258 



ZOOLOGY 



always present an anterior set of suckers (or a single anterior 

 sucker surrounding the mouth) and a posterior set, or a single 



enlr- 



A,_ 



Fia. 200.— Mono genetic Trematodes. A, Gyrodactylus. cil. disc beai-ing hooks und pro- 

 cesses at the posterior end ; ent. intestine ; gl. unicellular glands whose ducts open on the 

 surface about the anterior end ; /ii. caudal disc of the first embryo ; h^. caudal disc of the 

 second embryo ; mo. mouth ; oosp. oosperm ; ov. ovary ; p. penis ; ph. pharynx ; te. testes, 

 B, PolyBtomuiii. en. intestine ; g. p. genital pore ; mo. mouth ; -ph. pharynx ; ov. ovary ; ie. 

 testes ; u. uterus ; v., u. d. vas deferens ; vit. vitelline glands ; viL d. vitelline ducts ; x. 

 marks the position of the genito-intestinal canal connecting the oviduct vpith the intestine. 

 (Proia i\I. Braun.) 



large posterior sucker. The arrangement already described as 

 characterising the Liver-Fluke is that which is typical in the 



