ECTOPARASITIC TKEMATODES. 289 



The ovary is an irregularly U-shaped body lying at the 

 front end of the middle third of the body ; but the two arms of 

 the U are so close to each other that the ovary appears round- 

 ish in surface view. The oviduct starts from the anterior end 

 of the left arm of the U, and after proceeding for a short dis- 

 tance forwards receives the openings of the shell glands and 

 becomes the ootyp. This is very spacious and is the direct 

 continuation of the oviduct ; its anterior end nearly reaches the 

 anterior intestinal arc, just behind which begins the uterus. 

 The latter is a rather slender duct proceeding directly towards 

 the left side of the body and opening into the genital atrium side 

 by side with the seminal vesicle. The shell glands are very 

 numerous and large, and their long necks are very prominent 

 even in surface view. The vitellarium is very extensive and 

 occupies more than the middle two-fourths of the body ; it is 

 present not only in the lateral portions but also in the median 

 portion enclosed by the main intestinal branches, where the lobes 

 closely intermingle with one another. Each paired yolk duct is 

 formed by the ynion of two ducts coming from the anterior and 

 posterior portions, arising just in front of the ovary. The single 

 yolk duct is exceedingly short and opens directly into the oviduct 

 at about the middle of its length. 



There are two roundish testes, nearly equal in size, in the 

 median line of the body, one lying at some distance in front of 

 the other, behind the ovary. The vas efiferens of the anterior 

 testis starts from its hind end and curves towards its left side, 

 where it joins the duct coming from the posterior testis, which 

 gives it off from its front end. The vas deferens proceeds for- 

 ward on the left side of the anterior testis and the ovary, and 

 passing on the dorsal side of the paired yolk duct of the left 



