No. I.] 772^^ EMBRYOLOGY OF CREPIDULA. 9 



suits, though many other stains were useful, particularly the 

 Biondi-Erlich mixture and the iron haematoxylin of Heidenhain. 

 One other thing ought to be mentioned in this connection. 

 I have in no instance been able to follow any one lot of eggs 

 throughout any considerable part of their development. When 

 removed from the mantle cavity of the mother they do not 

 develop normally for more than two or three days. I tried 

 keeping some of the eggs in small dishes, changing the water 

 twice a day ; others were placed in a large jar, in which the 

 water was continually aerated by a stream of air ; still others 

 were placed in a jar, the mouth of which was covered by silk 

 netting, and the jar was then inverted in a tank of flowing 

 water ; the most successful method, however, was to put the 

 eggs in open bottles, which were then placed in an aquarium 

 through which water was constantly flowing. Yet by none of 

 these methods could the eggs be kept normal for more than a 

 few days. It would seem that the circulation of water within 

 the mantle chamber of the mother is more perfect and gentle 

 than could be obtained by any method which I could devise. 

 It was necessary, therefore, to take eggs from a large number 

 of individuals in order to get a complete series, since all the 

 eggs laid by one individual are in nearly the same stage of 

 development. Fortunately, there are such vast numbers of 

 fertile females during the breeding season as to make this an 

 easy task. 



B. THE GENUS CREPIDULA. 

 I . Natiwal History. 



At least three species of the genus Crepidula are found on 

 the Atlantic coast of the United States,^ viz., C. fornicata Lam., 

 C. plana Say, and C. convexa Say, all of which are quite abun- 

 dant along the shores of New England. All these species are 

 more or less completely sedentary, and they show the most re- 

 markable individual differences in the shape of their shells due 



1 Other species have been described, viz., C. unguiformis Stimson, C. glauca 

 Say, C. acuta Lea. Concerning the first of these there is no doubt that it is iden- 

 tical with C. plana, and I am convinced after a careful anatomical and embryolo- 

 gical examination of the last two that they are only local varieties of C. convexa 

 (cf. Verrill '74) Invertebrate Animals of Vineyard Sound. 



