HERIVIAPHRODITISM 169 



of these organs may seem to depend on the same 

 ''relation-of-the-parts-to-each-other " on which all 

 somatic differentiation depends. 



If this were the correct interpretation then the prob- 

 lem of sex in hermaphrodites would appear in a different 

 light from the problem of sex in species in which males 

 and females occur, and the appeal would be made to an 

 entirely different principle. 



In cases where a sexual generation alternates with 

 a hermaphroditic generation, the problem of the two 



Fig. 8Q. ~ Rhabditis nigrivenosa, male (left) and female (right). (After 



Leunis.) 



sexes reappears. There is but one case in animals 

 that has been adequately worked out. A nematode 

 worm, Rhabditis nigrovenosa, lives as a parasite in 

 the lungs of frogs. It is an hermaphrodite. Its 

 eggs give rise to another generation that lives in mud 

 and slime. In this generation two kinds of individuals 

 are present — true males and females (Fig. 86) . The 

 females produce eggs, that are fertilized, and develop 



