CRAYFISH, LOBSTERS, CRABS, SHRIMPS, ETC. 119 



periwinkle shell, in which they may hide. The body is thrust 

 well into the shell and the opening guarded by the feet and claws. 

 As the crab develops it becomes more and more adapted to the 

 shell in which it is living. The abdomen remains soft and 

 follows the convolutions of the shell. Only the last two 

 abdominal appendages remain, and these are modified into 

 hook-like organs. The first two or three pairs of thoracic legs 



FIG. 45. A hermit crab, Pagarus sp. in a sea-snail shell. Upper figure 

 shows another crab removed from its shell. (Reduced.) 



become curiously modified and help close the opening of the 

 shell. The right claw is often very much larger than the left 

 and well fitted for the dual purpose of capturing prey and 

 acting as a door. As the crab grows, its adopted home be- 

 comes too small for it, and from time to time it must seek 

 larger shells. 



Some of the hermit crabs always have certain stinging 



