10 



PROTOZOA 



Diajardin, Histoire naiurdle des Infusoires, 1841 ; Piitchard, In- 

 fusoria, 1857. 



The general questions relating to protoplasm and to the consti- 

 tution of the Protozoon body as a single cell are dealt with in the 

 following more recent treatises ; — Max Schultze, Ueber den Organ- 

 ismiLs der Polythalamien, 1854, and Ueber das Protoplasma der 

 Shizopoden und Pflanzenzellen, 1863 ; and Engelmann, article ' ' Pro- 

 toplasma" in Hermann's Handworterl/uch der Physiologie, 1880. 



Special works of recent date in which the whole or large groups 

 of Protozoa are dealt with in a systematic manner with illustra- 

 tions of the chief known forms are the following : — Biitschli, " Pro- 

 tozoa," in Bronn's Classen und Ordnungen des Thierreichs, a, 

 comprehensive and richly illustrated treatise now in course of 

 publication, forming the most exhaustive account of the subject 

 matter of the present article which has been attempted (the virriter 

 desires to express his obligation to this work, from the plates of 

 which a large proportion of the woodcut figures here introduced 

 have been selected) ; W. S. Kent, Manual of the Infusoria, 1882 — 

 an exhaustive treatise including figures and descriptions of all 

 species ofFlagellata, Dinoflagellata, CUiata, and Acinetaria ; Stein, 

 Der OrganisTKUs der Infusionsfhiere, 1867-1882; Haeckel, Die 

 Sadiolarien, 1862; Archer, "Resum^ of recent contributions to 

 our knowledge of freshwater Rhizopoda," Quart. Jour, of Micro- 

 scopical Science, 1876-77; Zopf, "Pilzthiere" (Mycetozoa), in 

 Encyklopddic der Natunmssenschaften, Breslau, 1884. 



We shall now proceed to consider the classes and orders of 

 Trotozoa in detail. 



PROTOZOA. 



Characters. — Organisms consisting of a single cell or of' a group 

 of cells not differentiated into two or more tissues ; incapable of 

 assimilating nitrogen in its diffusible compounds (ammonia or 

 nitrates) or carbon in the form of carbonates, except in special 

 instances which there is reason to regard as directly derived from 

 allied forms not possessing this capacity. The food of the Protozoa 

 is in consequence as a rule taken in the form of particles into the 

 protoplasm either by a specialized mouth or by any part of the 

 naked cell-substance, there to be digested and rendered diffusible. 



Grade A. OYMNOMTXA, Lankester, 1878 (64). 



Characters. — Protozoa in which the cell-protoplasm is entirely or 

 partially exposed to the surrounding medium, during the active 

 vegetative phase of the life-history, as a naked undifferentiated 

 slime or viscous fluid, which throws itself into processes or 

 " pseudopodia " of various form either rapidly changing or 

 relatively constant. Food can be taken into the protoplasm in the 

 form of solid particles at any point of its surface or at any pgint 

 of a large exposed area. The distinction into so-called "exoplasm" 

 and " endoplasm " recognized by some authors, is not founded on a 

 permanent differentiation of substance corresponding to the cortical 

 and medullary substance of Corticata, but is merely due to the 

 centripetal aggi'egation of granules lying in a uniform undiffer- 

 entiated protoplasm. The cell-individual exhibits itself under 

 four phases of growth and development — (1) as a swann-spore 

 (raonadiform young or flagellula) ; (2) as an amceba form ; (3) as 

 constitufent of a Plasmodium or cell-fusion or conjugation ; (4) as a 

 cyst, which may be a flagellula(Schwarme)-producing cyst, an 

 amoebula-producing cyst, acovered-spore(chlamydospore)-producing 

 cyst (sporocyst sens, stric., Zopf), or a simple resting cyst which 

 does not exhibit any fission of its contents (hypnocyst). Any one 

 of these phases may be greatly predominant and specialized whilst 

 the others are relatively unimportant and rapidly passed through. 



Class I. PKOTEOMYXA, Lankester, 



Characters. — Gymnomyxa which exhibit in the amceba phase 

 various forms of pseudopodia often changing in the same individual, 

 and do not produce elaborate spore cysts ; hence they are not re- 

 ferable to any one of the subsequent six classes. Mostly minute 

 forms, with small inconspicuous nucleus (absent in some ?). 



A division into orders and families is not desirable, the group 

 being confessedly an assemblage of negatively characterized or 

 insufficiently known forms. 



Genera. — Vampyrella, Cienkowski (15) ; Vampyrellidium, Zopf 

 (13) ; Spirophora, Zopf ( = Amoeba radiosa, .Perty) ; Haplococcus, 

 Zopf ; Leptophrys, Hertwig and Lesser (16) ; Endyomem,a, Zopf ; 

 BursuUa, Sorokin (17) ; Myxastrum, Haeckel (1) ; Enteromyxa, 

 Cienkowski (18) ; Colpodella, Cienkowski (19) ; Fseudospora, Cien- 

 kowski (20) ; Protomo7ias, Cienkowski (15) ; Diplqphysalis, Zopf 

 (13) ; Gymnocoecus, Zopf ; Aphelidium, Zopf ; Fseudosporidium, 

 Zopf ; Protomyxa, Haeckel (1) ; Plasmodiophora, Worouin (21) ; 

 Tetramyxa, Gobel (22) ; Gloidium, Sorokin (23) ; Gymnophrys, 

 Cienkowski (24) ; Myxodictyum, Haeckel (1) ; Boderia, Wright 

 (25) ; Biomyxa, Leidy (92) ; Protogenes, Haeckel (1) ; Protamceba, 

 Haeckel (1); Nuclearia, Cienkowski (26); Monobia, Aim. Schneider 

 (27) ; Archerina, Lankester (14). 



