CRABS AND SHRIMPS. 



221 



~~the deeps. Others, which are more strictly oceanic, dis- 

 play the same structure in a yet higher degree. 



It is impossible to walk along a beach by the edge of 

 the tide without observing many univalve shells running 

 to and fro, with an agility far greater than that of the 

 sluggish mollusks, whose houses they originally were. On 

 looking closely at them, we see the antennse, eyes, and 

 claws of what seems a minute Lobster projecting from 

 each. If we take it up, the jealous little rogue withdraws 

 into the house, pulling his legs after him, and claps one 

 stout claw upon the other, in such a way as effectually to 

 bar the intruder's entrance. We may smash the shell upon 

 a stone, and thus execute a forcible ejection (it is no more 

 than he deserves, for the house is not his own, and he pays 

 no rent), and then we see that the hinder parts are 

 curiously distorted and twisted, to fit it for tenanting a 

 spiral shell. It is not a Lobster at all, but a Hermit-crab 

 (Pagurus), and this is the mode of life for which it is cre- 

 ated. The abdomen is covered with a soft skin instead of 

 a shelly crust, and therefore needs protection; and this 

 is provided by the instinct which teaches the Crab to search 

 for some empty univalve shell of suitable size, and to 

 appropriate it for himself. Some laughable scenes occur 

 when the old house becomes too strait for him to live any 

 longer in it, and his growirf bulk compels him to look out 

 for a new lodging. Like a sound philosopher, he never 

 loses grasp of the old shell till he has found a better. 



Tropical countries have many species of Crustacea, 

 which, from their terrestrial habits, are denominated Land- 

 crabs. Those of the West Indies (Gecarcinus) make bur- 

 rows in the soft earth, whence they wander by night for 



