162 



PARASITES OF THE DOMESTIC ANIMALS 



the size of an ordinary pin-head. An encysted cercaria will remain alive 

 for an extended period as long as the grass upon which it is lodged is 



Fig. 88.^ — Life history of liver fluke: 1, egg containing de- 

 veloping embryo; 2, free swimming miracidium; 3, sporooyst; 

 3a, snail of the genus Limnsea; 4, division of sporooyst; 

 5, sporooyst containing developing rediae; 6, redia with cer- 

 cariae or more rediae developing within it ; 7, cercaria ; 8, young 

 fluke (after Thomson, from Thomas). 



supplied with moisture. Drought probably destroys it, though^ the 

 length of time it may survive such conditions is undetermined. ^ 

 When plants bearing these cysts are eaten by grazing animals -the 



