STUDIES ON SEX IN THE HERMAPHRODITE 

 MOLLUSC CREPIDULA PLANA 



I. HISTORY OF THE SEXUAL CYCLE 



HARLEY N. GOULD 

 Department of Biology, Princeton University 



EIGHTY-FIVE FIGURES 



CONTENTS 



Introduction 1 



Material and method 3 



Care of live material 3 



Fixation of specimens 3 



Natural history of Crepidula plana with discussion of former work on 

 hermaphroditism in Calyptraeidae 



Relation with hermit crabs 4 



Formation of the shell 4 



' Environmental polymorphism' 5 



I Motility of males 8 



Variations in sexual development 8 



Genital organs of the Calyptraeidae 10 



Observations on Crepidula plana 11 



Establishment of the gonad and efferent duct 11 



Types of germ cells! 12 



Follicle cells 15 



Male development in the gonad 17 



Development of the Apyrene spermatozoa in Crepidula plana 21 



. . -The adult testis 28 



THistory of the gonad from male to female phase 30 



Regression of the testis 30 



Development of the ovary 33 



History of the accessory reproductive organs 35 



The undifferentiated goniduct 35 



Development of the accessory male organs 37 



Time of development of the male organs 37 



Contents of the seminal vesicle 38 



Degeneration of the accessory male organs 39 



Development of the accessory female organs 42 



General considerations: Origin of germ cells in hermaphrodite molluscs. ... 46 



Bibliography 50 



1 



THE JOURN.^L OF EXPERIMENTAL ZOOLOGY, VOL. 23, NO. 1 

 MAY, 1917 



