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In some genera both hands are alike ; in others the left one is 

 the larger. In the case of hermits which live in tooth-shells, the 

 right hand is cylindrical in form, fitting the circular opening of 

 the shell. The other extreme is found in the genus Cancellus, 

 where both the chelipeds and the first pair of ambulatory feet 

 are ingeniously shaped, so that when closed they form a round 

 operculum, or door, which closes the way into the compact sponge 

 which this crab has for its carcinrecium, or house. It is interest- 

 ing to note these differences and observe the perfection with 

 which the feet are formed and jointed to suit the openings of 

 different shells. Some genera show other adaptations to their 

 twisted houses, the eye-stalks being uneven in length and the 

 ambulatory feet unequal on the opposite sides. Besides this, 

 some species are hairy and cover themselves with dirt for further 

 protection. The exposed claws of some hermits have a special 

 armature of spines, which make a fringe of points around the 

 opening of the shell when the crab is withdrawn. 



As the hermit grows he is occasionally obliged to find a new 

 or larger shell, and there are amusing anecdotes of the troubles 

 he experiences at these times while house-hunting. Very often 

 he tries several shells before he finds one to fit. There is a tradi- 

 tion, not, however, well authenticated, that if the shell chosen 

 happens to be occupied by its natural owner, the crab tears out 

 and devours the unfortunate occupant. If the desired shell is 

 occupied by another hermit inferior in strength to himself, he 

 proceeds to take possession by violence. He then examines care- 

 fully the empty shell, inserting his legs and feelers, and if he 

 decides to occupy it he withdraws his abdomen from the old 

 shell and darts it so quickly into the new one that the act of 

 transference is difficult to follow. After walking about with the 

 new shell it sometimes proves to be unsatisfactory and further 

 search becomes necessary. After it is well domiciled the crab never 

 ventures outside the shell until it is obliged to change again on 

 account of growth, or because some stronger crab dispossesses him. 

 The shells of hermit-crabs serve frequently as the home of other 

 animals which live with them a commensal life. The hydroid 

 Hydractinia polyclina often covers the exterior of such shells with a 

 brown, velvety growth. Some sea-anemones also are commensals 



