Flatworms and Roundworms 375 



Proboscis (extruded) 



Nerve-ganglion 



Eerg,. 



Yolk-cella 



„ Intestine 



- Germ-cellfi 



Cercaria 



Ventral sucker 

 Nephridium 



Germ-cells 



Fig. 181. — Diagrams to show the life cycle of the liver fluke (Fasciola hepatica). 

 A, Egg in a case; B, miracidium (ciliated larva); C, sporocyst; D, redia (early 

 stage) ; E, redia (later stage containing cercaria) ; F, cercaria with motile tail; 

 G, cercaria (encysted and without tail) ; H, adult fluke in the liver of the sheep, 

 where it produces, perhaps, 500,000 eggs when sexually mature. Only digestive 

 and excretory systems are shown in this adult. (Consult Fig. 180, D for reproduc- 

 tive system.) (From Hegner: College Zoology. By permission of The Macmillan 

 Company, publishers.) 



