34 



SYSTEMATIC ZOOLOGY 



into two regions, a smaller anterior, and a larger posterior, — the 

 latter contains the nucleus. Cysts are formed as in Monocys- 

 tis, and within, a number of spindle-shaped bodies called pseudo- 

 navicellae are formed ; but a part of the contents of the cyst 

 always remains undivided and is known as the residual body. 

 The contents of each pseudonavicella then divides into from 

 two to eight crescentic spores, with a residual body as before, 





12 3 4 s 6 



FlG. 15. Various Sporozoa. i, Porospora (Gregarina) gigantea, from the 

 intestine oi the lobster; 2, Actinocephalus oligacanthus, young individual 

 with hooks ; 3, Eimeria falci/ormis, in an epithelial cell of the intestine of the 

 mouse; 4, Myxidium lieberkuhnii, amoeboid, from the urinary bladder of 

 the pike ; 5, Sarcocystis , in a muscle of the pig ; 6, Plasmodium, the malarial 

 parasite; successive stages of development (1-5, after Biitschli ; 6, chiefly 

 after Grassi.) 



and each spore becomes a new individual. The adults live in 

 the intestinal canal and are capable of slow locomotion by 

 means of a general contraction of the bodv ; the young embed 

 themselves within the cells which line the intestine, and only 

 when mature do they come out into the canal, often remaining 

 for some time in connection with the cells by means of an organ 

 of attachment frequently provided with hooks (Fig. 15, 1 and 2). 



