1909.] Hermaphroditism in Mollusc Crepidula fornicata. 



471 



such outgrowth on the head, hut possessing a slightly spirally constricted 

 tube, the uterus or external part of the oviduct, projecting on the right side 

 of the mantle, were apparently called females (fig. 2, ? ). In dissecting a 

 number of these animals I came across an hermaphrodite form, that is a 

 form possessing both penis and uterus as in fig. 2 £ . 



Before the commencement of this work, Prof. Dendy had kindly given me a large 

 collection of the radulse of Crepidula fornicata obtained by him at West Mersea, 

 suggesting that I might investigate and compare the variability of the English and 

 American stocks with respect to radular characters. I took the matter up, but after reading 

 Prof. Conklin's work (2, pp. 19 to 25), on the genus Crepidula, decided to extend the 

 investigation. Fresh material was obtained from West Mersea, and all of this was 

 preserved in order to permit of correlation of all characters. 



It was thought that the chain relations of individuals, and the sex relations 

 in the chain would be interesting. A few entire chains were therefore 

 preserved, and the relative position of the individuals recorded : thus the 

 sex relations of the individuals in the chains were brought out as displayed 

 in Table I. 



Table I. 



Eef. No. 



A. 



B. 



c. 



D. 



E. 



F. 



a. 



H. 



I. 



Chain 1 



? • 



• 9 ■ 



.. 9 .. 



■ 9 • 



• § ■ 



. 3 ■ 



■ 3 ■ 



. 3 



• 3 : 



„ 2 



? • 



• 9 • 



.. ? .. 



• 3 ■ 



■ 3 ■ 



■ 3 ■ 



■ 3 : 







„ 3 



9 • 



• 9 • 



.. ? .. 



• 9 • 



• 9 • 



■ § ■ 



■ 3 ■ 



. 3 



■ 3 : 



„ 4 



? • 



• 9 ■ 



.. ? .. 



. 3 ■ 



• i ■ 



■ 3- 









„ 5 



9 • 



• 9 • 



• • 3 















» 6 



9 •■ 



■ 9 • 



. lost . . 



■ 3 ■ 



■ 3 ■ 



■ 3 ■ 



■ 3 ■■ 

























In Table I the individuals in a chain are denoted by the letters, A, B, C, . . . 

 etc., the proximal individuals being denoted by A, the next to the proximal 

 by B, and so on. The chains therefore, read horizontally : — 



Forms with a well-developed penis are represented by the symbol $ 

 „ „ uterus „ „ ? 



,, „ penis and uterus „ • £ 



If the chains were found to be naturally complete,* two dots are placed after the last 

 symbol, thus — 3 '• 



If the chain were doubtfully complete, one dot was placed similarly, thus — 3 • 

 If the chain were known to be incomplete, only the symbol was used — $ 



* Usually, in a naturally complete chain, the " distal " individual is a very young one. 

 If, however, the distal individual is large, one can generally tell if it has had another 

 individual on its back by the absence of the periostracum in an elliptical area on the right 

 side of the shell. 



2 M 2 



