudes Inf. et Rhiz. 2 (1859), p. 447; Carrur in Ann. Nat. Hist. (3), XIII (1864), p. 29, t. i, f. 8; Parrivr in Trans. Devon Assoc, ITI. (1869), p. 67; Barwarp in Proc. Amer. Assoc. XXIV (1876), p. 241, and in Amer. Q. Micr. Journ. I (1879), p. 83, t. viii, f. 3. Arcella diadema Exrenserc in Abh. K. Akad. Wiss. Berlin, 1871 (1872), p. 259, t. ii, f. 7 (non 8). ? Echinopyais hemispherica Barnarp in Proc. Amer. Assoc, XXIV (1876), p. 242; and in Amer. Q. Micr. Journ. I (1879), p. 84, f. 2. Centropsis [male pro Centropyxis] aculeata Parona in Boll. Scient. I, an. 2 (1880), pp. 47, 48. Arcella (Echinopyxis) aculeata Grirritus & Hunrrey Micr. Dict. ed. 4 (1883), p. 70, t. xxx, f. 140. Echinopyxis australis LuxpENFELD in Proc. Linn. Soc. N. 8, Wales, X (1885), p. 724. 134 BRITISH FRESHWATER RHIZOPODA. Test chitinous, variable in size and contour; usually carrying from four to six well-developed, curved, and occasionally bifid spines; opaque or semi-trans- parent, with an irregularly margined orifice, and not infrequently covered wholly or partially with fine sandy particles, or diatom shells; the excentric mouth being always at the shallow extremity. Hndo- plasm and pseudopodia as in Difflugia; the latter sometimes knotted or branching. When encisted the protoplasm forms a spherical ball in the thicker part of the test; it is filled with granular matter and green or colourless globules. Dimensions variable: Diameter of test 110-150 p; length of spines 20 or more. Diameter of mouth 50-60 p. j In ponds and ditches and amongst Sphagiwm and wet moss, associated with Difflugia, etc. ; frequent. The species may readily be distinguished from Difflugia constricta by its larger size and more ex- panded outline, as well as by the branching of the pseudopodia. It is usually most plentiful amongst wet Sphagnum in swampy ground. Examples occurring in such situations are, as a rule, free from extraneous matter, except diatom shells, of which in some cases they appear as if built up. Those without incrusta- tions have an irregular and delicate mesh-work on the chitinous surface and usually have the longest spines. Examples vary greatly in size. West (in ‘ Journ. Linn. Soc.,’ Zool., vol. xxviii) records individuals from Athry Lough, W. Ireland, measuring 450 4 without the spines. The transparent chitinous test sometimes exhibits a cancellated or punctated surfacing. Some Terrington Carr examples were found by the same author to be of a pale yellow colour and minutely scrobiculate. The scrobiculations were irregularly disposed, being scattered more or less in groups, and between them were numerous much smaller punctulations. CENTROPYXIS ACULEATA. 185 Var. spinosa var. nov. (Plate XVI, fig. 15, and fig. 26 in text.) Test purely chitinous, without adherent sand-grains, semi-transparent ; yellowish brown when young, turn- ing to a darker brown with age (like Arcella vulgaris), and often partially or wholly covered with diatom- frustules. The mouth lobate or of unequal outline, variable in width, the margin sometimes slightly in- verted. Spines variable in number and also in length, of the same substance as the test, and frequently curved. Fic. 26.—Centropyais aculeata var. spinosa. u,a well-developed form ; b, an example showing variation; c, lateral view of this form (in outline). From Dunham Marsh, Cheshire. x 260. Dimensions: Diameter in face view 120-140 p; greatest width in side view 30-40 pm. In Sphagnum; frequent in Cheshire and North Wales. This variety seems to have been regarded by most observers as indistinguishable from the type. We are, however, of opinion that the structure of the test, its more numerous spines, and particularly the lobate 136 BRITISH FRESHWATER RHIZOPODA. mouth, are characters which justify the separation of this form under a varietal name. In our experience it most frequently occurs in wet Sphagnun. The variety is further distinguished from the type by its being more compressed and altogether more delicate in appearance. With regard to C. aculeata and its varieties, it must be confessed there is not a little ambiguity. Forms are met with, chiefly in Sphagnum, which differ widely not only from the type, but also from each other, both in size and contour. Some are scarcely larger than average examples of Difflugia constricta, and differ so httle from that species as to be almost indistinguish- able; there is, in