482 Mr. J. H. Orton. Occurrence of Protandric [June 8, 



such animals the penis is usually very small, and in some cases has almost 

 entirely disappeared. Quite a complete series of stages in the degeneration 

 of this organ was observed from the fully formed organ on the one hand to a 

 minute papilla on the other. Sections of such animals show that neither 

 male nor female sexual cells are produced at this time (!) The evidence seems 

 to favour the view that we have in these cases an example of protandric 

 hermaphroditism, but I am not able to assert that this is really the case, 

 although I have spent much time in attempting to decide it." 



From these quotations the following facts are brought to light : — 



(1) The males in all species of Crepidula are smaller on the average than 



the females. 



(2) The females of the species of adunca, navicelloides, and plana are fixed, 



but the males are motile. 



(3) The adult females and males of C. convexa are motile to a limited 



extent. 



In the light of the present observations on Crepidula fornicata, I have no 

 hesitation in concluding that C. plana is also a protandric hermaphrodite, as 

 Prof. Conklin suspected. It is highly probable also that the species, adunca 

 and navicelloides are protandric hermaphrodites, but there is not sufficient 

 evidence available for a judgment on C. convexa* 



A careful research on the proportions of the young males and females, and 

 on the sexual character of the young of the various species of Crepidula, may 

 bring out an interesting series of stages in the evolution of protandric 

 hermaphroditism. 



Sex Phenomena in the Streptoneura. 



It is significant that Pelseneer should remark (6, p. 124) that " sedentary 

 species (of Gastropods) often possess a rudimentary penis." Stimulated by 

 this statement, I examined a collection of 160 Calyptrcea chinensis, and found 

 that all the small ones, about half the number examined, were <J 's, while 

 the larger ones were either $ , $ p.r., or ? , but were nearly all ? p.r.'s. 

 Since all the small ones are males, however, it would seem that this species- 

 is also a protandric hermaphrodite. An investigation is being made of the 

 primary sexual characters to decide the question. It is probable, therefore, 



* July 20. — Since the above was written, Mr. E. Smith has drawn my attention to a 

 chain of C. navicelloides (probably EE batata), exhibited in the cases of the British 

 Natural History Museum. I was kindly allowed to examine the Museum collection of 

 Calyptrseidae, and in a collection of G. dilatata from Ancud I found the following chain — 

 A, ? p.r.; B, ^. In another collection of the same species from Patagonia, out of seven 

 individuals the three smallest were <?'s, the others being either ? p.r. or ?. Thus 

 stronger evidence is adduced for the above statements. 



