CRUSTACEA. 327 



by various contortions of its body seems to be employed in 

 loosening thoroughly every part of its worn-out covering from 

 all connection with the recently secreted investment. This being 

 accomplished, it remains to extricate itself from its imprisonment ; 

 an operation of some difficulty ; and, when the nature of the ar- 

 mour to be removed is considered, we may well conceive that not 

 a little exertion will be required before its completion. As soon 

 as the old case of the cephalo-thorax has become quite detached 

 from the cutis by the interposition of the newly formed epidermic 

 layer, it is thrown off in one piece after great and violent exertion ; 

 the legs are then withdrawn from their cases after much strug- 

 gling ; and, to complete the process, the tail is ultimately by long- 

 continued efforts extricated from its calcareous covering, and the 

 entire coat of mail which previously defended the body is discarded 

 and left upon the sand. The phenomena which attend this reno- 

 vation of the external skeleton are so unimaginable, that it is 

 really extraordinary how little is accurately known concerning the 

 nature of the operation. The first question which presents itself 

 is, how are the limbs liberated from their confinement ? for, won- 

 derful as it may appear, the joints even of the massive chela of 

 the lobster do not separate from each other, but, notwithstanding 

 the great size of some of the segments of the claw, and the slender 

 dimensions of the joints that connect the different pieces, the 

 cast-off skeleton of the limb presents exactly the same appearance 

 as if it still encased the living member. The only way of ex- 

 plaining the circumstance, is to suppose that the individual pieces 

 of the skeleton, as well as the soft articulations connecting them, 

 split in a longitudinal direction, and that, after the abstraction 

 of the limb, the fissured parts close again with so much accuracy 

 that even the traces of the division are imperceptible. But this 

 is not the only part of the process which is calculated to excite our 

 astonishment : the internal calcareous septa from which the mus- 

 cles derive their origins, and the tendons whereby they are inserted 

 into the moveable portions of the outer shell, are likewise stated 

 to be found attached to the exuvise ; even the singular dental 

 apparatus situated in the stomach, of which we shall speak here- 

 after, is cast off and re-formed ! And yet, how is all this accom- 

 plished ? how do such parts become detached ? how are they 

 renewed ? We apprehend 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 



