A STUDY OF BONES. 65 



like shape. As he never lives in the water, 

 he never feels the need of a tail. 



The edible crab and lobster show us an 

 exactly parallel case amongst crustaceans. 

 Everybody has noticed that a crab's body is 

 practically identical with a lobster's, only that 

 in the crab the body-segments are broad and 

 compact, while the tail, so conspicuous in its 

 kinsman, is here relatively small and tucked 

 away unobtrusively behind the legs. This 

 difference in construction depends entirely 

 upon the habits and manners of the two 

 races. The lobster lives among rocks and 

 ledges ; he uses his small legs but little for 

 locomotion, but he springs surprisingly fast 

 and far through the water by a single effort 

 of his powerful muscular tail. As to his big 

 fore-claws, those, we all know, are organs of 

 prehension and weapons of offence, not 

 pieces of locomotive mechanism. Hence the 

 edible and muscular part of a lobster is 

 chiefly to be found in the claws and tail, 

 the latter having naturally the firmest and 



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