NOTES ON THE FREE-LIVTNG NEMATODES. 451 



angled trangle, with an indentation at the anterior angle. In 

 the other two the angles become inore and more rounded. 



In Rhabditis sechellensis variations in the secondary- 

 sexual characters are occasionally found, but are much less 

 numerous than in Diplogaster maupasi. Such variability 

 as was observed was manifested in (1) inequality of the 

 copulatory spicules, and (2) occasional asymmetrical dis- 

 j)Osition of the rays of the bursa. 



The only reference to analogous phenomena which occurs 

 in Manpas' paper is found in his description of Rhabditis 

 guignardi (p. 525). He obtained only two males, but in 

 one of these the copulatory bursa possessed on each side nine- 



Text-fig. 5. 



B. 



supporting rays, in the other only seven. In the latter the 

 remaining rays showed a disposition to fuse with each other, 

 a phenomenon, it may be remarked in passing, which was 

 responsible for the asymmetry of the bursal rays in R. 

 sechellensis. The entire disappearance of two rays is a 

 variation as great as any recorded above for Diplogaster 

 maupasi. 



The position and number of bursal papillae or rays is looked 

 upon as clearly diagnostic of species of Rhabditis or 

 Diplogaster, and as far as I know no striking variation has 

 ever been observed in the bisexual species. The connection 

 of such a variability in the males with their disappearance 

 fi'om the economy of the species is no doubt significant, but 

 it is impossible to offer any explanation of the facts. 



