26 



PROTOZOA 



9. Anterior end of the same more highly magnified, o, protomerite ; b, layer 

 of circular flbrillse lying below the cuticle ; c, cortical substance of the 

 deutomerite; d, medullary anbstance of the deutomerite. 10. Two 



spores of Gregarina gigantea (after Butschli), showing the very thick coat of 

 the spore. 11-15. Stages in the development of Gregarina gigantea:— 11, 

 recently escaped from the spore-coat, no nucleus ; 12, still no nucleus, 

 one vibratile and one motionless process ; 13, the two processes have 

 divided; one here drawn has developed a nucleus; 14, further growth; 

 16, the deutomerite commences to develop. 16. Cysts of Sregarina 



gigantea, from the rectum of the Lobster. The double contents are 

 believed by Ed. Van Beneden to be due not to conjugation previous to 

 encystment but to subsequent Ussion. 17, 18. Gregarina longicoUis, 



Stein, from the intestine of Blaps mortimga : — 17, cephalont phase, with a 

 long proboscis-like epimerite a, attached to the protomerite & ; 18, 

 sporont phase, the epimerite having been cast preliminarily to syzygy and 

 encystment. 19. Gregarina Manieri, Aim. Schneider, from the 



intestine of Timareha tenebrieosa, to show the network of anastomosing 

 fibres beneath the cuticle, similar to the annular flbrillse of G. gigantea 

 shown in 9. 20. Gregarina (Hoplorhynchus) ohligaeanthus, Stein, 



from the intestine of the larva of Agrion. Cephalont with spine-crowned 

 epimerite a. 21. Spores of Gregarina oligacanthus. 22, 23. Grega- 



rina (Iloplorhynchus) Dujardini, Aim. Schneider, from the mtestine of 

 Lithohimforjicatus : — 22, specimen with epimerite a, therefore a " cepha- 

 lont " ; 23, specimen losing its epimerite by rupture and becoming a 

 "sporont." 



Ordbk 2. OLIGOSPOEEA, Aim. Schn. 



Gha/raaters. — The cyst-content develops itself into a definite and 

 constant but small number of spores. 



Genus linicum. — Coeddivm,, Leuck. (in intestinal epithelium and 

 liver of Mammals, and some Invertebrates, Figs. XVII. 24 to 31). 



Order 3. POLYSPOEEA. 



Charaders. — The cyst-content develops itself into a great num- 

 ber of spores (sixty or more). 



Genus unieum. — Klossia, Aim. Schn. Three species of Klossia 

 are found in MoUusca — viz., in Helix, in Cephalopods, and in 

 Chiton. Schneider's genus, Adelea, from Lithobius, appears to 

 belong here. Kloss (49) discovered the parasite of the renal cells of 

 Helix hoi-tensis represented in Fig. XVII. 18, 19, 20, 21, and 22; 

 Schneider that of Cephalopods, Fig. XVII. 32, 33. In Chiton Dr 

 Tovey has discovered a third species with very remarkable spores, 

 which are here figured for the first time (Fig. XVII. 12). 



The Drepanidium Sanarum (Fig. XVII. 45, 46, 47), discovered 

 by Lankester (50) in the Frog's blood, is probably the falciform young 

 of a Coccidium parasitic in the Frog's kidney, and discovered there 

 by Lieberkiihn (51). A spore of this Coccidium is shown in Fig. 

 XVII. 48 ; whilst in 46 two Drepanidia which have penetrated a 

 red-blood corpuscle of the Frog are represented. 



The Polysporous Coccidiidea come very close to the Gregarinide 

 genus Monocystis, from which they may be considered as being 

 derived by an arrest of development. The spores and falciform 

 young of the Coccidiidea are closely similar to those of Monocystis, 

 and the young in both cases penetrate the tissue-cells of their host ; 

 but in Monocystis this is only a temporary condition, and growth 

 leads to the cessation of such "cell-parasitism." On the other 

 hand, growth is arrested in the Coccidiidea,- and the organism is 

 permanently a ceU-parasite. 



Since the parasitism is more developed in the case of a cell-para- 

 site than in the case of a parasite which wanders in the body cavity, 

 it seems probable that the Coccidiidea have been derived from the 

 Gregarinidea rather than that the reverse process has taken place. 



Sub-class III. Myxosporidia, Biitschli. 



Characters. — Sporozoa in which the euglena-phase is a large 

 multinucleate amoeba-like organism (Fig. XVII. 34). The cysts 

 are imperfectly known, but appear to be simple ; some attain a 

 diameter of two lines. The spores are highly characteristic, having 

 each a thick coat which is usually provided with a bifurcate process 

 or may have thread capsules (like nematocysts) in its substance 

 (Fig. XVII. 40, 41, 42, 43, 44). 



'The spores contain a single nucleus, and are not known to produce 

 falciform young, but in one case have been seen to liberate an 

 amoebula. The further development is unknown. The Myxo- 

 sporidia are parasitic beneath the epidermis of the gills and fins, and 

 in the gall-bladder and urinary bladder of Fishes, both freshwater 

 and marine. 



Genera. — Myaadium, Biitschli (Pike, Fig. XVII. 34); Myxdboliis, 

 Biitschli (Cyprinoids) ; Idthoaystis, Giard (the Lamellibranch Echino- 

 cardium). 



The Myxosporidia are very imperfectly known. They present 

 very close affinities to the Mycetozoa, and are to be regarded as a 

 connecting link between the lower Gyninomyxa and the typical 

 Sporozoa. Possibly their large multinucleate amoeba phase is a 

 Plasmodium formed by fusion of amcebulae set free from spores, 

 though it is possible that the many nuclei are the result of a division 

 of an original single nucleus, preparatory to sporulation. 



