466 STANLEY C. BALL 



Methods 



Observations made on the living worm slightly compressed 

 beneath a cover slip enable one to make out the genital pore, 

 ovaries, testes, seminal vesicle and vitellaria. But for the 

 genital ducts this method proved unsatisfactory. In one in- 

 stance a mass of spermatozoa was distinguished in the atrium 

 of a specimen which lay with its ventral surface up. 



The most reliable and complete data were obtained from sec- 

 tions of the worm. Of specimens killed in corrosive sublimate, 

 Zenker's fluid and strong Flemming solution and subsequently 

 stained with iron haematoxylin, those killed in Flemming solu- 

 tion gave the most satisfactory results, both as to preservation 

 and stain. In most cases Orange G was used as a counter stain. 



Material fixed in corrosive-acetic and stained in Ehrlich's 

 haematoxylin was excellent for the study of tissues in which 

 the exact condition of the chromatin was of minor importance. 

 Nuclei, as a whole, show much more plainly when treated by 

 this method than when iron haematoxylin is used. Here again 

 orange G was used as a counter stain. In connection with the 

 study of sectioned material living embryos of various stages, 

 removed by pressure from the mother, furnished checks on many 

 points. A few useful total mounts were prepared. 



III. ANATOMY OF THE ADULT REPRODUCTIVE ORGANS 



The male organs 



Like the related forms described by Bresslau, Hallez, von 

 Jhering and von Bohmig, Paravortex is protandrous. In half- 

 grown individuals the male organs are well developed. The 

 testes lie one on either side of the body close behind the pharynx 

 (fig. 3). A large seminal vesicle lies just above the genital 

 pore which opens in the midline of the ventral surface about 

 one-third the distance from the anterior end of the body. Two 

 short vasa deferentia lead from the inner posterior margins 

 of the testes to the seminal vesicle. A common atrium inter- 

 venes between the seminal vesicle and A-entral body wall in such 

 a way that the plug-like penis, situated in the small atrium 



