30 THE ROUNDWORMS OF DOMESTIC SWINE. 



circular, like that of Arduenna strongylina, but not surrounded by a 

 serrated ring. 



I The vulva (35 ft in diameter), as in Arduenna strongylina, appar- 

 ently occupies a somewhat lateral rather than ventral position, open- 

 ing toward the right side (fig. 22). It is situated just below the 

 middle of the body, dividing the worm in the ratio of 9 to 8. Accord- 

 ing to Ciurea (1912) the cuticle in the region of the vulva is marked 

 with longitudinal thickenings which may interlock with the cuticular 

 ridges on the ventral surface of the male, and thus assist in maintain- 

 ing the position of the male in copulation. The vagina, extending 

 posteriorly along the right side, is at first 50 ft in diameter, but gradu- 

 ally broadens to 105 ft at its posterior end, where it disappears from 

 the ventral side, extending dorsal of a lobe of the uterus. The dis- 

 tance from the vulva to this point is 976 /*. The wall of the vagina 

 is relatively thick, composed of transverse muscle fibers. The lumen 

 is 20 // in diameter. Eggs containing well-developed embryos 

 ready to pass out could be seen in single file in the lumen of the 

 vagina near the opening (fig. 22). Railliet and Henry (191 Ib) 

 describe the vulva as opening posteriorly at the limit of the third 

 and four fifths of the body. Von Linstow (in litt) places it somewhat 

 posterior of the middle of the body, dividing the worm in the ratio 

 of 10 to 9. 



The arrangement of the uteri and ovaries in the body of the female 

 is, so far as could be seen, similar to that of Arduenna strongylina. 

 The convoluted ovary of the posterior uterus occupies the caudal 

 extremity of the worm, its terminus disappearing dorsal of the pos- 

 terior uterus. A loop of the anterior uterus extends nearly to the 

 caudal end. The exact length of the vagina was not determined. 

 A loop of the posterior uterus, corresponding to the loop of the anterior 

 uterus, lies underneath the anterior uterus and extends nearly to its 

 terminus. The union of the vagina with the uteri was not seen, nor 

 was the anterior ovary traced throughout its length. While neither 

 uterus was followed throughout its entire length, the two termini, 

 one posterior the other anterior, the posterior uterine loop, and the 

 anterior loop, are all similar to the arrangement seen more clearly in 

 Arduenna strongylina. 



Ciurea (1912) depicts a pluglike protuberance at one of the poles 

 of the eggs of Physocephalus sexalatus, which bears a superficial re- 

 semblance to the operculum of a Trichuris egg, but does not penetrate 

 the eggshell as in the latter case. This feature was not seen by the 

 present writer; however, a faint transverse line could be seen at 

 either pole (fig. 23), which apparently is the line of fissure along which 

 the shell breaks when the embryo is liberated. 



