FREQUENCY OF EXUVIATION. 125 



possible that the transparent case could by any pos- 

 sibility have held it. The mystery vanishes if the 

 new limb or claw be examined ; for, although in 

 shape it is perfect, even to the most minute parti- 

 cular, it remains for a certain period comparatively 

 useless to the animal, from the fact of its being 

 utterly devoid of flesh. 



The new limb, therefore, can be considered merely 

 as an expanded case, which, by a wonderful law of 

 nature, becomes slowly filled up and completed. 

 Immediately after exuviation has taken place, and a 

 claw is introduced in the place of some mutilated 

 stump, if any one will pull off the new member, he 

 can readily confirm the truth of what I have stated, 

 and, moreover, be able to test into how very small 

 bulk the new limb may be rolled. 



As the reader may remember, Goldsmith states 

 that the crab casts its shell 'regularly once a-year, 

 at the beginning of May.' Professor Owen fixes the 

 date in the month of August. Professor Bell states, 

 that 'there is no doubt exuviation takes place 

 annually with great regularity, until the growth is 

 completed, which, in many species, is not before the 

 animal is many years old/ Another professor, treat- 

 ing on the same subject, thus writes, ' We are told 

 that all this coat of mail is annually thrown off in 

 a single piece by the contained animal, the great 

 proficient in Chinese puzzles may well be posed at 

 this greater puzzle/ In fact, all writers whose works 



