130 KANSAS UNIVERSITY SCIENCE BULLETIN. 



extend to the posterior end of the middle third of the body, 

 almost to the testes. They are very thin-walled tubes, with 

 many shallow outpouchings. They are about the same diam- 

 eter at all points, except at the very end, where there is a 

 slight enlargement The average diameter is .064 millimeter. 



The excretory vesicle is a Y-shaped, very voluminous organ. 

 Beginning with a very small pore at the posterior end of the 

 body, the vesicle extends anteriorly, suddenly becoming much 

 larger and filling the greater part of the body cavity for a 

 short distance. It becomes narrow to pass between the testes, 

 but widens again, and soon bifurcates, each branch passing 

 forward just within the intestinal caeca, and, gradually grow- 

 ing smaller, ends near the bifurcation of the intestinal caeca. 

 The course is dorsal to all other organs, through the very tips 

 of the crura pass partially ventral to the intestinal caeca. The 

 walls are very thin, and, except a short distance at the pos- 

 terior end, can be traced only in sections. 



The testes are two partially lobate bodies, situated just pos- 

 terior to the middle third of the body in the same transverse 

 plane. They differ somewhat in shape, but they are approx- 

 imately the same size. The shape is variable in different in- 

 dividuals. The average size is .144 millimeter in length and 

 .126 millimeter in width. The vasa efferentia pass from the 

 anterior end forward and join the vesicula seminalis sepa- 

 rately. The last-named organ, together with the pars pros- 

 tatica and cirrus, are enclosed in the long cirrus-sac, which 

 begins just to the left of the median line anterior to the ace- 

 tabulum and passes in a curving course to the genital pore on 

 the left ventral surface, near the oral sucker. The cirrus-sac 

 is .456 millimeter in length and .052 millimeter in diameter at 

 the largest point. The vesicula seminalis bends on itself in 

 the posterior end of the cirrus-sac. It is followed by a very 

 short pars prostatica, which in turn is followed by the cirrus. 

 The cirrus is small and weak. 



The ovary is situated just posterior to the middle of the 

 body and to the right of the median line. It is nearly 

 spherical, measuring .105 millimeter long and .098 millimeter 

 in diameter. Slightly dorsal and to the left is the shell gland 

 surrounding the small ootype. The short oviduct joins the 

 ootype on the anterior and the yolk duct on the posterior side. 

 From the ventral side of the ootype the uterus proceeds pos- 



