126 "TERRA NOVA" EXPEDITION. 



to that of tHe Dromiacea and Dorippidae of carrying their shelter with them by 

 means of the hinder legs, and on the other to that of the free-wandering crabs. But 

 none of these organisms lives in a habitat locally removed from that of other Eeptantia. 

 Crabs and lobsters, Porcellmiopagurus and ordinary hermit-crabs may be taken in the 

 same locality. It is with their habits rather than with their habitats that their 

 structure is correlated. Nor is it possible, in view of the fact that they possess free 

 larvae, and those of the same type, and therefore persistent from their common 

 ancestor, to construct any hypothesis which shall account for their unlikeness by 

 supposing that at some former time they were isolated in unlike conditions of life. 

 They owe their differences to themselves alone. 



There are few better instances than those afforded by carcinization of the fact that 

 the organism is, after all, the dominant factor in evolution. What is bred in the bone 

 will come out in the flesh, and Nature is no more able than Man to make silk purses 

 out of sows' ears. 



LONDON: PKINTED BY WILLIAM CLOWES AND SONS, LIMITED, DUKE STREET, STAMFOKD STKEET, S.E., AND GREAT WINDMILL STREET, W. 



