DERMO-SKELETON OF THE HERMIT CRAB. 391 



detached calcareous pieces analogous, it is true, to those found in the 

 Lobster, but strangely altered in structure. 



(1000.) These animals (fig. 199), usually known by the name of 

 Soldier Crabs, or Hermit Crabs, frequent level and sandy shores, and, 

 from their defenceless condition, are obliged to resort to artificial pro- 

 tection. This they do by selecting an empty turbinated shell of propor- 

 tionate size, deserted by some gasteropod mollusk, into which they in- 

 sinuate their tail, and, retreating within the recesses of their selected 

 abode, obtain a secure retreat, which they drag after them wherever 

 they go, until, by growing larger, they are compelled to leave it in 

 search of a more capacious lodging. The wonderful adaptation of all 

 the limbs to a residence in such a dwelling cannot fail to strike the 

 most incurious observer. The chelce, or large claws, differ remarkably 

 in size; so that, when the animal retires into its concealment, the 

 smaller one may be entirely withdrawn, while the larger closes and 

 guards the orifice. The two succeeding pairs of legs, unlike those of the 

 Lobster, are of great size and strength, and, instead of being terminated 

 by pincers, end in strong pointed levers, whereby the animal can not 



Fig. 200. 



Swimming Crab. 



only crawl, but drag after it its heavy habitation. Behind these loco- 

 motive legs are two feeble pairs, barely strong enough to enable the 

 Soldier-Crab to shift its position in the shell it has chosen ; and the 

 false feet attached to the abdomen are even still more rudimentary in 