fact, a gradation of forms connecting the two species (C. aculeata and D. constricta), so numerous that it would be a difficult and not very profitable task to single them out for specific mention. Var. ecornis (Ehrenb.) Leidy. (Plate XVI, fig. 16.) Arcella ecornis Wurenserc in Abh. K. Akad. Wiss. Berlin, 1841 (1843), p. 368, t. i, f. 9; t. ili, f. 46; in Ber. K. Akad. Wiss. Berlin, 1845, p. 307; op. cit. 1848, pp. 215, 226; and op. cit. 1853, p. 178; Prircuarp Hist. Infus. new ed. (1852), p. 212, and ed. 4 (1861), p. 555. Arcella diadema (pars) Exrensrre in Abh. K. Akad. Wiss. Berlin, 1871 (1872), p. 259, t. iii, f. 8. Centropyxis ecornis Lurpy in Proc, Acad. Nat. Sci. Phil. 1879, p. 163; TarAnex in Sitz.-ber. K. Bohm. Ges. Wiss. 1881 (1882), p. 229; Vespovsxy Thier. Org, Brunn. Prag (1882), pp. 32, 48, t. iii, ff. 1-7; Fretpz in Proc. Acad. Nat. Sci. Phil. 1887, p.122; Lorp in Trans. Manch. Mier. Soc. 1891 (1892), p. 57; Fruwzet Mikr. Fauna Argent. I, Prot. 4 (1897), p. 146, t. ix, ff. 18-15, in Bibl. Zool. IV. Centropywis aculeata var. ecornis Leipy Freshw. Rhiz. N. Amer. (1879), p. 181, t. xxx, ff. 20-84; t. xxxi, ff. 88, 34; t. xxxi, ff. 35, 386; Punarp in Mém. Soc. Phys. Geneve, XXX, no. 2 (1890), p. 150, t. v, ff. 45-48; G.S. West in Journ, Linn. Soc., Zool. XXVIII (1901), p. 317. Test of the same general structure as the type, but usually smaller; spineless. CENTROPYXIS ACULEATA. 137 Less common than the type, but not infrequently met with in swampy ground. Very abundant amongst damp moss on limestone rocks, Ingleton; also near Bowness, Westmoreland (G. S. West). This variety seems to be the Arcella ecornis of Khrenberg, properly removed by Leidy from that genus to Centropyxis as a variety of C. aculeata. Ex- cept for its usually smaller size it might be regarded as typical C. aculeata deprived of its spines. From Arcella it differs essentially in its test, which, as a rule, is heavily encrusted with sand-grains; whilst from C. levigata Penard, it is at once distinguished by the character of the orifice, which is plain and not invaginated. 2. Centropyxis levigata Penard. (Fig. 27.) Centropyais levigata PenarD in Mém. Soc. Phys. Genéve, XXXI, no. 2 (1890), p. 151, t. v. ff. 42-44, 49-55, and Faune Rhiz. Léman (1902), p. 306, ff, and p. 666. Test in face view nearly circular, usually slightly compressed on one side, composed of chitinous material, and covered with irregular surface-scales and an .ad- mixture of fine sandy or muddy particles, causing opacity ; the mouth obliquely invaginated, its outer margin broadly rounded, the orifice (terminating the inverted neck) excentric and generally invisible. In side view the outline of the test is nearly hemispher- ical, being broader at the posterior extremity. In this aspect it has some resemblance—helped by the surface-markings—to some forms of Difflugia arcula, from which, however, the character of the mouth and the inverted neck at once distinguish it. Dimensions: Diameter in face view about 100 uw (120-135 p, Penard). In Sphagnnm; at Dunham and Chelford, Cheshire, and near Abergynolwyn, North Wales. 1388 BRITISH FRESHWATER RHIZOPODA. The test of C. levigata is not infrequently met with in Sphagnum from the localities indicated, but from its general opacity and resemblance to full-sized in- dividuals of Diflugia wrcula, is liable to be passed by. The rounded margins of the oral orifice, and the obliquely inverted neck, are sufficiently characteristic features. Fie. 27,.—Centropyzis levigata (face and lateral views). In Sphagnum from Dolgoch, Merionethshire. x 260. Penard describes two other species of Centropyris, C. delicatula and C. arcelloides, both smaller than that under notice, and having more or less external resemblance to Arcellu vulgaris. They differ from C. levigata im the structure of the mouth and other features. Genus ARcELLA (see pp. 118-121). Arcella vulgaris var. compressa var. nov. (Fig. 28.) Arcella vulgaris (pars) Leiy Freshw. Rhiz. N. Amer. (1879), pl. xxvin, ff. 6, 7. Arcella artocrea Penarp Faune Rhiz. Leman (1902), p. 405, ff. (Non A. artocrea Leidy, 1879.) Test composed of thin chitinous membrane, yellowish brown and semi-transparent, becoming darker with age, and faintly punctated. In face view discoid, irregularly oval, or sub-quadrate with rounded angles, never truly circular; with a centrally-situated, com- paratively small oval mouth. In side view the crown ARCELLA VULGARIS. 