134 



MANUAL OF ZOOLOGY 



SECT. 



head-lobe (pap.}- There is no vestige of internal organs, with 

 the exception of a pair of flame-cells. The ciliated larva swims 

 about in water, or moves over damp herbage for a time, and 



FIG. 65. A D, development of Distomum hepaticum. 

 A, ciliated larva; B, sporocyst, containing rediae in 

 various stages of development ; C, rcdia, containing a 

 daughter redia, and cercariae ; D, fully developed cer- 

 caria. b. op. birth opening ; ent. enteron of redia ; eye, 

 eye-spots ; gast. gastrula stage of redia ; germ, early 

 stages in the formation of cercariae ; int. intestine of 

 cercaria ; mor. morula stage in the development of 

 cercariae ; ccs. oesophagus ; or. su. oral sucker ; pap. 

 head-lobe of ciliated embryo ; ph. pharynx ; proc. pro- 

 cesses of redia ; vent.su. ventral (posterior) sucker. 

 (After Thomas.) 



perishes unless it happens to reach a Pond-snail (Limn<za\ 

 as a parasite of which it is alone able to enter into the next 

 phase of its life-history. When it meets with the Snail, 



