1 88 Introduction to A nimal Morphology. 



organs (lemnisci), which lie directly behind the pro- 

 boscis, each of which has a central large vessel giving 

 off many close branches. Although these vessels do 

 not open outwards, yet they probably form a water- 

 vascular system ; the smaller vessels of the lemniscus 

 and those of the body wall do not anastomose. From 

 the base of the proboscis a central connective band is 

 continued backwards, which supports the sexual 

 organs (ligamentum suspensorium ; Lespcs describes 

 a rudimental intestine and gland attached to this). 

 The males are smaller, and have a hinder sucker used 

 in copulation, in the middle of which is the protrusible 

 penis, with two retractor muscles at its base. They 

 have also 2-}, testes whose ducts opens into a common 

 vas deferens, dilated into several vesiculae seminales. 

 The females have an ovary, which may fill the whole 

 body, often divided longitudinally, and emitting the 

 ova by dehiscence. A bell-shaped uterine funnel re- 

 ceives these, and they pass out by a short vagina at 

 the posterior end of the body. The fusiform eggs 

 have no germinal vesicle, and the embryo forms peri- 

 phericallyinthem. The eggs are eaten by Amphipods, 

 Isopods, &c., and their embryos appear as hook- 

 armed gregariniform worms.* These burrow out of 

 the intestine, lose their hooks, become encysted, and 

 are eaten in this stage by fish, water-fowl, &c., in 

 which they finally develop. The musculo-vascular 

 layers develop from the outer embryonic lamina, 

 within which the nerves, proboscis, and genitals arise. 



Echinorhynchus is unsegmented. E. gigas inhabits the 

 intestines of Swine, and was once found in Man {Lambl) ; E. 



* The embryo of E. claviceps has no hooks at first. 



