38 PAUL PELSENEEK. 



individuals accidentally present a unisexual genital apparatus, 

 they are always female; it is always the female sex which 

 reappears. 



a. Clio (Hyalocylix) striata, without penis, cited above 

 (III, note, according to Schiemenz). 



b. Cymbuliopsis calceola, without penis (48c). 



c. Agriolimax laevis, without penis, having never been 

 male (adult female; 49). 



d. Helix aspersa, without vas deferens, penis, and flagel- 

 lum(49a). 



e. Arion intermedins, without male reproductive organs 

 (49b). 



VI. Conclusions. 



Granted, then, that in Mollusca hermaphroditism has suc- 

 ceeded a unisexual state, and that it has been superimposed 

 upon the female condition, is this process paralleled in other 

 groups ? 



I. The origin of hermaphroditism in a unisexual 

 condition. — I have not been able to make any special investi- 

 gations upon hermaphroditism in the various groups of the 

 animal kingdom. It seems to me, however, that if we examine, 

 by the comparative method, the data which we already possess 

 upon the subject, we must come to the conclusion — opposed to 

 the ordinarily received opinion, which possesses the authority 

 of the names of Huxley, Gegenbaur, Haeckel, Giard, Clans, 

 &c. — that hermaphroditism is secondary, and succeeds a pri- 

 mitively dioecious state. 



In fact, like myself, who have reached this result for the 

 Mollusca, so Beard and Delage have already formulated this 

 opinion as concerning two other groups, the Myzostomidae 

 (49e) and Cirripedes (50). And Fritz Miiller, after a more 

 general consideration of the subject, also argues against the 

 primitive nature of the hermaphrodite state, and shows that 

 in the majority of groups the most archaic forms are unisexual 

 (51). 



A survey of the various subdivisions of hermaphrodite 