139 is compressed, its surface is parallel to the base and almost half its width. The lateral margins form six or eight obtusely-angular facets, the divisions of which are faintly distinguishable in face view; the neck is broadly mverted and extends upwards into the cavity of the test to about one third the distance separating the base from the crown. Dimensions: Diameter in face view averaging 100 to 120 »; from base to crown in side view about 45 p. In Sphagnum from Dolgoch, Merionethshire, Aug., 1905. This variety is one of the numerous forms figured by Leidy under the general name of Arcella vulgaris, but is so distinct, and so evidently a permanent form, that its separation as a variety approaching A. angulosa. is desirable. Penard figures it (oc. cit.) as a European form of A. artocrea, but this species, according to Leidy, though pitted with surface-depressions, has an arched crown. G.S. West also (‘ Journ. Linn. Soc.,’ Zool., vol. xxviil) figures it thus. Arcella vulgaris var. compressa is rare. We have only met with it in Merionethshire. Fic. 28.—Arcella vulgaris var. compressa (face and lateral views, in outline). In Sphagnum from Dolgoch, Merionethshire. x 260. 140 BRITISH FRESHWATER RHIZOPODA. Order Amaprna, Family Rericunosa. Genus Cunamypomyxa (see pp. 91-94). 2. Chlamydomyxa montana Ray Lankester. (Figs. 29-32.) Chlamydomyxa Ray Lanxusrer in Nature, XXXIV (1886), . 408. Gems montana Ray Lankxesver in Q. J. Mier. Sci. XXXIX, n.s. (1896), p. 233, tt. xiv, xv; Pznarp in Arch. f. Protisten-Kunde, IV (1904), p. 296, ff. Chlamydomyzxa labyrinthuloides (pars) Hrzronyuus in Hed- wigia, XXXVIT (1898), t. u, ff. 28-25; JunKInson in Q. J. Micr. Sci. XLII, n.s. (1899), f. v. Body initially a rounded or ovoid particle of yellow- ish-green or brownish protoplasm, about 50 mw in dia- meter, resembling an Amaba at rest; the endoplasm densely crowded with pigmented corpuscles, rendering it nearly opaque; surrounded by a light-greyish or colourless border of granular-looking ectoplasm, from which, at different points, when the animal begins to move, pseudopodia are slowly emitted. Usually the body becomes ellipsoid, and pseudopodal development takes place at each extremity; the body gradually elongates and the ribbon-like pseudopodia break forth into extremely fine filaments, ‘apparently extruded from the general mass” (Lankester). They may be straight and rigid, or gently curved, and are susceptible of movement from side to side. The pseudopodia occasionally anastomose, and the fine filaments also have a tendency to unite; and they may sometimes branch or bifurcate. The animal is sensitive to any disturbance. When active it will vary in form from sub-spherical to ovoid or sub-triangular, the ends, or angles, being the points where the larger masses of filaments originate. Simultanéously with these move- CHLAMYDOMYXA MONTANA. 141 ments, and probably as a result of them, numerous vacuoles (non-contractile) appear in the substance of the ectoplasm about the bases of the pseudopodia. During the activity of the animal there is a constant: movement of minute fusiform colourless bodies (similar to, but smaller than those observed in C. labyrinthu- loides), up and down the finely-attenuated threads, the precise function of which (as in C. labyrinthuloides) has not been satisfactorily determined. Prof. Lankester Fie. 29.—Chlamydomyxa montana. An individual extended and active. Chelford ; September, 1905. x about 400. was of opinion that they might consist of nuclear substance, “the particles of a fragmented scattered nucleus,’ but more recent researches by Dr. Penard have resulted in the discovery of true nuclei (which are numerous) in the pigmented substance of the endo- plasm. They are spherical, very pale, and_average 2-75 w in diameter. Spherical cists are formed, several of which may be enclosed in a common cellulose envelope. A fragmentation of the plasma takes place, and there is a formation of secondary cists; these are liberated in due time, and undergo separate develop- 142 BRITISH FRESHWATER RHIZOPODA. ment; and each exhibits in its own substance the elements characteristic of the parent, with true nuclei. The primary cist does not always proceed to fragmen- tation; the enclosed protoplasm may burst its envelope and resume active life (Penard). Dimensions : Diameter