248 HARLEY N. GOULD 



it; and in that a substance can be demonstrated passing from 

 one to the other. There is not the least suggestion of 'para- 

 sitism' in the case of Crepidula plana. 



An instance of external conditions modifying a male gonad 

 toward the female condition, though not at all as in Crepidula 

 plana, is seen in certain Crustacea. Potts ('06) and G. Smith 

 ('10) have found in the cases of the hermit crab (Eupagurus) 

 and the spider crab (Inachus) respectively, that the presence of 

 parasites attached to the body causes a degeneration of the testis 

 in the male, and the subsequent appearance of what the authors 

 believe to be ova, in the gonad. Parasitic infection in the female 

 does not result in a modification toward the male condition. 

 Smith believes that the parasitic castration brings out a 'latent 

 hermaphroditism' in the male but not in the female. The male 

 would then be the heterogametic sex, the female homogametic. 

 The secondary sex characters are also modified from the male 

 toward the female condition in all degrees. On account of the 

 loose correlation between the changes in the secondary sex char- 

 acters and those in the gonad. Potts beheves that the former are 

 not directly consequent upon the latter, but that "both are 

 attributable to some change in the general metabolism." 



SUMMARY 



In the protandric hermaphrodite Crepidula plana the develop- 

 ment of the male phase is dependent upon the presence of a 

 larger individual, not necessarily a female, of the same species. 

 It is evident that some stimulus passes from the larger to the 

 smaller individual. The greater the difference in size between 

 the animal giving the stimulus and the animal receiving it, the 

 more certain and complete is the male development of the 

 smaller. A small stimulus will initiate male development, but 

 a greater one is necessary to complete and maintain it. 



When a male becomes removed from the neighborhood of the 

 larger animal, the male organs degenerate, a condition of sexual 

 inactivity ensues, later replaced by female development. 



If a larval C. plana settles and grows during the first part of 

 its hfe where no larger individuals are present, the male phase 



