306 SUPPLEMENT 



choose another more spacious. For this purpose it enters 

 successively, and backwards, into almost all the empty shells 

 with which it meets. It endeavours to discover that in which 

 the hinder part of its body will be most at ease; and unless it 

 be favoured by chance, it is frequently unable to lodge itself 

 until after many trials and examinations. 



In their youth, these Crustacea sink down almost entirely in 

 their shells, and scarcely can the extremity of their feet be 

 perceived ; but when more advanced in age, and increased in 

 bulk, their claws and the two or four following feet always 

 show themselves, in a great measure, outside. When their 

 pincers are of a very unequal size, the largest often closes the 

 entrance of the shell, in the manner of a lid. The same spe- 

 cies of pagurus lodges in univalve shells of different species, 

 and even of different genera. " But," says Olivier, " what 

 appears to us not to have been sufficiently observed, though 

 well worthy of observation, is, whether the same individual, 

 on quitting its shell now become too small for it, proceeds 

 constantly to lodge in a shell similar to the first ; whether 

 it confines itself to certain species of the same genus ; or 

 takes indifferently all which present themselves, no matter to 

 w^hat species they may appertain. Might it not be possible 

 that the individual which at first inhabits a buccinum, and 

 in which its body is in some sort modelled, could not after- 

 wards lodge conveniently but in another buccinum, and that 

 it would find itself incommoded or constrained if it wished to 

 fix itself in a murex or a tonna?" It does not, however, 

 appear, according to the opinion of this skilful naturalist, that 

 the form of the body of the pagurus is intimately adapted to 

 that of the cavity of its dwelling ; for, were it so, the indivi- 

 duals of the same species of pagurus, inhabiting shells of 

 divers species, would also present notable differences, which 

 has not been remarked, and which even cannot take place, 

 since the trunk, although of a consistence less solid than that 



