294. GENETICS 



into a female. In this case we may say that some 

 secretion from the female stimulates the development 

 of the male potentialities and suppresses those of the 

 female. In fact, intermediates were produced by 

 Baltzer by allowing larvae to become attached to a 

 proboscis temporarily and then removing them at in- 

 tervals of less than four days. 



In Crepidula plana, a hermaphroditic gasteropod 

 which is normally protandric, that is, producing first 

 sperm and afterward ova, Gould has shown that the 

 presence of older individuals during the female phase 

 of development causes the production of sperm in such 

 young individuals as, when isolated omit sperm produc- 

 tion, developing instead the female phase and pro- 

 ducing ova. Here there is an animal in sensitive bal- 

 ance influenced by a secretion which probably comes to 

 it through the sea-water from individuals in the female 

 phase of reproduction. 



The problem of hermaphroditism, its mechanism and 

 relationship to bisexual reproduction, is well worthy 

 of intensive study. From such exceptions to the gen- 

 eral rule we may hope to learn much about the normal 

 mechanism of sex-determination. 



11. CONCLUSION 



Finally, one may ask, can sex ever be controlled? 

 There seem to be two avenues of approach to this 

 problem. 



The maturation, and thereby sex, in forms in which 

 the female is heterogametic, may be controlled by ex- 