of body (initial state) about — 50 w; length when extended (ovoid) 100-150 »; inclu- sive of the pseudopodia 300 p or over. In a boggy pool at Chelford, Cheshire, associated with Cochliopodia, Hyalodiscus +ubicundus, and other Rhizopoda, amongst floating vegetation, Sept., 1905. Our practical acquaintance with this species is con- fined to two or three individuals met with whilst the preceding pages were passing through the press. With such inadequate material there was no opportunity for careful study, but this is the less to be regretted as the descriptions given by Ray Lankester and Penard are so exhaustive. For the particulars here given we are largely indebted to these authors. Chlamydomyea montana first became known through the investigations of Professor Lankester. Repeated search for (C. labyrinthuloides was fruitless, but in August, 1886, he succeeded in finding on Sphagnun in ditches, cut in a bog which occupies a clearing in the pine-wood at Pontresina, the form afterwards described under the name of C. montana. It was met with by -him on two subsequent visits to Switzerland. In each case the Sphagnum was old and in a state of incipient decay. It is to be noted that neither in our own experience, nor in that of Dr. Penard, was the animal met with m Sphagnum. The latter discovered it near Geneva, in marshy ground, associated with a species of aquatic Hypuum. In our only known English locality it was found in a pool, amongst some flocculent surface-vegetation which harboured a great variety of Desmidiz, as well as much rhizopodous life, including such species as Hyalodiscus rubicundus, Cochliopod ian bilimbosum, Diflugia corona, D. amphora, and various CHLAMYDOMYXA MONTANA. 143 Amwbx, showing that Sphagnum is not essential to its existence. Moreover Dr. Penard was more fortunate than Dr. Lankester in being able, from the abundant examples which he found, to trace its life-history. Dr. Lankester, in his article in the ‘Quarterly Journal of Microscopical Science,’ was able to give a full description of C. montana in its active phase. Its most striking peculiarity was found in the threads, and the “ oat-shaped corpuscles’ by which they were “a b c 30 31 Fia. 30.—Pseudopodal filaments of C. montana: a,an entire filament ; b, a portion of the same, more highly magnified ; ¢, a filament on which is a mass of ectoplasm, containing vacuoles. After Penard. Fie. 31.—A fragment of the body of C. montanw, under pressure, show- ing contained granules, vacuoles, and two nuclei (); very highly magnified. After Penard. traversed (fig. 30); these corpuscles being, according to Archer, one of the leading characteristics of his U. labyrinthuloides, and comparable to the nucleated spindle-shaped bodies which travel upon the threads of the Labyrinthula of Cienkowski. The threads are of extreme tenuity. “I never,’ he says, “saw any thread either fuse’with a neighbouring thread or divide into two. It appears to me (but the observation is difficult) that when two threads come together they may be very closely apposed, but nevertheless retain 144 BRITISH FRESHWATER RHIZOPODA. their distinctness ; and conversely that when a thread seems to divide into two, longitudinally, the case is really one of separation of two pre-existing threads.” His general conclusion was that the threads do not form a dendritic branching figure, or a network, but are merely apposed so as to form one less expanded, or, to speak more accurately, an apparent meshwork, and when more straightened and separated from one another, an apparent tree-like structure, the appear- ance in both cases being illusive. Dr. Penard, however, having given close attention to the filaments and their behaviour, is of opinion that a real fusion is effected. The power of each filament to bifurcate he also placed beyond question. With regard to the fusiform hyaline corpuscles which travel along the threads, Dr. Lankester says: “The movement of the oat-shaped corpuscles is the most interesting and characteristic feature presented by Chlamydomyra. It must be distinguished altogether from the straightening and expanding movement of the mass of filaments; at the same time, it is not manifested until the filaments have become—some at least of them—straightened and free. Then as such a filament spreads itself, and as it were slowly pushes itself forth in a straight line, first one, then