HALF AN HOUR WITH CRUSTACEA. 245 



protected by a living crust as with the lobsters. 

 Hence the necessity for it to make up for this im- 

 portant deficiency by a valuable instinct, which 

 prompts it to seek out empty univalve shells, and to 

 thrust into them its soft and defenceless hinder part. 

 The fore claws are covered with the usual hard 

 crust, one of them being longer than the other, and 

 used to block up the hole of the shell when attacked, 

 on the plan of an operculum. Whilst the Hermit- 

 crab is growing, these claws, &c., moult, as in the 

 ordinary crabs, and accordingly the animal has to 

 pull himself out of his old lodgings, and seek another 

 and a larger. The way in which it tries each shell 

 by inserting its soft belly into it, just as a country- 

 man will try on half-a-dozen pairs of boots before he 

 is fitted, is exceedingly comical. The end of the 

 abdomen is provided with certain appendages, by 

 means of which it can hold on to the interior of the 

 borrowed shell. These are under the perfect 

 control of the animal, which can let go at will. 

 There are nearly a dozen species of British Hermit- 

 crabs, nearly all of which inhabit different species 

 of empty univalves. One of these crabs (Pagurus 

 Prideauxi) is remarkable for its always being ac- 

 companied by a sea-anemone; a circumstance we 

 noticed in our chapter on sea-anemones. 



In addition to the foregoing, there is a group of 

 pigmy crustaceans common in our seas, which may 

 be found more or less abundantly in the rock-pools 

 at low water. These belong to the family Pyeno- 



