370 Experimental Zoology 



In some species the females have neither the "disposition" to 

 unite with male individuals nor the apparatus for storing the 

 sperm. Males occur in some of these cases, but they also often 

 lack the sexual instinct, and their spermatozoa are condemned 

 to perish. 



Another point of great interest has been made out by Maupas, 

 viz., the imperfection or insufficiency of the hermaphroditism. 

 More eggs are produced than there are spermatozoa present to 

 fertilize them. Those that are first set free from the ovary 

 become fertilized, the rest become rapidly disorganized. The 

 number of fertilized eggs produced by a well-nourished individ- 

 ual is only about 200 to 25O. 1 This condition is far from being 

 an advantage to the species, for if separate sexes existed, at least 

 800 eggs might be fertilized. If only half of these eggs produced 

 females, still the number would be 400, which is larger than the 

 number of individuals produced by the hermaphroditic species. 

 In the second generation there would be 160,000 individuals 

 from the unisexual females, but only 60,000 hermaphroditic 

 females. Thus there is no reason to suppose that this herma- 

 phroditic condition is the result of an adaptation of the species. 

 Instead of an advantage it is a process injurious to the species, 

 but suffices, nevertheless, to keep it in existence. 



Males appear in these hermaphroditic species, but in relatively 

 small numbers. Maupas has given the proportions observed 

 in the following table : 



Diplogaster robustus .... 0.13 males 



Rhabditis guignardi .... 0.15 males 



Rhabditis dulichura . . . .0.7 males 



Rhabditis caussaneli . . . .1.4 males 



Rhabditis elyaus . . . .1.5 males 



Rhabditis coronata . . . . 5.0 males 



Rhabditis perrieri .... 7.0 males 



Rhabditis marionii 7.6 males 



Rhabditis duthiersi .... 20.0 males 



Rhabditis viguieri .... 45.0 males 



1 In one species only, Rhabditis guignardi, there are more, namely, from 520 

 to 530. 



to 1000 females 



