DISTOMUM. 



143 



Distomum is a type of the Digenous Trematoda, or those 

 with two or more generations in their h'fe-cycle, which 

 alternate in their environment between two hosts, as in 



Fig. 76. — A Cercaria. 



Notice tail, suckers, bilobed 

 intestine and dotted cysto- 

 genous cells. 



Fig. 77.— Cercaria and 

 Distomum. 





Encysted Cercaria. 



(The structure can still be seen 

 through the cyst.) 



Young Distomuvt. 



Distomum. It also illustrates several adaptations, due to 

 a Somalia endoparasitic habit (see Chapter IX.). The high 

 fecundity, the complex sexual organs, and the absence of 

 sense-organs should be here noted. 



