NOTES f)N THE FREE-LIVING NEMATODES. 483 



Summary of Eesults. 



In the preliminary summary on page 43G, a short statement 

 is given of Manpas' results alone. In the present paper these 

 are completely confirmed where the material allowed, and in 

 some of tlie following details the study of hermaphroditism in 

 Rhabditis and Diplogaster lias been pursued further. 



(1) In one hermaphrodite species, Diplogaste r maupasi, 

 the residual males ai-e much more numerous than in any other 

 yet studied, and in small cultures may reach 30 per cent, of 

 tlie whole number of individuals. 



(2) The Jtiale secondarN' sexual chararacters, i.e. bursal 

 papillre and accessory copulatory spicule, show great varia- 

 bility. 



(3) The production of males is cyclical, periods (eaoli lasting 

 a few generations) when males are frequent altern;iting with 

 others in which only hermaphrodites are produced. 



(4) Attempts to affect the sex-ratio artificially proved un- 

 successful. It was also found impossible to increase the pro- 

 portion of males by selection from favourable cultures. No 

 rule could be discovered governing the constant fluctuations 

 of production. 



(5) Even when males were most common there was do 

 tendency to find female or partially hermaphrodite individuals, 

 and the males were sexually inactive. This contrasts with 

 the conclusions reached by Maupas on Rhabditis. 



(6) The number of fertile eggs laid by D. maupasi is 

 subject to wide variation. 



(7) In Rhabditis gurneyi a far greater number of fertile 

 eggs may be produced by single individuals than in any other 

 hermaphrodite species. The fertility is probably as great as 

 the average bisexual species. 



(8) Tlie formation of spermatozoa is not coufiued to tlie 

 anterior end of the gonad as in other species, but may occur 

 in any part and at any time throughout maturity. Frequently 

 a number of sterile eggs were laid at the onset of maturity 

 owing to the retarded production of the spermatozoa. 



