THE EOUNDWORMS OF DOMESTIC SWINE. 31 



COMPARISON OF PHYSOCEPHALUS SEXALATUS AND ARDUENNA 



STRONGYLINA. 



The following comparison of appearances of Arduenna strongylina 

 and Physocephalus sexalatus will assist in separating the two species 

 without the aid of a magnifier. 



Males. Tail of Physocephalus sexalatus ending in a spiral, Ardu- 

 enna strongylina ending in a single coil; PJiysocephalus sexalatus 

 shorter and slenderer than Arduenna strongylina. 



Females. PJiysocephalus sexalatus straight, or nearly so; speci- 

 mens preserved in alcohol when lifted out of a petri dish with a 

 needle bend sharply in the middle. Body slenderer than Arduenna 

 strongylina, except toward the posterior end, which is thicker and 

 blunter. 



Alcohol specimens of Arduenna strongylina are usually curved in a 

 half circle. They are thicker in the middle of the body than Physo- 

 cephalus sexalatus and pointed at both ends. On being lifted with a 

 needle they do not collapse like PJiysocephalus sexalatus, but maintain 

 their crescentic shape. 



As has already been stated, Molin (1860b) was the first to distin- 

 guish this species from Arduenna strongylina, with which it had been 

 confused by Diesing (185 la). Besides the specimens from the white- 

 lipped peccary, Molin (1860b) also found two females of this species 

 in a bottle containing specimens of Arduenna strongylina collected 

 by Bremser from the stomach of the wild boar and deposited in the 

 Vienna Museum. That it has only twice been reported in Europe 

 in association with Arduenna strongylina is perhaps due to confusion 

 of the two species, an error which appears to have occurred in at least 

 one case (Von Linstow, 1879b). In the United States it has been 

 found in nearly every case in which specimens of Arduenna strongylina 

 have been collected. 



OTHER SPECIES REFERRED TO PHYSOCEPHALUS SEXALATUS. 



Two other worms have been thought by different writers to be possi- 

 bly identical with Physocephalus sexalatus, viz, Simondsia paradoxa 

 (Cobbold, 1864b) from Sus scrofa domestica and Filaria nitidulans 

 (Schneider, 1866a) from Tapirus americanus. 



Simondsia paradoxa was collected from the stomach of a German 

 hog kept at Regent's Park, London, and was described by Cobbold 

 (1864b). In a later work (1879b) Cobbold suggests the possibility 

 of the worm being identical with Physocephalus sexalatus. The 

 immensely hypertrophied uterus of Simondsia paradoxa, forming a 

 rosette entirely covering the caudal end of the female, however, clearly 

 differentiates this species from Physocephalus sexalatus. 