another, and finally many of the oat-shaped corpuscles are seen to advance along it. They move slowly in one direc- tion as a rule, stopping sometimes after a considerable advance, and then resuming movement. They do not all travel at the same rate on one filament. I saw on several, one corpuscle overtake another and glide over the back (so to speak) of its more slowly-moving com- panion, and advance in front of it.” He was of opinion that the movement was produced by an exceedingly delicate coat of hyaline protoplasm. These minute bodies differ from those of CO. labyrinth- uloules in_ being considerably smaller, and generally ovoid. They are colourless, and Penard says resist the action of carmine and other reagents. Their CHLAMYDOMYXA MONTANA. 145 average length scarcely reaches 2p. They never, on meeting, fuse one with another. The endoplasm of C. montana is filled with minute pigmented corpuscles. It is these which give the body its yellow-brown colour. Diatoms and small alge are also often present in the general mass. Dr. Penard found cists of O. montana of two kinds— namely, temporary cists, and cists proper, in which the organism maintains a latent existence for longer or shorter periods. The temporary cists, about 2p in diameter, have a transparent membranous envelope, usually colourless, but occasionally light yellow, and with a double contour. They are generally ovoid. The true cists are spherical; two or three together are sometimes found occupying'a common cellulose envelope. Whilst C. labyrinthuloides rarely abandons its envelope, C. montana, in its active life, is invariably: naked, and when encisted occasionally escapes from its cist (fig. 32), a mass of plasma issuing from an aperture— giving the organism the appearance of a testaceous rhizopod, with amoeboid movements, and emitting filamentous pseudopodia rather copiously. More fre- quently there is a fragmentation of the contents of the cist, and from 20 to 40 globular secondary cists, about 18 w in diameter, are liberated, to develop ultimately into living individuals, identical with the parent, but extremely minute. ‘Fie. 32.—C. montana. A young individual issuing from its cist; highly “ magnified. After Penard. 10 146 INDEX OF SPECIES, ETC., DESCRIBED IN Vou. I. Synonyms in italics. PAGE PAGE Ameba diffluens Maggi 43 | Amoeba princeps Carter 50 guttula Maggi 55 ? princeps Czerny 75 princeps Maggi Ad proteus (Pallas) Leidy . 41 radiosa Maggi 66 var. granulosa Cash . 48 verrucosa Maggi 60 ? proteus Brayl. . 75 Amiba Bory . 40 quadrilineata Carter 59 brachiata Duj. 65 radiosa Ehrenb. . 64 difluens Duj. 43 Reselii Pritch. . . 43 divergens Bory 41 Reselit (?) Carter. 43 guttula, Duj. 54 sabulosa Leidy 79 Keeselii Crev. 43 striata Penard . . 53 limax Duj. 57 ? striolata Perty . 53 Mullert Bory 42 terricola Greeff . 60 princeps Duj. 43 verrucosa Hhrenb. . 58 radiosa Duj. 65 verrucosa Leidy . . 53 Reselvi Bory 41 villosa Wallich 50 verrucosa Duj. 59 villosa Archer 83 Ameeba Ehrenb. . 40 villosa Slack i) 49 actinophora Auerb. 48 vitrea Penard . 68 brachiata Froment. 65 | AM@BINA 3 . 36 chaos Leidy : 45 | Amphizonella Greeft 129 communis Duncan 45 flava Greeff 130 difiuens Ehrenb. . 42 | Arcella Hhrenb. 117 gorgonia Penard . 52 aculeata Ehrenb. . . 132 guttula Dy. 54 angulosa Perty . . 121 lateritia Fresen. . 96 artocrea Leidy 127 lawreata Penard . 80 costata Penard . 121 limax Duj. . 57 dentata Ehrenb. . . 125 limicola Rhumbl. 56 diadema Ehrenb. . . 133 natans Perty ‘ . 59 discoidea Ehrenb. 122 oblonga Schmarda 43 discoides Ehrenb. . 122 papillata Mereschk. . 60 ecornis Ehrenb. . 136 pilosa Cash : . 62 gibbosa Penard . . 121 polypodia Max Sch. . 67 hemispherica Perty . 120 princeps Ebrenb. . . 42 mitrata Leidy . 124 INDEX. 147 PAGE PAGE Arcella Okeni Perty . 126 | Dactylospheria ads patens Clap. & Lachm. 120 Bitsch. . ‘ 68 peristicta Khrenb. . 128 radiosa Laness. 66 stellaris Perty 126 radiosum Bitsch. . 66 stellata Ehrenb. 126 | Dactylospherium Hertw. & viridis Perty 120 Less. 64 vulgaris Ehrenb. . . 118 polypodium (Maz Sch.) var. angulosa (Perty) Biitsch. : 67 Leidy. . 121 radiosum (Hhrenb.) Biitsch. 64 var. compressa Cash 188 vitreum Hertw. & Less. . 68 var. discoides Issel 123 | Der Kleine Proteus Résel 41 var. gibbosa (Penard) Diflugia Perty 131 G. S. West . 121 | Diflugia Wallich 117 ARCELLIDA 115 aculeata Perty 132 Arcellina Canton 181 arcella Wallich . 