STUDIES ON SEX IN THE HERMAPHRODITE 

 MOLLUSK CREPIDULA PLANA 



II. INFLUENCE OF ENVIRONMENT ON SEX 



HARLEY N. GOULD 

 Department of Biology, Princeton University 



CONTENTS 



Introduction 225 



Degeneration of the testis in male Crepidulas 226 



Male development in neuter individuals 229 



Influence of larger on smaller males 238 



Reversibility of female differentiation 240 



Nature of stimulus to male development 242 



General considerations and comparisons 247 



Summary 248 



INTRODUCTION 



In a former paper (Gould, '17) the writer has followed out the 

 sexual cycle of Crepidula plana and has shown that the sexual 

 life of the adult may be divided into (A) the male phase, (B) the 

 transitional phase and (C) the female phase. During the transi- 

 tion period the testis degenerates and eventually all the primor- 

 dial male cells in the gonad disappear; while the primordial female 

 cells, present from the beginning, multiply, and form the ovary. 



It was also pointed out that there was great irregularity in 

 the development of the male phase. A number of specimens of 

 the same size and apparently of the same age, taken at the same 

 time of year, may show widely different sexual states. One may 

 be a fully developed male; one may be a partially developed 

 male; one may exhibit evidence of having been a male though 

 the male characters are being lost; and one may furnish no sug- 

 gestion that any male characters have ever developed. The 

 analysis of this phenomenon was reserved for the present paper; 



225 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 23, NO. 2 

 JULY, 1917 



