BIOLOGY AND HUMAN WELFARE 



397 



Proboscis (extruded) 



Nerve-ganglion 



..Intestine 



-Germ-cells 



Cercaria 



Ventral Backer 



Nephridium 



Germ-cells 



Fig. 251. — Life history of the Liver Fluke, Fasciola hepatica. A, 'egg'; 

 B, miracidium; C, sporocyst; D, E, rediae; F, cercaria; G, encysted stage; 

 H, adult (nervous and reproductive systems omitted). (From Hegner, after 

 Kerr.) 