120 Arcellina Carter 117 | Echinopyxis Clap. & Lachm. . 131 aculeata Canton 132 aculeata Clap. & Lachm.. 133 dentata Carter 126 australis Lendenf. . 133 vulgaris Carter 120 ? hemispherica Barnard . 133 Archerina Ray Lank. . 112 | Gymnophrys Cienk. 86 Boltoni Ray Lank. 113 cometa Cienk. 86 Astrameba radiosa Vejdovs. 66 | Guttulidium guttula Frenz. 55 Biomyxa Leidy 88 | Heliophrys Greeff 109 vagans Leidy . 88 variabilis Greeff . 110 Centropsis aculeata Parona . 133 varians G. S. West 110 Centropyxis (Ehrenbd.) Stein . 131 | Heterophrys Archer . 109 aculeata Stein 132 ? myriapoda Archer 110 var. ecornis (Ehrenb.) varians F, BE, Sch. . 110 Leidy . 186 | Hyalodiscus Hertw. & Less. . 106 var. spinosa Cash 135 guttula Blochm. . 55 ecornis Leidy 1385 limax’Blochm. 57 levigata Penard . 137 rubicundus Hertw. & Less. 106 Chaos Linn. 40 | Leptophrys vorax Zopt . 102 protheus Linn. 41 | Lithameba Ray Lank. 81 Chlamydomyxa Archer 91 discus Ray Lank.. 81 labyrinthuloides Archer . 92 | Loposa 39 labyrinthuloides Hieron. . 140 | Mastigameeba F. E. Sch. 69 montana Ray Lank. 140 aspera F'. H. Sch.. 70 ? Cochliopodiwm actinophorum var. cestriensis Cash 72 Penard 48 ramulosa Kent . . 73 CoNCHULINA . . 87 | Nuclearia Cenk. . 109 Dactylosphera Lene ne conspicua G. S. West . 112 Lank. : 68 delicatula Cienk. . 109 148 INDEX. PAGE PAGE Ourameba Leidy . 83 | Saccamceba verrucosa Frenz. 60 lapsa Leidy . 84 villosa Frenz. ; . 50 villosa Ray Lank. 84] SaRcopina . . . 36 vorax Leidy 5 . 88 | Thecameba quadripartita Pelobius Greeff ; . 73 Froment. . d . 60 Pelomyxa Greeff . 73 | Trichameba hirta Froment. . 50 palustris Greeff . 74 | Vampyrella Cienk. . 95 villosa Letdy . 79 flabellata Cash 103 Penardia Cash . . 89 gomphonematis Heck. 105 mutabilis Cash . 90 lateritia (Fresen.) Leidy 96 Plakopus F. HE. Sch. 106 pedata Klein . 107 ruber F. HE. Sch. 106 sptrogyrz Cienk. . . 96 Proteus O. F. Mull. 40 ? variabilis Klein . 102 erystallinus Schrank 41 vorax Cienk. . 102 difiuens O. F. Mull. 41 | VAMPYRELLIDA 94 Pseudochlamys Clap.d Lachm. 129 | VibrioO. F.Mull. . 40 patella Clap. & Lachm. 129 proteus O. F. Mill. 4] RETICULOSA 85 | Volvow Linn. . 40 RHIZOPODA 36 chaos Linn. 41 Saccameba limax Frenz. 57 proteus Pallas 41 PRINTED BY ADLARD AND SON, LONDON AND DORKING. EXPLANATIONS OF THE PLATES. ( 150 ) c.v. Contractile vacuole. n. Nucleus. Plate 1 Fias. PLATE I. 1,2. Ameeba proteus (Pallas) Leidy. (p. 41) Forms of a 3. A, 4-6. A. 7-10. A. single individual. In fig. 1 the ectoplasm is repre- sented as seen adhering to the cover-glass. Pond at Bangley, Cheshire. x about 400. proteus var. granulosa Cash. (p.47) In rapid move- ment. Hale Moss, Cheshire. x abont 400. proteus. Fig. 4.—Common pond form, the plasma- body appearing in two nearly equal masses with a connecting isthmus in which the contractile vacuole appears centrally situated. Figs. 5 and 6.—Two views of a smaller pond form, containing a Navicula. All x 800. actinophora Auerb. (p. 48) Figs.7 and 8—Active and quiescent states. Pond at Chelford, Cheshire. Figs. 9 and 10.—Another individual exhibiting the same phases. From the same pond. All x 450. sh ae Plate 2 PLATE II. Ameba villosa Wallich. (p. 50) Fies. 1, 2. Two views of a large and active individual, the endo- plasm containing various alge and diatoms, besides chlorophyllose corpuscles. In fig. 2 the posterior villous organ is obscured. Pond at Baguley, Ches- hire. x 300. 3,4. Two views of another individual. From the same locality. x 300. 5, 6. A young individual. In fig. 6 the form represented was assumed upon agitation of the cover-glass. x 300. 7. Another example, containing a large Navicula. x 300. PA QE J Cash, del. AS. Huth, lith Plate 3 Figs. lla. 3-5. 6-7 a. 8-11. 12. PLATE III. Ameba limae Duj. (p. 57) Fig. 1.—Ordinary form. Dunham Marsh, Cheshire. x 300. Fig. 1 a— Details of characteristic caudal appendage. After Penard. A. proteus var. granulosa Cash. (p. 47) Hale Moss, Cheshire. x about 400. A, gorgonia Penard. (p. 52) In Sphagnum, pondside, Chelford, Cheshire. x 300. Fig. 3—In a resting state. Fig. 4.—Active movement commenced, most of the pseudopodia withdrawn. Fig. 5.—The whole of the pseudopodia withdrawn, the animal exhibiting remarkable contortions during progression. A, striata Penard. (p. 53) Figs. 6 and 7.