The forms here brought together include several genera (the 



first nineteen) referred by Zopf to the Mycetozoa, some again 

 (Vampyrella, Myxastrum, Nuclearia, Monobia) which are by 

 Biitschli associated with the Heliozoa, others (Protamceba, Gloidium) 

 referred by the same authority to the Lobosa (Amcebsea) and others 

 (Colpodella, Protomonas) which might be grouped with the lower 

 Flagellata. By grouping them in the manner here adopted we 

 are enabled to characterize those higher groups more satisfactorily 

 and to give a just expression to our present Want of that knowledge 

 of the life-history both of these forms and of the higher Gymnomyxa 

 which when it is obtained may enable us to disperse this hetero- 

 geneous class of Proteomyxa. The group has the same function 

 in relation to the other classes of Gymnomyxa which the group 

 Vermes has been made to discharge in relation to the better defined 

 phyla of the Metazoa ; it is a lumber-room in which obscure, lowly- 

 developed, and insufficiently known forms may be kept until they 

 can be otherwise dealt with. 



It is true that, thanks to the researches of Continental botanists 

 (especially Cienkowski and Zopf), we know the life-history of 

 several of these organisms ; but we are none the less unable to con- 

 nect them by tangible characteristics with other Gymnomyxa. 



Nearly all of the above-named genera are parasitic rather than 

 " voracious," that is to say, they feed on the organized products of 

 larger organisms both plants and animals (Haplococcus is parasitic 

 in the muscles of the pig), into whose tissues they penetrate, and 

 do not, except in a few cases (Protomyxa, Vampyrella), engulph 

 whole organisms, such as Diatoms, &c., in their protoplasm. Many 

 live upon and among the putrefying debris of other organisms 

 {e.g., rotting vegetable stems and leaves, excrements of animals), 

 and like the Mycetozoa exert a digestive action upon the substances 

 with which they cqme in contact comparable to the putrefying and 

 fermentative activity of the Schizomycetes (Bacteria). 



Fig. II. illustrates four chief genera of Proteomyxa. 



Protomyxa aurantiaca was described by Haeckel (1), who found 

 it on shells of Spirula on the coast of the Canary Islands, in the 

 form of orange yellow flakes consisting of branching and reticular 

 protoplasm nourishing itself by the ingestion of Diatoms and 

 Peridinia. This condition is not a simple amoeba phase but a 

 "pla.smodium " formed by the union of several young amcebse. The 

 Plasmodium under certain conditions draws itself together into a 

 spherical form and secretes a clear membranous cyst around itself, 

 and then breaks up into some hundreds of flagellulse or swarm- 

 spores (Fig. II. 2). The diameter of the cyst is '12 to '2 millimetre. 

 The flagellulse subsequently escape (Fig. II. 3) and swim by the 

 vibratile movement of one end which is drawn out in the form of a 

 coarse "flagellum. The swarm-spore now passes into the amoeba 

 phase (Fig. II. 4). Several of the small amcebse creeping on the 

 surface of the spirula-shell then unite with one another and form , 

 a Plasmodium which continues to nourish itself by "voracious" 

 inception of Diatoms and other small organisms. The Plasmodia 

 may attain a diameter of one millimetre and be visible by the 

 naked eye. 



A nucleus was not observed by Haeckel in the spores nor in the 

 amoeba phase, nor scattered nuclei in the Plasmodium, but, it is -not 

 improbable that they exist and escaped detection in the living con- 

 dition, in consequence of their not being searched for by methods 

 of staining, &c., which have since come into use. A contractile 

 vacuole does not exist. 



Vampyrella spirogyrse, Cienkowski (Fig. II. 5, 6, 7), is one of 

 several species assigned to the genus Vampyrella, all of which 

 feed upon the living cells of plants. The nucleus previously stated 

 to be absent has been detected by Zopf (13). There is no con- 

 tractile vacuole. The amceba phase has an actinophryd character 

 {i.e., exhibits fine radiating pseudopodia resembling those of the 

 sun-animalcule, Actinophrys, one of the Heliozoa). This species 

 feeds exclusively upon the contents of the cells of Spirogyra, effect- 

 ing an entrance through the cell-wall (Fig. II. 5), sucking out the 

 contents, and then creeping on to the next cell. In some species 

 of Vampyrella as many as four amoeba-individuals have been 

 observed to fuse to form a small plasmodium. Cysts are formed 

 which enclose in this species a single amoeba-individual. The cyst 

 often acquires a second or third inner cyst membrane by the 

 shrinking of the protoplasmic body after the first encystment and 

 the subsequent formation of a new membrane. The encysted pro- 

 toplasm sometimes merely divides into four parts each of which 

 creeps out of the cyst as an Actinophrys-like amoeba (Fig. II. 7) ; in 

 other instances it forms a dense spore, the product of which is not 

 known. ' 



Protogenes primordialis is the name given by Haeckel to a 

 very simple form with radiating filamentous pseudopodia which 

 he observed in sea-water. ,It appears to be the same organism as 

 that described and figured by Max Schultze as Amceba porrecta. 

 Schultze's figure is copied in Fig. II. 12. No nucleus and no con- 

 tractile vacuole is observed in this form. It feeds voraciously on 

 smaller organisms. Its life-history has not been followed over even 

 a few steps. Hence we must for the present doubt altogether as to 

 its true affinities. Possibly it is only a detached portion of the 

 protoplasm of a larger nucleate Gymnomyxon, The same kipd of 



