1909.] Hermaphroditism in Mollusc Crepidula fornicata. 



475 



of Stages I, II, and III are found, I have no doubt that chains are formed as is 

 indicated above. The relative frequencies of different lengths of chains in all 

 the chains examined — including those in Table V — may be gathered from a 

 glance at the curve in fig. 3. 



From fig. 3 it is seen that the longer the chains are the less frequently do 



I 2 3 4 5 6 7 8 9 IO II 12 .. 



No. of individuals. 



Fig. 3. — Curve showing frequencies of different lengths of chains among 336 chains. 

 Ordinates = frequencies ; abscissse = individuals in chain. 



they occur. Chains of 9, 10, and 11 individuals were not recorded once, and 

 only one chain of 12 individuals was seen. 



The age of change from £ to ? , and the length of time required for the 

 formation of a chain of given length are being investigated. 



Some points in the records of the chains are noteworthy. The scarcity of 

 3 u.r.'s is noticeable. Probably their rarity may be accounted for by the 

 following facts. 



(1) The uterus develops in the wall of the mantle, and is not visible 



externally until partly developed :* only those individuals were 

 -recorded as £ u.r.'s in which the end of the uterus projected from the 

 mantle. 



(2) The chains have only been examined between February and May this 



year : it is possible the change may occur rapidly at some other 

 period of the year. 



Single chains often afford evidence of the change from to ? ; such 

 a series as ? p.r. °. p.r. § is common ; moreover, in these cases a 

 gradual decrease in size of the penis, from the to the proximal 

 ? p.r. is also often observable ; a point not brought out in the 

 records. 



* The development of the uterus is being investigated. 



