NEMATODE GENUS PHYSALOPTERA. 1007 



viz. : (1) a posterior and short but elongately pyriform ejacu- 

 latory duct, with its thickest part away from the genital orifice : 

 (2) a long vesicula seminalis, of the same dimensions throughout 

 and slightly thicker than the ejaculatory duct ; and (3) a much 

 thinner and tapering testis, which passes forwards into the 

 anterior third of the body, after which it recurves, and passes 

 backwards to end at about the middle of the body. The ejacu- 

 latory duct and vesicula seminalis are straight, but the testis 

 performs irregular longitudinal loops in its forward course. The 

 accessory male genital appai-atus consists of two spicules, of which 

 the left is generally long and slender, and the right shorter and 

 stouter; they may, however, be of the same length, or the right 

 may be slightly larger than the left. 



Characters of Systematic Importance. 



Seurat (1914) was the first to draw attention to the systematic 

 value of the number of the uteri, and in his writings on the 

 Physaloptera invariably groups his species according to whether 

 they have two or four uteri. In my investigations on this genus 

 I have found also forms possessing as many as 15 uteri, and con- 

 sequently have classified them into the three groups — Didelphys, 

 Tetradelphys, and Polydelphys. 



The number of the uteri and their mode of origin from the 

 ovijector appear to me to be characters of primary systematic 

 value, and the question arises whether the}^ are not of generic 

 significance. 



Irwin-Smith (1922) considers it " undesirable to establish a 

 new genus entirely on a character which can be determined only 

 by dissection." I agree with her that it does not appear legitimate 

 to create a genus on only one character ; and consequently I have 

 looked for some other characters common to each of these groups, 

 but have not been able to find any. The whole genus is so 

 compact, and its individual species have so many characters in 

 common, that at the present state of our knowledge of the 

 Physaloptera, I am compelled to retain them all in the same 

 genus, however much I have felt inclined to split them up for the 

 sake of convenience. 



Travassos (1920) separates from the genus Physaloptera four 

 new genera, limiting the genus Physaloptera to those forms 

 possessing similar and subequal spicules, two uteri, four pairs of 

 pedunculated papillae, and having no reduplication of the cuticle 

 over the caudal extreaiity. He gives the following key to these 

 five and three other nearly related genera : — 



1. Spicules similar and subequal. 



A. Two uteri. 



a. Four pairs of pedunculated papillae ; no prepuce-like sheath 



at tiie posterior extremity Physaloptera . 



h. A prepuce-like collar present at the posterior extremity ... Gldamydonema. 



c. Eight pairs of pedunculated papillsa Thuhuncea. 



B. Ten uteri ... Turgida. 



