PHYLUM PLATYHELMINTHES 



J 35 



most part, the enteric canal, the liver, or the lungs of some 

 animal of the Vertebrate or back-boned class (fishes, amphib- 

 ians, reptiles, birds, or mammals), swallowing the digested 



eye 



FIG. 70. A-D, development of Distomum hepaticum. 

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

 various stages of development; C, redia, containing a 

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

 caria. b.op^ birth opening; etit, enterqn of redia; eye, 

 eye-spots; gist, gastrula stage of redia; germ, early 

 stages in the formation of cercariae; int, intestine of 

 cercaria; mor, morula stage in the development of 

 cercariae; ces, 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.) 



food or various secretions of their host. Others are external 

 parasites, living on some part of the outer surface of their 

 host, and feeding on mucus or other secretions of the- in- 



