THE ROUNDWORMS OF DOMESTIC SWIXE. 



27 



FIG. 25. Physocephalussexalattu. Cross 

 section through anterior part of body. 

 bd. w., body wall; I. c. w., lateral cu- 

 ticular wings. X 280. (After Von 

 Drasche, 1884a, PL XIV, fig. 4.) 



depicted by Von Drasche (1884a). In about 20 per cent of the 

 specimens examined, however, the cuticle, from the lips to the 

 beginning of the lateral cuticular wings, 

 is inflated into two hemispherical vesicu- 

 lar wings (fig. 26). This second form is 

 not mentioned by Molin (1860b) or Von 

 Drasche (1884a), but possibly may be 

 referred to byDiesing (186 la) in the ex- 

 pression "epidermide in bullam inflata 

 tunicatum" in his description of the 

 genus PJiysocephalus. 



The pharynx of P. sexalatus is about 

 three tunes as long and twice as broad as 

 that of Arduenna strongylina, and this, 

 together with the lateral wings character- 

 istic of the genus, are the salient points in 

 distinguishing the females of the two genera. At first sight the 

 ridges of the pharynx appear to form separate rings and are so 



described by Von Linstow 

 (1879b and in liti) . By careful 

 focusing, however, it is seen 

 that these ridges form a simple 

 spiral at the anterior end of the 

 pharynx and after making four 

 or five turns split up into sepa- 

 rate rings. At the posterior 

 end of the pharynx they are 

 again joined into a simple spiral 

 (fig. 18) . The final loop of the 

 anterior spiral forms the first 

 ring of the series, and the begin- 

 ning of the posterior spiral takes 

 its origin from the lower part of 

 the last ring. The number of 

 loops to the spirals and the num- 

 ber of sep arate rings is sub j ect to 

 considerable variation. A rather 

 extreme case is seen in fig. 27. 

 Here the first spiral has five 

 loops followed by a detached 

 ring. This in turn is followed 

 by a spiral of four loops, after 

 which are two detached rings. 

 The final spiral consists of 11 

 continuous loops. In every case, however, so far as observed, the ridges 

 form both spirals and rings, commencing and ending with a spiral, and 



FIG. 26. Physocephalus sexalatus. Ventral view of body 

 offemale. a., anus; c.cut. inf., cervical cutieular infla- 

 tion; 1. c. w., lateral cuticular wings; p., vulva. X 7. 

 (Original.) 



