93 



one on each side of the middle line ; they extend the 

 whole length of the body and give off numerous diverticula 

 ^caeca) short ones from their inner sides, long and branch- 

 ing ones from their outer sides. 



NOTE. For main features of Nervous and Excretory Systems 

 of the Liver-fluke, see Platyhelminthes, page 89. 



'Give an Account of the Reproductive System of the Liver- 

 fluke. 



The Liver-fluke is hermaphrodite, each individual having 

 two sets of organs (male and female). 



Male organs. There are two (tubular and branching) 

 testes, one behind the other in the central area of the body. 

 Each has a long duct, the vas deferens. The spermatozoa 

 pass by the vasa deferentia into the short vesicula seminalis 

 which is situated in front of the ventral sucker, and which 

 leads into a thin ejaculatory duct that opens into a muscular 

 cirrus or penis. The penis opens into the genital outlet. 

 The vesicula seminalis, ejaculatory duct, and penis occupy 

 a slight cavity, the cirrus sac, between the ventral sucker 

 and the genital outlet. 



When expulsion of the sperms is about to take place, 

 the penis is protruded by evagination ; the ejaculatory 

 duct is then telescoped inside the penis, and the openings 

 are correspondingly transposed. 



Female organs. On the right side, in front of the an- 

 terior testis, is the ovary ; it resembles the testis, but is 

 less extensive, and a short narrow ovarian duct issues from 

 it. Along the whole length of the body, on both sides, 

 numerous yolk-glands and their ducts form a diffuse 

 branched system opening into two transverse yolk or 

 vitellarian ducts which meet together in a small median 

 reservoir. This reservoir gives off a small median vitel- 

 larian duct which joins the ovarian duct to form the wide 

 and convoluted oviduct or uterus. The uterus narrows as 

 it nears the genital outlet where it opens beside the penis. 



The eggs are fertilised before they reach the uterus ; 

 and each egg, along with some nutrient yolk from the 

 yolk-glands, is enclosed in a tough " shell " secreted by 



