THE ROUNDWORMS OF DOMESTIC SWINE. 



29 



The spiral of the caudal end of the male appeared in a few cases as 

 a single coil like that of Arduenna strongylina. In other cases it con- 

 sisted of an irregular double twist (fig. 28). In the greater number 

 of specimens examined, however, it formed a broad open spiral like 

 a corkscrew (fig. 19). Comparing the spiral to the thread of a screw, 

 and considering the tip of the tail as the point of the screw, the spiral 

 resembles a left-handed screw with three (rarely four) threads; no 

 cases were seen in which the spiral 

 revolved in the opposite direction. 



The bursal wings are described 

 as symmetrical by Railliet and 

 Henry (191 Ib) and are so depicted 

 by Von Drasche (1884a). The right 

 wing is, however, a little longer than 

 the left wing (fig. 19). Ciurea (1912) 

 considers that it is also narrower, 

 but this statement could not be veri- 

 fied by the present writer. Ciurea 

 (1912) states that the bursal wings 

 extend throughout the twisted por- 

 tion of the tail. As seen by the 

 present writer they extend only about 

 half this distance (fig. 19). The 

 cuticle on the ventral side of the 

 male (fig. 19), commencing at some 

 distance anterior of the spiral, is 

 marked with longitudinal striations 

 intercepted by transverse lines, ap- 

 pearing under high power as longi- 

 tudinal folds of the cuticle separated 

 by transverse ridges. A similar struc- 

 ture has already been noted on the 

 ventral surface of Arduenna strongy- 

 lina (fig. 2) . As in most nematodes, 

 the papillae are arranged symmetri- 

 cally on either side of the median 

 line. Their grouping and structure 

 have already been discussed. 



The intestine is much convoluted, growing broader close to the 

 cloaca. The vesicula seminalis occupies most of the body cavity in 

 the posterior end, maintaining a fairly uniform diameter until it 

 disappears dorsal of the intestine which conceals the ductus ejacu- 

 latorius. The long convoluted testis which extends to the middle of 

 the body presents no specific characteristic features. The anus is 



I- 



mm. 



FIG. 28. Physocephalus sexalatus. General 

 view of body of male. 5. , bursa; es. , esoph- 

 agus; *p*.,spicules. X 23. (Original.) 



