238 



HARLEY N. GOULD 



Neuter specimen returned to hermit shells free from other Crepidulas; sectioned 



after seventy-jive days^ 



1 Specimen 250 was found in the same hermit shell with 249 and attached di- 

 rectly behind the latter. The male development in 250 was undoubtedly due to 

 the proximity of the larger animal; 251 and 252 were each alone in a hermit 

 shell. 



from larger to smaller individuals. The stimulus may act upon 

 animals of quite advanced size. Its effect is seen in a very short 

 time. If male development is to go on uninterruptedly the 

 stimulus must be constantly supplied. Whenever it is removed 

 male development ceases and the male organs degenerate. 



Individuals which are free from the male-producing stimulus 

 grow much more rapidly than those which remain in the male 

 phase; and the attainment of the large size is correlated with 

 female development (tables 8 and 10). (For other factors 

 influencing growth, see former paper.) 



INFLUENCE OF LARGER ON SMALLER MALES 



In the experiments so far recorded, only large female Crepidu- 

 las were used for the purpose of causing the male condition to 

 appear or preserving it, in the smaller animals. It is important 

 to know whether the quality of inciting and sustaining male de- 

 velopment is limited to animals in the female phase. The re- 

 sults of experiment 4, table 6, indicated that larger Crepidulas, 

 though not females, might influence smaller ones. The follow- 

 ing tests were made to determine whether the presence of very 

 large males would sustain the male condition in smaller specimens. 



