BY S. J. JOHNSTON. 311 



Alimenfari/ canal. — The oral sucker opens behind into a 

 pre-pharynx (Fig. 43), nearly equal in length to the pharynx, 

 which is a subglobular thick- walled structure, 01 40 mm. wide. 

 There is a moderately long oesophagus, about equal in length 

 to the pharynx and prepharynx taken together (Fig. 43) ; the 

 intestinal limbs run back to the posterior end of the body. 

 The excretory vesicle (Fig. 6) is Y-shaped, with a very long 

 stem that divides into two short limbs just behind the ootype 

 and related parts. From these limbs, a pair of moderately 

 fine, anterior, collecting ducts run forwards in a lateral posi- 

 tion, as far as the base of the oral sucker. About the level 

 of the ventral sucker, or just behind it, a pair of posterior 

 collecting ducts, much finer than the anterior ducts, arise 

 from these, and run back to the posterior end of the body. 

 Taking their origin from these collecting tubes, a large num- 

 ber of capillary tubes form a loose network all over the 

 surface of the body (Fig. 6) : short branches, arising from the 

 network at intervals, end in excretory cells. The number 

 seems to vary a little in different individuals, but there are 

 about 160 of these cells. 



The testes lie in the middle line, one behind the other, in 

 the middle of the posterior half of the body. They are large, 

 compact, spherical bodies, nearly as large as the oral sucker, 

 0-214 mm. in diameter. The vasa deferentia run forwards, 

 and do not join till they reach the base of the vesicula 

 seminalis, which lies partly behind, and partly alongside the 

 ventral suckei'. The cirrus-sac is a very elongated, S-.shaped 

 structure, 0-611 mm. long (not following the bends, but 

 measured in a straight line from its posterior to its anterior 

 extremity), beginning behind, and to the right of the ventral 

 sucker. In a graceful curve, it bends forwards and inwards 

 to a position in front of the vertral sucker, and to the left of 

 the middle line, whence, by a sharper bend, it runs forwards 

 and to the right, to reach the genital pore, which lies just 

 behind the intestinal fork and a little to the right of the 

 middle line (Fig. 47). 

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