18 



THE ROUNDWORMS OF DOMESTIC SWINE. 



FIG. 14. PhysocephaliM sezalatus. Lateral view of 

 cephalicend. lab. p., labial papillae; ph., pharynx. 

 Enlarged. (After Von Linstow, 1879b, Pl.V, fig. 11.) 



and the descriptions of this species by European observers. As no 

 European specimens were at hand with which to compare the speci- 

 mens collected in this country, it was concluded either that the 



American form represented a 

 distinct species or else the de- 

 scriptions of European writers 

 were in error in some important 

 details. In order to determine 

 which of the two alternatives 

 was correct, specimens collected 

 in the United States were for- 

 warded to Prof, von Linstow for 

 comparison with specimens col- 

 lected in Europe, and other 

 European helminthologists were 

 asked for specimens of Spirop- 

 tera slrongylina. The specimens sent to Von Linstow were considered 

 by him to be a different species from Spiroptera strongylina. There 

 is, however, no question that certain European specimens recently 

 received from Prof. Gedoelst, of Brussels, are specifically identical 

 with the American 

 form, nor can it be 

 doubted that the form 

 taken by Railliet and 

 Henry (191 Ib) as 

 Spiroptera strongylina 

 is the same as the 

 American form. 



In regard to the 

 length of the spicules 

 of Arduenna strongy- 

 lina, the writer's ob- 

 servations are not in 

 accord with those of 

 Ciurea (1911). Meas- 

 urements of the spic- 

 ules of over 35 males 

 made with the aid of a 

 camera lucida and 

 stage micrometer 

 show that the long 

 spicule varies between2.24 and2.95 mm. in length, while the short spic- 

 ule is between 457 and 619 // in length. The corresponding measure- 

 ments given by Ciurea are, long spicule, 977 //; short spicule, 221 /t. 

 The measurements given by Railliet and Henry (191 Ib) are, long 



iomm. 



FIG. 15. PhysocepTialus sexalatus. Lateral view of cephalic end. cut., 

 cuticle; lab. p., labial papillae; ph., pharynx. X 415. (Original.) 



