THE CRUSTACEANS 



93 



Fig, 60; HEKMIT CRAB. From Life. Showing 



the lioriowed shell covered with sea weeds 



and Hydractinia. Cape Ann, Mass. 



the crab instantly Avithdraws within its shell, completely closing 

 the opening with its claws, which are of the exact shape 

 required for the purpose. 

 As the crab grows it 

 must occupy larger and 

 larger shells. These are 

 apparently selected with con- 

 siderable care, but having 

 decided upon it the crab 

 finally darts into its new 

 abode with almost incredible 

 rapidity. In common with 

 other crustaceans these crabs 

 are scavengers. They are 

 also inveterate fighters, and 

 will conquer and devour one 

 another when opportunity 

 offers. A niimber of marine 

 animals grow upon the shells, 

 which are carried^bout by hermit crabs, thus obtaining the advan- 

 tages of a wandering life. Several species of hydroids. such as 



Hjjdmctinia, cover the shells 

 with soft, pink-Avhite, velvety- 

 looking growths, while a num- 

 ber of sea anemones also live 

 upon the shells. One of these 

 called f Epizoanihus america- 

 nusj finally dissolves the shell, 

 forming a cavity within which 

 the crab continues to reside. 

 One of the most interest- 

 ing of the hermit crabs is the 

 Robber Crab (Birgus latro) of 

 the tropical Pacific Islands. It 

 is about two and a half feet 

 long, and the abdomen is soft 

 below but protected above by 

 hard plates. It lives within deep burroAvs, and only occasionally 

 visits the Avater. It crawls to the top of the cocoanut trees, and 

 tears open the nuts for the sake of the AA-hite "meat." 



Fig. 61 



HERMIT CRAB. 

 Cape Ann, Mass. 



From Life. 



