Prosobranchiata 531 



The young slugs are fed upon white bread, raw potatoes, and lettuce 

 for a few days and then any of the above foods may be given. If the 

 food becomes moldy, the young slugs should be transferred to another 

 petri dish and given fresh food. 



Bibliography 



Carmichael, E. B. 1928. Action of ultra-violet rays on Limax flavus Linnaeus. 



Amer. J. Physiol. 85:358. 

 1931- The action of ultra-violet radiation on Limax flavus Linnaeus. I. The 



varying effects on non-pigmented and pigmented embryos. Physiol. Zool. 4:575. 

 Carmichael, E. B., and Rivers, T. D. 1932. The effects of dehydration upon the 



hatchability of Limax flavus eggs. Ecol. 13:375. 



References 



Order Opisthobranchiata 



For the rearing of Tethys californicus see p. 197. 



Order prosobranchiata 



THE GENUS CREPIDULA 



E. G. Conklin, Princeton University 



CREPIDULA is a genus of prosobranchiate gastropods which is 

 represented on the Atlantic coast of the United States by the 

 species, C. plana, C. convexa, and C. jornicata, and on the Pacific coast 

 by C. adunca and C. navacelloides. All of these species are relatively 

 abundant and all furnish unusually favorable material for embryological 

 research. They are all sessile or sedentary when adult and are usually 

 found attached to shells inhabited by hermit crabs. C. plana is usually 

 found on the inside of such shells, C. convexa and C. jornicata on the 

 outside, although the latter is sometimes found on Limulus and also in 

 chains, one on top of another, the first one frequently being attached 

 to a stone. The shells of adult specimens take the form of the surface to 

 which they are attached and on small surfaces or inside the shells 

 occupied by the small hermit crab, Eupagurus longicarpus, the Crepi- 

 dulas are dwarfed so that sexually mature individuals are sometimes 

 only y 2 5 the volume of others whose growth is not so limited. Males are 

 smaller than females and in C. plana and C. convexa they are motile; 

 later as they grow larger they become sedentary and transform into 

 females. 



Eggs are laid in thin transparent capsules which are attached to the 

 substrate within the mantle cavity of the female. The average number 

 of eggs laid by each species is approximately inversely proportional to 

 the size of the eggs and to the length of larval life, and directly pro- 