Their spores are more elaborate in structure than those of any 

 other Protozoa, and are more nearly paralleled by those of some 

 species of Monocystis than by those of Mycetozoa. The thread- 

 capsules of the spores are identical in structure with those of 

 Hydrozoa, and probably serve as organs of attachment, as do the 

 furcate processes of the spore-case. It is not certain that a definite 



cyst is always or ever formed, but as occurs rarely in some Gregari- 

 nidea, the spores may be formed in a non encysted amoeba form. 



Although pseudopodia, sometimes short and thread-like, have been 

 observed in the amoeba phase, yet it is also stated that a distinction 

 of cortical and medullary substance obtains. 



The " psorosperms " of J. MuUer are the spores of Myxosporidia. 



Sub-class IV. Saroooystidia, Biitschli. 



(This division is formed by Biitschli for the reception of Sarco- 

 cystis, parasitic in the muscular fibres of Mammals, and of Amoebi- 

 dium, parasitic in Crustacea. Both are very insufficiently known, 

 but have the form of tubular protoplasmic bodies in which numer- 

 ous ovoid spores are formed from which falciform young escape. ) 



Genera. — Sarmeystis, Lankester ; Amabidium, Cienkowski (52). 

 Saroocystis(Fig. XVII. 50, 51, S. Miescheri, Lank.), was first observed 

 by Miescher in the striated muscle-fibres of the Mouse ; then by 

 Eainey in a similar position in the Pig, and taken by him for the 

 youngest stage in the development of the cysts of Tsenia solittm ; 

 subsequently studied by Beale and others in connexion with the 

 cattle-plague epidemic, and erroneously supposed to have a causal 

 connexion with that disease. It is common in healthy butcher's 

 meat. See Leuckart (47). 



Further remarks on the Sporozoa. — The Sporozoa contrast 

 strongly with the large classes of Gymnomyxa, the Heliozoa, 

 Reticularia, and Eadiolaria, as also with the Ciliate and Tentaculi- 

 ferous Corticata, by their abundant and rapidly recurrent forma- 

 tion of spores, and agree in this respect with some Proteomyxa, 

 with Mycetozoa, and some Flagellata. Their spores are remark- 

 able for the firm, chitin-like spore-coat and its varied shapes, 

 contrasting with the cellulose spherical spore-coat of Mycetozoa 

 and with the naked spores of Kadiolaria and Flagellata. 



The protoplasm of the more highly developed forms (Gregarini- 

 dea) in the euglenoid phase exhibits considerable differentiation. 

 Externally a distinct cuticle may be present, marked by parallel 

 rugfe {Monocystis serpulse) or by fine tubercles (Monocystis sipun- 

 culi). A circlet of hooks may be formed by the cuticle at one end 

 of the body. Below the cuticle is sometimes developed a layer of 

 fibrils running transversely to the long axis of the body (Fig. 

 XIX. 9 and 19), which have been regarded as contractile, but are 

 probably cuticular. The cortical layer of protoplasm below these 

 outicular structures is dense and refringent and sometimes fibril- 

 lated (Monocystis pelludda, Fig. XVII. 15). It is the contractile 

 substance of the organism, and encloses the finely granular more 

 liquid medullary substance. The grannies of the latter have been 

 shown by Biitschli (9) to give a starch-like reaction with iodine, 

 &c. Probably the protoplasm in which they lie is finely reticulate 

 or vacuolar, and when the granules are few it is actually seen to be 

 so. No contractile vacuole is ever present. In Myxosporidia the 

 medullary protoplasm is coloured yellow by hsematoidin derived 

 from the blood of its host or by absorbed bile-pigment, and also 

 contains small crystals. 



The nucleus of the Gregarinidea is a large clear capsule, with a 

 few or no nucleolar granules. It has never been seen in a state 

 of division, and it is not known what becomes of it during sporula- 

 tion, though sporulating Gregarinidea have been observed with 

 many minute nuclei scattered in their protoplasm, presumably 

 formed by a breaking up of the single nucleus. 



The habit of attaching themselves in pairs which is common in 

 Gregarinidea is perhaps a reminiscence of a more extensive forma- 

 tion of aggregation plasmodia (compare Mycetozoa). The term 

 "syzygium" is applied to such a conjunction of two Gregarinidea ; 

 it is not accompanied by fusion of substance. The formation of 

 cysts is not connected with this pairing, since the latter occurs in 

 young individuals long before encystment. Also cysts are formed 

 by single Gregarinidea, as is always the case in the non-motile 

 Coccidiidea. 



The encystment always leads to the formation of spores, but in 

 rare cases sporulation has been observed in unencysted Gregarini- 

 dea, and it occurs perhaps normally without true cyst-formation in 

 the Myxosporidia. 



The cell-parasitism of the young Sporozoa, and their flagellula- 

 like (falciform) young and active vibratile movement, are points 

 indicating affinity with the lower Gymnomyxa, and especially with 

 those Proteomyxa, such as Vampyrella and Plasmodiophora, which 

 are cell-parasites. Indeed it is probable that we have in this fact 

 of cell-parasitism, and especially of parasitism in animal cells, a 

 basis for the theoretical association of several unicellular organisms. 

 The Haplococcus of Zopf (regarded by him as a Mycetozoon) is 

 parasitic in the muscular cells of the Pig, and is probably related 

 to Sarcocystis. Eecently Von Lendenfeld (53) has described in 

 Australia an amoeba-like organism as parasitic in the skin of Sheep, 

 which will probably be found to be either a Sporozoon or referable 

 to those parasitic spore-producing Proteomyxa which are separated 

 from Sporozoa only by their negative characters (see previous 

 remarks on the negative characters of Proteomyxa). 



The application of the name "Gregarines" has sometimes been 



