CH. XXI.] VARIOUS SPECIES OF CRABS. 289 



along the line of empty shells and pebbles formed 

 by the last wave, and unwilling to part with even 

 an incommodious habitation before it has acquired 

 a new one, it is seen stopping, first at one shell, 

 turning it about, examining it, and passing it by ; 

 then proceeding to the next, which seems more 

 convenient, slipping its tail out of its old shel) and 

 trying it in the new, and again returning to the old 

 one if this should not suit it. In this manner it 

 proceeds until it has found one sufficiently light and 

 commodious, which it selects, although it should 

 even be so large as to hide the body of the animal, 

 claws and all. Combats even sometimes occur be- 

 tween two crabs for the possession of some well- 

 looking shell upon which they may both have fixed, 

 and of which each endeavours to take possession, 

 striking at and biting each other with their claws, 

 till the weakest is obliged to give up all pretensions 

 to the object of dispute. When this crab is laid 

 hold of it emits a slight noise or cry, and endeav- 

 ours to seize its adversary with its nippers $ and, 

 should it succeed in laying hold, it will rather die 

 than quit its grasp. 



The Pea-crabs (Pinnotheres Pisum) exemplify, in 

 a no less degree than the hermit-crabs, the same 

 admirable adaptation of habits to the structure of 

 an animal which we have already alluded to in 

 speaking of the latter. They are of small size, 

 and, unlike the latter, are parasites upon various 

 living molluscous animals, which inhabit bivalve 

 shells, which the females never afterward quit, and 

 enclosed in which the females not only grow but 

 breed. Muscles are occasionally infested with these 

 crabs ; and it is interesting to observe, that the small 

 rounded form of this animal especially adapts it for 

 making its way through the valves of the shell of an 

 animal which would instantly endeavour to close 

 the passage were it a larger one, or one unable to 

 slip readily through the entrance, Aristotle was 



VOL. IL B b 



