THE LIVER FLUKE 



little more than a sack (sporosac), in which, by a process of 



internal budding, a number of new individuals, rediae, are pro- 



duced. These are slightly more 



highly organized, but continue 



the process of internal budding 



for several generations. Then 



the rediae, by a similar process, 



develop a new type of individ- 



uals called cercariae. These are 



again a little more complex. 



They have two suckers, a forked 



intestine and a tail. The cer- 



cariae leave the snail and be- 



come encysted on the grass. 



If now they happen to be in- 



gested by a sheep with the grass 



they are set free from the cyst 



in the stomach of the iiost. 



The parasite may now be called 



a young fluke, for if it succeeds 



in finding the opening of the 



bile duct it works its way up 



into the liver and then develops 



directly into the fluke. The 



mature fluke is well organized 



as far as digestive tract and 



reproduction Systems are COn- 



cerned. The reproductive sys- 



_ 



FIG. 231. The liver fluke, Fasaola 

 hepatica, showing the arrangement of 



tern especially is very highly cirrus sac ; 0, mouth; Ov, oviduct, or 



, . uterus; S, ventral sucker; Sg, shell 



developed. gland; T, testis; U, intestine; 7, 



755. AcommonCestodeisthe ^^ } duct - (From Tyson .after 

 tapeworm. The one common 



in the dog may be taken as a type. The eggs originate in the 

 intestine of the dog and reach the earth with the faeces. Either 



