Miscellaneous. 101 



after stretching backward and forward, they settled down into their 

 shells with immense satisfaction. The crabs who wore so unfortunate 

 as to obtain for their share living shells, remained riding round upon 

 the mouth of their future dwelling, and on the death of the mollusk, 

 which generally occurred soon after in captivity, commenced at once 

 to tear out the animal, and having eaten him, proceeded to take his 

 place within the shell. 



It is, of course, very difficult to apply to Invertebrates many of 

 the laws of natural selection ; and thus far we know so little of the 

 habits of most of our marine animals, that it is idle to speculate upon the 

 effect of causes which may effectually modify the life of higher animals. 

 In the case above mentioned, there is no possible connexion between 

 the embryo and the parent to account for the young having learned 

 from the former the use of the shell and its value for his existence. 

 We can therefore onl)' explain the faculty of performing this act as 

 inherited, or else as a simple mechanical act rendered necessary by 

 the conditions of the young hermit crab. The latter seems the more 

 probable case from the nature of the test of the hermit crab in its 

 younger stages, \yhile the young hermit crab, soon after leaving 

 the egg, is still provided ^vith its powerful temporary swimming-feet, 

 and while the feet of the adult can only be traced as mere rudiments 

 behind them, the whole test of the cephalothorax and abdomen (which 

 are symmetrical) is of considerable consistency up to the last 

 moults preceding the stage when it seeks a shell. At that time 

 the young are no longer symmetrical, the feet, which are now fully 

 developed, being largest on the right side, and the abdomen begin- 

 ning to curve in the same direction away from the longitudinal axis. 

 When the moult has taken place which brings them to the stage at 

 which they need a shell, we find important changes in the two hind 

 pairs of feet, now changed to shorter feet capable of propelling the 

 crab in and out of the shell ; we find also that all the abdominal ap- 

 pendages except those of the last joint are lost : but the great distinc- 

 tion between thi« stage and the one preceding it is the curling of the 

 abdomen ; its rings, so distinctly marked in the pre\dous stages, are 

 quite indistinct, and the test covering it is reduced to a mere film, 

 so that the whole abdomen becomes of course very sensitive. It is 

 therefore natural that the young crab should seek some shelter for 

 this exposed portion of his body ; and, from what I have observed, 

 any cavity will answer the purpose — one of the young crabs having 

 established himself most comfortably in the anterior part of the cast 

 skin of a small isopod, which seemed to satisfy him as well as a shell, 

 there being several empty shells at his disposal. This mechanical 

 explanation stiU leaves unanswered the eagerness with which the 

 crabs rushed for the shells, their careful examination of the openings, 

 their taking the animal out and occupying its place — all acts which 

 seem to require considerable intelligence (?) and to show remarkable 

 forethought (?). — SilUmans American Journal, October 1875. 



Newport, August 2H, 187o. 