— Two indi- viduals differing in size. Pond at Northenden, Cheshire. x 400. Figs. 7a, b—The contractile vacuole (a peculiar form). After Penard. Dactylospherium radioswm (Ehrenb.) Biitschh. (p. 64) Figs. 8 and 9.—An individual of unusual form. In fig. 8 three arms are extended irregularly, each from a broad base ; in fig. 9 one arm is partially retracted. In Sphagnum, Cheshire. x 300. Fig. 10.—The same form (?), after West. Fig. 11.—An uncommon inert form, exhibiting attenuated pseudopodia which are bent and in some cases spirally twisted. In Sphagnum, Knutsford Moor, Cheshire. x about 200. D. polypodiwm (Max Sch.) Biitschli. (p. 67) After Hertwig and Lesser. moO chro P TATERE Te Plate 4 Fias. PLATE IV. 1-5. Ameba pilosa Cash. (p.62) Figs. 1-3.—Typical form, 6-11 as seen in three positions. Chelford, Cheshire. x 300. Figs. 4 and 5.—A possibly distinct form having the same pilose character, but of more sluggish habit, with a posterior lobe, and with the endoplasm more densely granular. The punctula- tions on the surface of the posterior lobe represent spiculee which stand erect, presenting their extremi- ties to the eye. Pond at Fearnhead, Lancashire. x 3800. . Dactylospherium radiosum (Khrenb.) Biitschli. Figs. 6-8.—Phases of a single individual, representing a common type; in fig. 8 in rapid movement, with all the pseudopodia retracted. Dunham Marsh, Cheshire. x 800. Figs. 9 and 10.—lLess frequent forms; 9, with numerous rigid, elongated, and sharply- pointed pseudopodia; 10, a large and peculiarly radiate example. Dunham Marsh. x 400. Fig. 11.—Another form, after West. x 480. 2. D. polypodiwm (Max Sch.) Bitschli. (p. 67) After Penard. Plate 5 PLATE V. Figs. 1-84. Amoeba verrucosa EKhrenb. (p. 58) Fig. 1—An in- dividual in the resting phase, enclosing a rotifer. Perwick Bay, Isle of Man. x 300. Figs. 1 a-c.— A single young individual, general form subspherical, the body translucent, its surface wrinkled. In Sphagnum, Cheshire. x 300. Fig. 2.—An adult individual in the resting phase, containing much partially-digested food. Isle of Man. x 300. Fig. 3.—An individual seen during greatest activity. Heatley, Cheshire. x 800. Fig. 3a.—Nucleus, after Penard. More highly magnified. 4, A. guttula Duj. (p. 54) Common form occurring in ponds amongst surface vegetation. x 400. 5. Lithameba discus Ray Lank. (p. 81) Outline sketch, after Ray Lankester. 6. Ourameba voraw Leidy. (p. 83) After Leidy. x 200. PA a5 J. Cash del Plate 6 PLATE VI. Figs. 1-3. Mastigameba aspera F. KE. Sch. (p. 70) Fig. 1L— Ordinary appearance of an adult during forward movement Pond at Chelford, Cheshire. Fig. 2.— An individual which, after passing through a variety of mutations, ejected a quantity of effete matter at the point a. The flagellum is not visible, though in the normal state it was distinctly seen (as in fig. 1). Fearnhead, Lancashire. Fig. 3.—A smaller example showing variation from the type. All x 400. 4. M. aspera var. cestriensis Cash. (p. 72) Northen Etchells, Cheshire. x 400. 5. M. aspera. An attitude not infrequently assumed when the animal is resting, showing a resemblance to some figures of Dactylospheriwm vitreum Hertw. & Less. Chelford, Cheshire. x 400, ‘ 6. M. ramulosa Kent. (p. 73) Typical form, after Saville Kent. x 400. Plate 7 Figs. PLATE VII. 1-3. Pelomyxa palustris Greeff. (p. 74) Fig. 1.—Ordinary 4-6. P. condition during active movement. Pond at Northen Etchells, Cheshire. x about 100. Figs. 1 a—-d.— Phases in development from amcebule, as observed by Greeff. Fig. 2—A young individual in resting state, showing internal structure; after Greeff. x about 60-70. Fig. 3.—An unusual phase of resting state, the plasma-body forming a sub-spherical mass with a fringe of fine hyaline pseudopodia. x about 150. villosa Leidy. (p. 79) Fig. 4—Ordinary condition during activity. Fig. 5—A somewhat larger indi- vidual in the same condition. Fig. 6.—A portion of the latter after undergoing various changes. By lateral extension of the body the posterior lobe became obliterated and the villi were spread out along the margin until the normal condition was reverted to. All x 250. PLATE VIL. PELOMYXA. J.Cash, del Plate 8 PLATE VIII. Fies. 1,2. Gymnophrys cometa Cienk. (p. 86) Fig. 1—An ex- ample from wet Sphagnum, Lindow, Cheshire. x 300. Fig. 2.—After Penard. 3, 4. Biomyxa vagans Leidy. (p. 88) Views of a single indi- -vidual showing forms assumed during active move- ‘inent. In tufts of moss on moist rocks, Perwick Bay, Tsle of Man. x 300. PLATE VIL. ae ee GYMNOPHRYS ano BIOMYXA. PWM Trap, 1mpr. JCash, del.” Plate 9 PLATE IX. Penardia mutabilis Cash. (p. 90) Figs. 1-5.