254 THE SOCIAL LIFE OF ANIMALS 



is dead. Attached to its shell is a large female which 

 in summer actively produces eggs. Above her are 

 two individuals that are undergoing transformation 

 from male to female. Scattered about over these are 



Fig. 45. Crepidula fornicata. (A) A basal female is 

 attached to a dead shell (D); two individuals are in tran- 

 sition stages and there is one male at the apex; three 

 motile supplementary males are in mating position on 

 the lower transition individual. (B) same group from the 

 left side. (From Coe.) 



four smaller snails which are still functional males 

 and which can and do move about. Each male has 

 a long slender penis by means of which he transfers 

 sperm from his body to an appropriate receptacle 

 in the body of the female. Several males may par- 

 ticipate in the insemination of a single female. 



The growth of these snails is fairly rapid. A young 

 snail hatched out early in the summer may, before 

 autumn, become a functional male about 16 mm. 

 long, which is about two-fifths the size of a fully 



