4 HARLEY N. GOULD 



Of all the common stains, iron haemotoxylin, either alone or in 

 combination with eosin or light green, was most satisfactory. 

 Delafield's haemotoxylin was occasionally used. 



NATURAL HISTORY OF CREPlDULA PLANA WITH DISCUSSION OF 

 FORMER WORK ON HERMAPHRODITISM IN CALYPTRAEIDAE 



A . Relation with hermit crabs 



Although the natural history of C. plana has been described 

 by Conklin ('97) it is necessary for the sake of clarity in subse- 

 quent parts of the discussion to state some facts regarding its 

 mode of life, which is intimately connected with and greatly 

 dependent upon the activities of the large hermit crab, Eupa- 

 gurus bernhardus. The hermit crabs may be picked up just 

 below low-tide mark along flat, sandy beaches where the water 

 is comparatively quiet. The Crepidulas adhere to the inside 

 of the empty Gastropod shell which the hermit crab occupies, 

 usually with their anterior ends directed toward the opening 

 of the shell. Associated with each hermit crab may be a vary- 

 ing number of Crepidulas. Some of the shells used by the her- 

 mits are very large and afford room for the attachment of a 

 great number of the small Molluscs. Those shells which give 

 evidence of having been long occupied by the crab bear larger 

 and more numerous Crepidulas than the shells where a glossy, 

 pearly appearance indicates that the Gastropod has only re- 

 cently died and the hermit assumed possession. 



B. Formation of the shell 



It was shown in Conkhn's ''Embryology of Crepidula" ('97) 

 that the individual differences in the shape of Crepidula's own 

 shell vary according to the surface on which the animals live 

 and grow. It is convex on a convex surface, concave on a con- 

 cave surface, thick when the mantle cannot be readily extended, 

 thin when it can; for the shell is deposited by the mantle, and 

 the latter readily adjusts itself over the substratum. 



The shape of the Crepidula shell naturally shows striking 

 differences in the sparsely populated 'new' hermit crab shells 



