CRUSTACEA. 295 



white membrane, which presents at first a convex 

 surface : this gradually rises to a point, and is 

 found on examination to conceal the rudiment of 

 a new claw. At first this new claw enlarges 

 but slowly, as if collecting strength for the more 

 vigorous effort of expansion which afterwards 

 takes place. As it grows, the membrane is pushed 

 forwards, becoming thinner in proportion as it 

 is stretched ; till at length it gives way, and the 

 soft claw is exposed to view. The claw now 

 enlarges rapidly, and in a few days more acquires 

 a shell as hard as that which had preceded it. 

 Usually, however, it does not attain the same 

 size ; a circumstance which accounts for our 

 frequently meeting with lobsters and crabs which 

 have one claw much smaller than the other. 

 In the course of the subsequent castings, this 

 disparity gradually disappears. The same power 

 of restoration is found to reside in the legs, the 

 antennae, and the jaws. 



We must naturally be curious to learn, if pos- 

 sible, from what source these astonishing powers 

 of regeneration are derived. Reaumur hazarded 

 the conjecture, that there might be originally 

 implanted in each articulation a certain number 

 of embryo limbs, ready to be developed as occa- 

 sion might require; somewhat in the way in 

 which the rudiments of the secondary teeth 

 remain concealed in the jaw, in preparation for 

 replacing the first set when these have been re- 



