250 HARLEY N. GOULD 



5. The stimulus does not depend upon the presence of the her- 

 mit crab with which the Crepidulas are associated; it will have 

 its effect even if the home of the colony is a fingerbowl. 



Whatever the manner of working of this peculiar adaptation, 

 there is no doubt of its great advantage to the species; for it 

 provides that the male members of every colony of Crepidula 

 plana shall quickly develop into females as soon as there is no 

 longer a larger female which requires fertilization; and also that 

 there shall be adult males in the colony ready to function as soon 

 as any individual has reached the adult female phase. 



BIBLIOGRAPHY 



Baltzer, F. 1914 Die Bestimmung des Geschlechts nebst einer Analyse des 



Geschlechtsdimorphismus bei Bonellia. Mitt, aus der Zool. Sta. zu 



Neapel, Bd. 22, No. 1, pp. 1-44. 

 CoNKLiN, E. G. 1898 Environmental and sexual dimorphism in Crepidula. 



Proc. Acad. Nat. Sci., Philadelphia, 1898, pp. 435-444. 

 Gould, H. N. 1917 Studies on sex in the hermaphrodite Mollusc Crepidula 



plana. I. History of the sexual cj'^cle. Jour. Exp. Zool., vol. 23, 



no. 1. 

 Potts, F. A. 1906 The modification of the sexual characters of the hermit 



crab caused by the parasite Peltogaster. Quart. Mic. Jour., N. S., 



vol. 50, p. 599. 

 Smith, G. 1910 Studies in the experimental analysis of sex. Quart. Jour. 



Mic. Sci., N. S., vol. 54, pp. 577-604. 



