328 



HISTORY OF FISHES. 



descend to be excluded, and placed under the 

 tail, where the animal preserves them from 

 danger for some time, until they come to ma- 

 turity ; when, being furnished with limbs and 

 motion, they drop off into the water. 



When the young lobsters leave the parent, 

 they immediately seek for refuge in the 

 smallest clefts of rocks, and in such like cre- 

 vices at the bottom of the sea, where the 

 entrance is but small, and the opening can be 

 easily defended. There, without seeming to 

 take any food, they grow larger in a few 

 weeks' time, from the mere accidental sub- 

 stances which the water washes to their 

 retreats. By this time, also, they acquire a 

 hard firm shell, which furnishes them with 

 both offensive and defensive armour. They 

 then begin to issue from their fortresses, and 

 boldly creep along the bottom, in hopes of 

 meeting with more diminutive plunder. The 

 spawn of fish, the smaller animals of their 

 own kind, but chiefly the worms that keep at 

 the bottom of the sea, supply them with 

 plenty. They keep in this manner close 

 among the rocks, busily employed in scratch- 

 ing up the sand with their claws for worms, 

 or surprising such heedless animals as fall 

 within their grasp : thus they have little to 

 apprehend, except from each other ; for in 

 them, as among fishes, the large are the most 

 formidable of all other enemies to the small. 



But this life of abundance and security is 

 soon to have a most dangerous interruption ; 

 for the body of the lobster still continuing to 

 increase, while its shell remains unalterably 

 the same, the animal becomes too large for its 

 habitation, and, imprisoned within the crust 

 that it has naturally gathered round it, there 

 comes on a necessity of getting free. The 

 young of this kind, therefore, that grow faster, 

 as I am assured by the fishermen, change their 

 shell oftener than the old, who come to their 

 full growth, and who remain in the same 

 shell often for two years together. In general 

 however, all these animals change their shell 

 once a-year ; and this is not only a most pain- 

 ful operation, but also subjects them to every 



dan 



er. 



Moulting season is generally about 



1 Process of Exuviation in Shrimps, Lobsters, and 

 Crabs. Dr Milne Edwards, in his Histoire Naturelle 

 des Crustaces, has given an account of what may be 

 considered the present state of our knowledge, of the 

 rircumstanc.es under which the process of exuviation is 

 effected, and the methods by which it is accomplished 

 in the long-tailed stalk-eyed crustaceans ; but as much 

 of what that eminent naturalist advances is derived from 

 other authorities, and I have reason to conclude, con- 

 trary to the general opinion, that the circumstances 

 amending this process of nature, are different in even 

 nearly allied species, there still remains space for inquiry. 



Reaumur is our only original authority for the minute 

 rir-umstances attending the process of exuviation, which 

 he observed in the river crayfish (Potamohius flnviatilis, 

 Leach ,) but not having an opportunity of consulting 



the beginning of summer, at which time their 

 food is in plenty, and their strength and vigour 

 in the highest perfection. But soon all their 

 activity ceases ; they are seen forsaking the 



that author's work, I copy his narrative from Dr M. 

 Edwards's quotation: A few days previous to the 

 commencement of the operations, the creature abstains 

 from all solid nourishment, and the carapace and abdo- 

 minal segments will be found to offer less than the usual 

 resistance to the pressure of the finger. Shortly after- 

 wards the crayfish appears restless, and rubs its legs 

 against each other; it then throws itself on its back, 

 agitates its whole body and then distends it, by which 

 the membrane joining the carapace to the abdomen is 

 burst, and this great dorsal plate is raised. Some degree 

 of rest follows these first struggles ; but after a short time 

 the animal again puts all its organs in motion, the ca- 

 rapace is seen to rise gradually from the legs beneath, 

 and in less than half an hour, the animal has extricated 

 itself from this portion of its slough. By retracting its 

 head, the antennae, eyes, and legs are withdrawn as from 

 a case ; and the extrication of the last, being the most 

 difficult and complicated operation, is attended with so 

 much pain, that the effort sometimes occasions the loss 

 of one or more of the organs. The hinder parts are 

 withdrawn with less difficulty; the head is conducted 

 below the carapace, and the tail being thrown off by a 

 forward motion attended with a brisk and distensive 

 action, the creature is seen divested of all its encum- 

 brances, and the case is left unbroken, as il no struggle 

 had ever taken place within it. 



I have no doubt that the process here described in the 

 cray-fish corresponds to what takes place in the common 

 prawn (Palsemon serratus, Leach,) although I have never 

 been able to observe it in operation : the following is 

 a description of the rase from which the animal has 

 recently extricated itself : The whole is thin, elastic and 

 transparent ; the carapace with its serrated process whole, 

 the antennae perfect to their minute extremities: the 

 palpi and jaws drawn within the cavity of the thorax, 

 and partially separated from the sternal plate ; the latter 

 with the legs still forming a loose attachment to each 

 other, and without fracture, but drawn somewhat pos- 

 teriorly into the thoracic cavity. The case and pedestal 

 of one eye \vere within the thorax, but the other could 

 not be found; the legs perfect, and attached to the 

 sternal plate. The caudal plates were united at their 

 joints, but in no part was there any intervening mem- 

 brane, this portion of the body not appearing to be 

 thrown off with the more solid covering: a circumstance 

 which will account for the fact, that the eyes do not long 

 remain attached to the adjacent parts after the slough is 

 left by its inhabitant. 



The habits of the lobster (Astacus Europeus, Leach,) 

 at this periodical crisis, and the circumstances attending 

 it, present a very considerable difference from those of 

 the species already mentioned. So far from abstaining 

 from food, it is not uncommon for it to be taken in crab 

 pots, which it has been enticed to enter by the allure, 

 ment of the usual bait; and instances have been related 

 to me, where, when the fishermen commenced to handle 

 his capture, the animal has slipped away, leaving an 

 empty husk as the only reward of his labour. It was by 

 a circumstance somewhat similar that the opportunity is 

 afforded me of giving a minute description of a very per- 

 fect case, left by the creature when it made its escape: 



for escape it did, through an aperture too narrow to 



have allowed it to pass if its new covering had possessed a 

 very moderate degree of firmness to the no small 

 annoyance of the fisherman, who had calculated on the 

 possession of a prize somewhat, above the ordinary mag- 

 nitude. I cannot find that any extraordinary actions or 

 contortions have been observed in the lobster, whcrt 



