PHYLUM PLATYHELMINTIIES 



r 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 



past 



Fig. -jo. — A-D, development of Distomum hepaticum. 

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

 various stages of development; C, redia, containing a 

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

 caria. p. op, birth opening; etit, enteron of redia; eye, 

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

 stages in the formation of cercaria:; int, intestine of 

 cercaria; mor, morula stage in the development of 

 cercariav, ces, cesophagus; or.su, oral sucker; pap, 

 head-lobe of ciliated embryo; ///, pharynx; proc, pro- 

 cesses of redia; vcnt.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- 



