NOTES ON THE FREE-LIVINO NEMATODES. 437 



spermatozoa in one half of tlie genital gland only, the other 

 prodncing eggs alone. Maupas emphasises the significant 

 tact that these species with an incipient hermaphroditism 

 yiekl the highest proportion of males he was able to chronicle. 

 This conclusion that the more complete development of 

 hermaphroditism and the suppression of the male sex neces- 

 sarily proceed closely together is discussed further below. 



It is also highly characteristic of the hermaphrodite species 

 in general that the sperm each individual produces only 

 suffices for the fertilisation of a limited number of eo-os, so 

 that the period of fertility is followed by one even more 

 prolonged, during which unfertilised eggs are laid, which do 

 not develop. Such a phenomenon marks the hermaphroditism 

 of the free-living nematodes as a character comparatively 

 recently acquired and as yet not shaped by natural selection 

 in anything like its final form. 



Finally, a most interesting result was obtained by experi- 

 ments with hermaphrodites which had exhausted their stock 

 of spermatozoa and supplemental males of the same species. 

 In the rare occasions in which fecundation took place the eggs 

 which wei-e afterwards laid produced males and females in 

 equal numbers.^ 



Systematic Pakt. 



Diplogaster M. Schultze. 



This genus includes representatives both from soil and 

 fresh water. But while the former possess a weakly developed 

 bursa, which indicates the relationship of the genus to 

 Rhabditis, the latter are without this character, and this 

 fact, according to Blitschli, affords a natural distinction 

 between the classes. 



^ A preliminary note published in 1908 (" Sexual Phenomena in the 

 Free-living Nematodes," F. A. Potts, ' Proe. Canib. Phil. Soc.,' vol. xiv, 

 Pt. IV, pp. 373-5) gave a general confirmation to Maupas' results, 

 founded on observations on Diplogaster linstowi which was kept in 

 cultures for over a year and then died out. 



