324 



ANIMAL BIOLOGY. 



[Part 1 1. 



(5) Cercaria, which pass out of the intermediate host and become 



(6) Encysted on blades of grass, which are eaten by sheep. The cyst 

 dissolves, and the young flukes pass into the liver of their host, each 

 developing there into an adult hermaphrodite 



(7) Fasciola hepatica. 



The Distoma Stage. The liver-fluke, which is the terminal 

 product of this long series of changes, is somewhat oval in form, 



D. 



FIG. 95. LIVER-FLUKE : DIGESTIVE SYSTEM. 

 (After A. P. Thomas and La Valette.) 



A. Young distoma ( X 70). cli. Branched digestive canal, ex. sy. Excretory 

 system. m.cZ. Its mid duct. n. Nerve, n. g. Nerve ganglion, o. s. Oral 

 sucker, p. s. Posterior sucker, ph. Pharynx. 



B. C. D. Stages in the growth of distoma ( x 7) to show relative positions 

 of suckers. 



and is provided with two suckers. In Fig. 95, B., G., and D., 

 three stages of growth (after A. P. Thomas x 7 J) are shown. The 



