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, sporocyst; 

 3a, snail of the genus Limnaea; 4, division of sporocyst; 

 5, sporocyst containing developing redise; 6, redia with cer- 

 carise or more redise 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 



