THE LIVER-FLUKE. 



43 



embryo is released. Incubation takes place in the summer, and 

 occupies from three to six weeks. The embryo is covered with 

 fine hairs — cilia — and is known as the ciliated embi-yo (fig. 10, a). 

 It is lanceolate in form, broadened in front, and provided with 

 a curious boring apparatus at the anterior end. It is necessary 

 that this embryo should meet with its first host within twenty- 

 four to thirty hours after it has hatched. Should it not do so it 

 dies. Its first host is one of the water-snails (Limnceus) that we 

 see in such abundance along the sides of streams, runnels, and 



Fig. 10. — LiFE-HIHTOIlY of DiSTOMUM HEPATICUM. 



A, Ciliated embryo. B, Sporocyst. c, Redia. d, Cercaria. 



r, Pigment spots ; pli, pharynx ; pMi), blind-gut ; c, cercarite ; m, germinal cells ; 

 oil, young redia; rf, lateral *'fins"; aii), anterior sucker of cercaria; a(ii), ventral 

 sucker ; o:, oesophagus : dt, blind-gut. (After Leuckart and Thomas.) 



dykes. If the embryo comes in contact with one of the Limnoei, 

 it bores its way into its body by means of the anterior process, 

 and then enters the respiratory cavity. The host in this country 

 is Limnceus truncatulus (fig. 173, a) ; in S. America it is L. viatm ; 

 in the Sandwich Islands, L. peregra. On arriving at the respira- 

 tory cavity of this snail the embryo encysts, and becomes con- 

 verted into a body known as the sporocyst (fig. 10, b). 



