ANIMAL PARASITES 



79 



as well as by true sporogony, thus having a life cycle with alterna- 

 tion of asexual and sexual generations. The former provides 

 for the multiplication of the parasite within the host, while it 

 is through sporogony that infection of new hosts is brought 

 about. After fertilization the oosphere forms sporoblasts which 

 may or may not be covered by a sporocyst membrane 1 , and which 

 may each become transformed into one or several sporozoites. 



Fig. 25. — Diagram of the development cycle of a Coccidian. (After Reich.) 



The chief difference between the Coccidia and the Gregarinida, 

 as typified by Monocystis, is then, the intracellular habitat of 

 the parasites and the interpolation of an asexual cycle. 



There are many species of Coccidia infesting both inverte- 

 brates and vertebrates, including man. We shall use as a type 

 Eimeria stiedce, a species which commonly infests rabbits and is 

 the cause of much mortality, particularly among the young 

 animals. Related species cause serious disease of cattle, dogs, 



