INTRODUCTION. 7 



is described as an intermediate host, and the latter, in which 

 the sexual process is perfected, as the final or definitive host. 



Life-history. — The hfe-histories of different groups vary 

 a good deal, but there is always some resemblance to a common 

 fundamental type. The hfe-history of the Coccidium Eimeria 

 stiedse (Lindem.) (fig. 1), occurring in the liver and intestine 



Fig. 1.— Life-cycle of a tjrpical coccidium, Eimeria stiedse (Lindem.). 

 1-5, sporogony; 6-15, schizogony; 17-20, gametogenesis ; 

 21-23, fertilization. (After Reich). 



of the rabbit, may be described as typical. The sporozoite (6) 

 escapes from the spore in the intestine of the host, and, gKding 

 like a minute Gregarine, bores its way into the epithehal 

 cell (7) and becomes a trophozoite (8). The latter feeds at 

 the expense of the cytoplasm of the host -cell and grows into 



