COMMON SHORE-CRAB, ETC. 99 



exuviae : even the singular dental apparatus, situated 

 in the stomach, is cast off and reformed; and yet, 

 how is all this accomplished 1 ? how do such parts 

 become detached? how are they renewed? We appre- 

 hend that more puzzling questions than these can 

 scarcely be propounded to the physiologist ; nor could 

 more interesting subjects of inquiry be pointed out to 

 those whose opportunities enable them to prosecute 

 researches connected with their elucidation." 



Another curious fact in connexion with these ani- 

 mals must not be omitted. This relates to the power 

 they possess of rejecting an injured limb. Upon the 

 occurrence of such an accident, a new limb is gradu- 

 ally developed, and remains folded up in the old 

 shell, ready to start forth sound and whole at the 

 next moulting-time ! 



To quote the words of Mr Spence Bates* "When 

 a limb is injured, all Crustacea have the power of re- 

 jecting it, except the wound be below the last joint. t 

 This is done by an apparently violent muscular con- 

 traction, finishing with a blow from another limb, or 

 against some foreign body. The amputation is the 

 work of a few seconds, except when they have but 

 recently cast the exuviae, when, during the first few 

 days (before the new skeleton is hardened), they have 

 not that easy capability, and the wounded limb will 



* "Mag. Nat. His. ,"1851. 



t I once cut the hand of a Crab through the joint, so as to 

 remove only the thumb and finger. The limb was not rejected. 

 When the shell was cast, the hand continued maimed, and never 

 was reproduced. 



