SPOROZOA: GREGARINIDA. 859 



Gregarines in which they best developed are the most inert. The septa 

 of the Polycystidea are constituted by exoplasm or sarcocyte. Move- 

 ments in the endoplasm are never propagated through them. The 

 granules of the endoplasm sometimes display molecular movements ; 

 they are variable in size and shape ; and in some instances either contain 

 or consist of an amyloid substance. Colouration is rare, and appears to 

 be due to the intestinal secretions of the host. Contractile vacuoles are 

 absent ; non-contractile are seen in Conorhynchus Echiuri, The nucleus 

 is single ; it is large when full grown, vesicular, with chromatin globules or 

 ribbons. It lies in the endoplasm, with the movements of which it shifts, 

 and in the Polycystidea always in the deuteromerite, into which it migrates 

 from the epimerite before the septa are complete. 



The Coccidiidae encyst as soon as they have attained their definitive 

 size. The cyst has rarely a single, but usually a double wall, is very 

 resistent, and has in Eimeria and Coccidium a micropyle. The contained 

 protoplasm gives origin to a single spore (Monosporea), to two or four 

 (Oligosporea), or to a large number (Polysporea}. The spore is naked in 

 Orthospora, Eimeria and Gymnospora, in other instances with a spore- 

 membrane which may be double. The spore-protoplasm gives origin to a 

 single elongate falciform body in Coccidium oviforme of the Rabbit, to 2 

 in some species of Klossia, to 2-4 in Cyclospora, to 4 in Orthospora, to 

 many in Eimeria, &c. In the last-named genus they are formed on one 

 aspect only of the spore. A small quantity of protoplasm, the ' nucleus de 

 reliquat,' may remain after the formation of the falciform bodies. The 

 division of the nucleus in the formation of spores and falciform bodies has 

 been observed in some instances. The falciform body may move while 

 still within the spore case, more energetically after its escape. It does so 

 either by bending into a semicircle, by gliding, rotating round a point, or 

 by feeble amoeboid motions (Eimeria falciformis]. It probably enters a 

 cell whilst in the falciform condition. The cycle of development is usually 

 completed in a single host ; in some instances in its faeces, as in Cocci- 

 dium oviforme, the intestinal Coccidia of the Rabbit and birds and in 

 Cyclospora from Glomeris 1 . 



As to other Gregarinida. The Monocystids of the Earthworm quit 

 the sperm-blastophores in which they live ; the Polycystids lose the 

 epimerite wholly or in part, e.g. in Clepsidrina, or its retinacular pro- 

 cesses are alone absorbed (Echinocephalus}. A conjugation so-called may 

 take place ; the two anterior extremities come into contact (apposition), as 



1 A parasite, Drepanidium Ranarum, inhabits the red blood-corpuscles of the Frog, and has a 

 close structural resemblance to a falciform body, and is perhaps derived from a Coccidium infesting 

 the intestinal and renal epithelia. It has been observed to quit one corpuscle and enter another. 

 Other Gregariniform parasites have been found in the blood of Emys lutaria, Lacerta viridis, and 

 several birds. See Ray Lankester, Q. J. M. xxii. 1882 ; Danilewski, A. M. A. xxiv. 1885 ; Id. Biol. 

 Centrablatt. v. 1885-6, and Archives Slaves de Biologic, i. 1886. 



