NO. 2131. 



NEMATODE PARASITES OF RODENTS— HALL. 



73 



sides of the tube and which are apparently developed from the ven- 

 tral line of the worm but not in the dorso-ventral line of the worm 

 as might be expected. 

 The vulva, moreover, is 

 located transversely and 

 not longitudinally. This 

 vulva is formed by a 

 deep slit in the end of 

 the tube, the slit forming 

 two prominent lips. The 

 origin of the tube is be- 

 tween a third and a 

 fourth of the length of 

 the worm from the head, 

 or 4 to 5 mm. in mature 

 specimens. The inclosing 

 vaginal tube attains a 

 maximum length of 

 about 1.9 mm. and a 

 maximum thickness of 

 225 [X. The vagina en- 

 ters this tube as a thick- 

 walled structure, but be- 

 fore attaining the distal 

 end the walls thin to a 

 membrane of epithelial 

 nature. Shortly after 

 its entrance into the 

 body cavity proper (fig. 

 83), the posteriorly di- 

 rected vagina transforms 

 into a much dilated sac, 

 apparently the recepta- 

 culum seminis, oval in 

 form, the constricted 

 posterior termination 

 connecting by a short 

 uterine tube with the 

 long uterus. Near the 

 anal region the uterus 

 terminates and divides 

 to form the oviducts 

 which extend forward 

 along the sides of the uterus and transform anteriorly into the looped 

 ovaries. The eggs are of the typical Oxyurls shape, flattened on one 

 side and measure in utero 55 to 65 [x long by about 25 [jl thick. 



Fig. 82.— Oxyueis evoluta. Female. After Smith, 1908. 



