156 CRUSTACEANS. 



of a sultry summer's day induced me to put it outside the window of my • 

 study, in a capacious vessel of sea-water, where it remained during the 

 night, for all marine animals are benefited by the coolness of the atmo- 

 sphere. Next morning, when thinking little of the matter, I prepared to 

 replenish the vessel, a crab, lyuig on its back, struck my view, and beside 

 it one of rather larger dimensions, its very image. I hastily concluded 

 that a stranger had been introduced, — not at all an unlikely incident — 

 as here was a ready receptacle for any subject that might have arrived. 

 But exuviation had ensued in the night : the latter was the animal, 

 clothed in its new garb, and close beside it the former, now an empty 

 shell. 



Similar exuviations have repeatedly taken place. Yet the effect is 

 always so singular that I never behold it without astonishment. 



Specimens about to exuviate are usually dull, heavy, and inactive, 

 for a day or two preceding the change. I know not whether correctly, 

 but I have been led to conclude, that, for the most part, this incident be- 

 longs to the night, or early morning, whence, being very transient besides, 

 it is rarely witnessed. 



For a long time, having constantly found the old shell quite entire, 

 all the accessories and the minutest parts in their places, and all the 

 others in correspondence, bristles, antennae, eyes, exactly similar, I con- 

 cluded, not unnaturally, that they must have been encased in each other. 

 I could not conceive how by any other means, than the new gTowing 

 within the old, the conformity could be so precise, — thence, that on exu- 

 viation, each was withdraAvn as from a sheath or socket. 



My conjectures, however, have not been verified, and, I apprehend, 

 that I was indulging too many fallacies. 



The new animal, as I shall call it, escapes from the hind part of the 

 old shell, which gapes the whole length between the two hind legs, and 

 beyond them. — Plate XXXV. figs. 1, 2, 3, 4. Hence, the new organs 

 protrude, if I be not mistaken, in the same order as they stand in the old 

 shell, the hind legs first, and the claws being hberated the last. One 

 fact is indisputable, in the new shell being always larger than the old. 

 Many persons affirm, also, that it is soft, and that the crab, in its natural 



