STUDIES ON SEX IN CREPIDULA U 



tinued along the posterior side of the penis to the tip. The 

 organ contains transverse and longitudinal muscle fibers and is 

 capable of great extension. 



In the female phase the reproductive organs are much in- 

 creased in size corresponding to the increased size of the whole 

 body. The goniduct is now transformed into a large ciliated 

 tube with its inner wall thrown into longitudinal folds; it is 

 about the same diameter throughout. It runs directly forward, 

 without turning upon itself, to the region where the vas deferens 

 formerly opened into the sperm groove; but we now find there 

 a large uterus with thick glandular walls. It is usually ciliated 

 on the inner surface. Several seminal receptacles for the stor- 

 age of sperm open into it. They consist of non-ciliated sacs 

 connecting with the uterus by small ciliated tubes. There may 

 be one common tube or as many individual ones as there are 

 receptacles. The shape of the uterus varies in different genera. 

 It may be nearly straight or may be bent tipon itself; it often 

 shows a transverse segmentation externally. Two or three 

 kinds of gland cells can be recognized in its thick walls by their 

 structure and peculiar staining reactions. In some forms (e.g., 

 Crepidula peruviana [Haller]) the uterus is said to have acces- 

 sory glands which lie upon its surface. 



A structure connected with the reproductive system and of 

 doubtful function is the gonopericardial duct. It is present 

 only in the female phase. It connects the pericardial chamber 

 with the oviduct, joining the latter approximately midway be- 

 tween the ovary and the uterus. 



The Calyptraeidae, like many other Prosobranchs, have, so 

 far as described, the 'atypical' as well as the typical or true 

 sperm. 



OBSERVATIONS ON CREPIDULA PLANA 



Establishment of the gonad and efferent duct 



In the earliest stage in which the gonad has been observed, the 

 primordium of the organ occupies a position in the anterior re- 

 gion of the visceral sac, underneath and to the right of that por- 

 tion of the intestine, which after leaving the stomach runs 



