Chap. XVII.] THE LIVER-FLUKE AND TAPE-WORM. 325 



relative shifting of the suckers should be noted. The anterior 

 or oral sucker (o. s.) is at the anterior end of the body, and in 

 this the mouth occupies a central position. The other (p. s.) is 

 ventral, and relatively nearer the posterior end in young flukes 

 than in the adult organism. The cuticle has minute spines. 



The mouth leads into a muscular pharynx (Fig. 95, A., pli.\ 

 which is followed by a short oesophagus. The alimentary canal 

 then bifurcates, one limb passing down either side of the body and 

 ending blindly. Each limb has a number of lateral branches. In 

 Fig. 95, A. (partly after A. P. Thomas x 70), these are repre- 

 sented at an early stage, viz., that shown in B. In later stages 

 the branches are more complicated, though they always end 

 somewhat bluntly, and the digestive organs are masked by the 

 organs of reproduction. There is no anus. Living, as does the 

 fluke, upon the prepared juices of its host, there is presumably 

 little indigestible matter in its stolen food-stuff. 



Excretory System. At the posterior end of the body there is an 

 excretory pore which leads into a median tube (Fig. 95, m. d.). 

 From this tube are given off a number of ducts which branch 

 repeatedly, and form a net- work (ex. sy.). The fine terminal 

 vessels end in minute ciliated funnels, opening into the lacunar 

 spaces which represent the ccelom. 



Nervous System. This consists of a nerve-ring round the 

 pharynx, with a single ventral and paired lateral ganglia (n. g.). 

 From the lateral ganglia arise lateral nerves (n.), running down 

 the sides of the body. 



The Generative System. The liver-fluke is hermaphrodite, 

 male and female organs being developed in each individual. It 

 would seem, however, that there is cross-fertilisation, so that the 

 ova of one individual are fertilised by the spermatozoa of another. 



The testes (spermaries) are large branched and multi-lobed organs 

 occupying much of the central part of the body (Fig. 96, ts.). 

 Two vasa deferentia (v. d.) pass forward and unite into a reser- 

 voir and looped duct (ductus ejaculatorius), which terminates in 



