THE NEOSPORIDIA 



427 



nuclear bodies," round masses larger than the nucleus, and staining very in- 

 tensely with nuclear stains. The parasite occurs between the basal membrane 

 and the epithelium, or in the epithelial cells, or occasionally free in the lumen 

 of the caecum. Multiplication appears to take place by longitudinal fission. 

 No other stages are known. 



Gastrocystis gilruthi, Chatton (819), is a parasite of sheep and goats dis- 

 covered by Gilruth in Australia, but of common occurrence in Europe. The 

 parasite appears as a cyst, visible to the naked eye, in the mucous membrane 

 of the stomach. The cyst has an envelope formed by a single cell with a 

 large nucleus ; the envelope is concentrically striated, and bears externally a 

 fur of short, stiff, bristle-like processes, recalling the covering of Myxidium 

 lieberkuhni, Myxocystis, and Sareosporidia. The younger cysts contain a 

 plasmodium with a vast number 

 of nuclei, some of them in groups 

 of two, three, four, and so on up 

 to a large number, which are then 

 arranged in a single layer en- 

 closing a blastula-like sphere or 

 blastophore. The blastophore 

 becomes separated off from the 

 interstitial protoplasm of the 

 plasmodium, and each nucleus 

 grows out from the surface in a 

 tongue -like process to form a 

 cluster of sporozoite-like bodies 

 or germs in a manner very 

 similar to the sporulation of a 

 malarial parasite or of Porospora 

 or Aggregate. The ripe cyst is 

 full of an enormous number of 

 these germs (Fig. 179), each of 

 which is a fusiform body, about 



Fia. 178. Lymphocystis johnstonei : section 

 though one of the parasites lying in the 

 mesentery. N., The large nucleus of the 

 parasite ; chr., the ring of chromidia ; l.s., 

 lymph - space ; I., layer of lymphocytes 

 adherent to the parasite. After Woodcock 

 (824), magnified 45 diameters. 



is 



germ 

 cyst by 



10 M in length, with one end 



pointed and terminating in a 



rostrum, the other blunter. 



Near the blunt end is a 



large nucleus, and at about 



the middle of the body is a 



deeply-staining mass resembling 



a separate karyosome or a kinetonucleus. The surface of the 



clothed by a delicate pellicle. The germs are set free from the 



dehiscence. 



The affinities of Gastrocystis remain for the present quite uncertain. 

 Negre reports the occurrence of a similar cyst in the duodenum of a mouse 

 of which the faeces infected other mice with sarcosporidiosis (see p. 421), 

 and suggests that Gastrocystis may be a stage in the development of 

 Sarcosporidia. 



Pansporclla perplexa, Chatton (818), is a parasite of the intestine of Daphnia 

 spp., occurring in the form of amoeboid, bodies, reaching 80 /* in diameter, 

 adherent, but not permanently attached, to the epithelium of the intestinal 

 wall. The amoeboid movement may be active, but does not serve for food- 

 capture, since nutrition is effected by the osmotic method. The cytoplasm 

 is divided into hyaline ectoplasm and granular endoplasm containing a single 

 large nucleus in which the karyosome has the form of one or two caps adherent 

 to the nuclear membrane. The amoeboid phase does not multiply by fission, 

 but becomes encysted, and then the nucleus divides repeatedly until a large 

 number of small nuclei are present. The body then becomes divided into a 

 number of spores, each containing eight nuclei, of which six degenerate, 

 so that the ripe spore is binucleate. Germination of the spore sets free a 

 binucleate amcebula which divides, apparently, into two, each of which has 



