BELOW THE TIDEMARK 



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many species are almost equally alert and voracious, and 

 chiefly differ in their methods of protecting themselves from 

 enemies. Some hide in the sea-weed fringing rocks, and 

 others in wet sand ; they sit in the sand with only their eyes 

 pricking the surface, or burrow into it hind part before, and 

 vanish almost as quickly as a sand-eel. The hermit crab, 

 which takes refuge in the cast-off shell of a mollusc, is 

 ingenious but degenerate. He has the birthright of a 

 nimble crustacean, but exchanges it for the clumsy protec- 

 tion of a snail-shell. This unworthy incubus hampers his 

 naturally active movements, and has constantly to be renewed 

 as he grows. 



