44 



INVERTEBRATE ZOOLOGY 



these only the latter bears a nucleus. Frequently, especially in 

 the young stages, there is an outgrowth of the protomerite carry- 

 ing various structures for attachment to the host. This is termed 

 the epimerite. Since no mouth opening is present, all food is 

 absorbed directly through the body wall. A myoneme layer 

 within the deeper region of the ectoplasm renders body move- 

 ments possible. 



Fig. 28. ■ — Life cycle of Eimeria schubergi. Stage V to VIII, a period of 

 schizogony; XIo and Xlla beginning of development of male and female gam- 

 etes in sporogony period of the cycle. {From Shall, La Rue, and Ruthven). 



The Eugregarinaria are the typical gregarines which in their 

 life cycle involve only a propagative phase. This suborder is 

 usually subdivided into two groups, the cephaline gregarines 

 which bear an epimerite at least in the early developmental 

 stages, and the acephaline gregarines which never possess an 

 epimerite. The cephaline gregarines, of which there are numer- 

 ous genera and species, occur chiefly in the alimentary canal of 

 arthropods. Gregarina, Stenophora, and Leidyana are a few of 

 the numerous genera. The acephaline gregarines are chiefly 

 coelom parasites, either lying free in the coelom or sometimes 