—Different phases of a single individual. Figs. 1 and 2,—The animal in active movement, the disposition of the pseudopodal filaments constantly changing. Figs. 3-5.—After capture of a rotifer; 3, the prey enveloped by sarcode processes; 4, most of the pseudopodal fila- ments withdrawn before complete absorption of the rotifer ; 5, after its absorption, the rotifer being enclosed in the body-mass, and invisible. In wet Sphagnum, Epping Forest. x about 300. ] _ Plate 10 Figs. 1-4. Rone 6, 7. 10. PLATE X. Vampyrella lateritia (Fresen.) Leidy. (p. 96) Ordinary form. Marshy pools, Cheshire. x 300. Fig. 1. —Showing capitate and pseudopodal rays. Fig. 2.— The same individual attached to a Conferva filament. Fig. 3.—The filament broken at a joint, one cell being emptied of its chlorophyl. Fig. 4.—After two cells have been cleared, showing the position in which the cells were left. Liberation of a sporozoon, the pseudopodia of which are sharply pointed. x 300. Two views of the same sporozoon after complete separa- tion, exhibiting amoeboid movements and containing a vacuole and an apparent nucleus. (The further development could not be traced.) x 300. . A peculiar condition, the body covered with a mass of external vesicles (some pedunculated). Dunham Marsh, Cheshire. x 450. An individual with two pulsating vesicles, fine radial filaments, and numerous short irregularly-crowded pseudopodia in place of capitate rays. Barking, Essex. x 450. An individual at rest, after attacking a Conferva fila- ment and absorbing the chlorophyl of one segment. Epping Forest. x 3800. ae =e aise fie Plate 11 PLATE XI. Figs. 1-3, Vampyrella lateritia (Fresen.) Leidy. (p.96) Fig. 1. —An individual with pseudopodia fully extended. After West. x 520. Fig. 2.—The same, after attacking a filament of Mougeotia. After West. x 520. Fig. 3.—Slug-like form. After Biitschli. x about 800. 4-6. V. vorary Cienk. (p. 102) Fig. 4.—A plasmodium formed by the union of two separate individuals, of which fig. 5 was one. Pond at Northen Etchells, Cheshire. x 500. Fig. 6.—An individual of un- usual form. After Penard. 7-12. V. flabellata Cash. (p. 103) An individual as seen in various attitudes, during extended observation. Barking, Essex. x 500. 13-15. V. gomphonematis Heck. (p. 105) Fig. 13—An individnal as ordinarily met with amongst floating vegetation. Pond, Cheshire. x 500. Fig. 14.— Another, enclosing a diatom from which it had ex- tracted the chlorophyl. Pond, Cheshire. x 500. Fig. 15.—An example as seen enveloping frustrules of a Gomphonema. From Biitschli, after Heckel. x about 350. PLATE 21. VAMPYRELLA. dCash del. PWM Trap impr. Plate 12 PLATE XII. Nuclearia delicatula Cienk. (p. 109) Fias. 1, 2. Views of a single individual. Fig. 1—Resting phase. Fig 2.—Body extended and in active movement. Each x 450. 3, 4. Resting (3) and active (4) phases of another individual. x 300. 5, 6. Resting (5) and active (6) phases of another individual. x 3800. 7, 8. A young state (?) of this species. x 300. All from ponds in Cheshire. £ i \ y \ i LAt\ LN yy \\ | /} | ; Plate 13 PLATE XIII. Figs. 1. Nuclearia conspicwa West. (p.112) An individual with pseudopodia extended. After West. x 400. 2-6. Hyalodiscus rubicundus Hertw. & Less. (p. 106) Figs. 2 and 8.—Views of single individual. Pond at Northen Etchells, Cheshire. x 500. Fig. 4.— Anterior margin. After Penard. Figs. 5 and 6.— Resting and active states. After Penard. 7. Form of H. rubicundus named Plakopus ruber by F. E. Schulze. After Schulze (reduced). x about 400. 8-11. Phases assumed by an individual probably identical with the above form. Epping Forest. x 500. PLATE XI. NUGLEARIA AND HYALODISCUS. PWM Trap impr. J.Cash del. Plate 14 PLATE XIV. Fias. 1. Chlamydomyea labyrinthuloides Arch. (p. 92) An indi- vidual with widely-extending filamentous pseudo- podia emerging from a cist. After Archer. 2-6. Archerina Boltont Ray Lank. (p. 114) Fig. 2—A colony of irregularly-grouped chlorophyl-corpuscles and protoplasm resulting from tetraschistic division of one original chlorophyl-corpuscle (as fig. 3), the abundant amceboid protoplasm actively ingesting a bacillus filament (a). Fig. 8.— ee ee rors aaa = Se SERRE I = Boge SEE eieieltan te erty So a Gila A 3k Se Sa ONG SSS GSN OC a I OL ee fathers a