EECEEATIYE SCIENCE. 



97 



like filameuts, is also cast off, togetlier witli 

 the cornea of the eye, and the lining of the 

 stomach, with its strong grinding teeth, which 

 some of our readers have, no doubt, heard 

 called " the lady in the lobster." The crus- 

 tacean, now denuded, remains a soft, defence- 

 less mass, invested merely with a thin pellicle. 



Various species have their own mode of 

 effecting this exuviation, and their own diffi- 

 culties to contend with, for the operation is 

 not in all cases very easy. Some difference 

 in this respect may not improbably depend 

 upon the age or condition of the individual, 

 or upon causes beyond our present knowledge. 



It is at this crisis, when the creature is 

 soft and clad in a delicate pellicle, that its 

 growth and general expansion take place ; and 

 this increase of bulk appears to proceed with 

 remarkable celerity, a degree of suddenness, 

 as if the pent-up frame, ready in its confine- 

 ment for a sudden and energetic process of 

 development, waited only the bursting of its 

 wall of durance. 



Every species, as we have said, presents 

 us with its own mode of exuviation ; for the 

 process is definite, and not irregular or as 

 the chance may be. The seasons also of 

 this change are to a great extent determi- 

 nate, though exuviation may be hastened or 

 retarded by circumstances, or altogether sus- 

 pended, even before the normal stature is 

 attained. Then of course no further moult 

 takes place, the animal having attained its 

 maximum of development. 



The armour being thus thrown off, and 

 the soft pellicle-covered body having en- 

 larged, the secretion of a new coat of mail 

 from the surface of the pellicle commences 

 and is speedily completed ; the antennae 

 being again sheathed, the eyes fitted with 

 new glasses, and the stomach relined and 

 furnished with a new grinding apparatus. 



It is supposed that crabs, lobsters, and 

 crayfish undergo this change annually ; but 

 abundance of food and congeniality of tem- 

 perature, or the contrary, have, undoubtedly. 



much influence in hastening or retarding it. 

 "We have every reason to believe that the 

 exuviation of shrimps and prawns is very fre- 

 quent, at least during the first period of their 

 active existence, and it would appear that 

 this is also the case with the young of crabs 

 and lobsters, the intervals being longer as 

 maturity approaches. Perhaps a brief ac- 

 count of the mode of exuviation in two spe- 

 cies, the common lobster and crab, may be 

 here admissible. Up to the time of its moult 

 the lobster is active and vigorous, and con 

 trary to what has been observed by E-eaumur 

 in the river crayfish or crawfish (which effects 

 its freedom not without great struggles and 

 contortions), it is agitated by no violent 

 actions or convulsive efforts ; nay, so easy is 

 the change that fine specimens, in the hands 

 of the fisherman, have suddenly slipped from 

 their encasement, leaving only their shell as 

 the reward of his labour. 



It was by a circumstance of this nature 

 that Mr. Couch was afforded the opportunity 

 of witnessing the process and obtaining a 

 perfect case left by the creature when it 

 made its escape — for escape it did, to the 

 no small annoyance of the fisherman, who 

 was congratulating himself on a prize. 



In the specimen thus obtained by Mr. 

 Couch, the sheathing of the antennae (horns) 

 and complicated appendages round the 

 mouth, the eye^stalks, and the transparent 

 cornesB were uninjured. The segments and 

 joints of the posterior or tail portion of the 

 body, with the caudal or terminating plates, 

 were all joined together, but without any 

 intervening membrane ; while the under parts 

 from beneath the snout, including the jaws, 

 foot-jaws, great claws, and legs, with the 

 breastplate, gullet or oesophagus, and inter- 

 nal coat of the stomach, formed one connected 

 portion. The manner in which the animal 

 escaped was not to be mistaken. " Through 

 the middle of the carapace (backplate) ran 

 a luie as straight as if it had been cut with 

 a knife, and evidently formed by a natural 



