380 



HISTORY OF FISHES. 



kind, or hunting its prey ; it lies torpid and 

 motionless, as if in anxious expectation of the 

 approaching change. Just before casting its 

 shell, it throws itself upon its back, strikes its 



joint where the animal is itself accustomed to separate 

 it when injured, the usual membrane formed towards 

 the body, and no discharge took place ; but a watery 

 fluid proceeded copiously from the surface towards the 

 limb, which was thus soon left empty, speedily becomin 

 capable of being blown up with air like a bladder. On 

 proceeding to dissect the body a similar circumstance 

 took place, the fluid running off in so large a quantity, 

 that I regretted when too late, that I had not taken the 

 .precaution to have measured it. In a few minutes, the 

 body had so sunk into one mass that I was unable to 

 distinguish the separate parts. At the lower and inner 

 part of each joint of the chelae and legs, an opening re- 

 mained, in the form of a slit; through which the flat 

 central bony plate, found in the empty crust, had been 

 withdrawn ; which opening of course must be closed 

 when the shell is finally consolidated. 



It appears from close inspection, that the exuviae of a 

 lobster consists of the same parts as those of a crab ; the 

 whole internal skeleton and external surface of the 

 branchiae, with the osseous tendons of the muscles, hav- 

 ing been rejected. But they are more distinctly ascer- 

 tained in the latter species, from their greater firmness 

 of texture ; and I may add also in reference to myself, 

 that a desire to preserve the specimen perfect, had in 

 the former case prevented a very minute examination of 

 the internal structure. 



Having procured a crab that was beginning to show 

 signs of a commencement of the process of exuviation, 

 I found the limbs shrunk to three-fourths of what the shell 

 could well contain ; the soft contents of the points of the 

 chelae being diminished much more than the muscular 

 structure. A greater diminution than this, however, 

 takes place before the process of deliverance is accom- 

 plished ; but all the vigilance that I have exerted has 

 not enabled me to see the actual escape from the crust ; 

 which is usually left in some void place, often in a sandy 

 basin, and, as several fishermen have informed me, always 

 on its back ; as the living specimen I have described is 

 represented also to have been found in the store-pot. 



The newly extricated crab has at first strength enough 

 to crawl off to a place of safety, commonly beneath the 

 shelter of a neighbouring crevice, of such limited dimen- 

 sions at its entrance,, that it seems surprising it should 

 ever be able to return from it, in its new state of growth. 

 The first instinct of nature after securing a place of 

 retreat, is to absorb, I suppose by swallowing it, as much 

 fluid as will distend its organs and their common cover- 

 ing, now as flexible as velvet, to the full extent of their 

 capacity; by which means the deposition of crustaceous 

 particles is made according to the dimensions of its 

 newly acquired bulk: which in the instance now des- 

 cribed, that had arrived at the ordinary size of a female, 

 and allowing for the thickness of the first crust, exceeded 

 the former by at least an inch in its longest diameter, 

 and in all its dimensions in the same proportion. In 

 the early stages of growth, the increase of bulk at ex- 

 uviation is, of course, much more considerable, in rela- 

 tive proportion. Some of these smaller specimens may 

 be found passing through this natural process in every 

 month of the year ; but in some adult individuals, the 

 same crust must continue for a long time, since I have 

 seen one with oysters measuring two inches and a half 

 in length, on the carapace ; and in another, a mussel 

 (mytilus) about an inch in length, attached by its byssus 

 to a joint near the body. 



Whether, as has been said, the rejected case forms a 

 n.eal for its old inhabitant, on its first return to habits of 

 at tiviiy,ma.v wellbe questioned; though I have known 



claws against each other, and every limb 

 seems to tremble ; its feelers are agitated, and 

 the whole body is in violent motion ; it then 

 swells itself in an unusual manner, and at last 

 the shell is seen beginning to divide at its 

 junctures ; particularly, it opens at the junc- 

 tures of the belly, where, like a pair of jumps, 

 it was before but seemingly united. It also 

 seems turned inside out, and its stomach comes 

 away with its shell. After this, by the same 

 operation, it disengages itself of the claws, 

 which burst at the joints ; the animal, with a 

 tremulous motion, casting them off as a man 

 would kick off a boot that was too big for him. 



Thus, in a short time, this wonderful crea- 

 ture finds- itself at liberty, but in so weak and 

 enfeebled a state, that it continues for several 

 hours motionless. Indeed, so violent and 

 painful is the operation, that many of them 

 die under it; and those which survive are in 

 such a weakly state for some time, that they 

 neither take food nor venture from their re- 

 treats. Immediately after this change, they 

 have not only the softness but the timidity of 

 a worm. Every animal of the deep is then 

 a powerful enemy, which they can neither 

 escape nor oppose ; and this, in fact, is the time 

 when the dog-fish, the cod, and the ray, devour 

 them by hundreds. But this state of defence- 

 less imbecility continues for a very short time: 

 the animal, in less than two days, is seen to 

 have the skin that covered its body grown al- 

 most as hard as before ; its appetite is seen to 

 increase ; and, strange to behold ! the first ob- 

 ject that tempts its gluttony, is itsown stomach, 

 which it so lately was disengaged from. This 

 it devours with great eagerness ; and some time 

 after eats even its former shell. In about 

 forty-eight hours, in proportion to the animal's 

 health and strength, the new shell is perfectly 

 formed, and as hard as that which was but 

 just thrown aside. 



To contribute to the speedy growth of the 

 shell, it is supposed by some, that the lobster 

 is supplied with a very extraordinary concre- 

 tion within its body, that is converted into the 

 shelly substance. It is a chalky substance, 

 found in the lower part of the stomach of all 

 lobsters, improperly called crabs' eyes, and 



an instance where one crab has devoured another, leav- 

 ing nothing but the points of the legs, and a small por- 

 tion of the carapace ; but in the analogous instance of 

 a prawn, that had just thrown off its exuviae, I have 

 detected the source of the firmness of the new covering, 

 in the presence of small shell-fish in its stomach. Under 

 a lens, a minute trochus, perhaps the T. zizyphinus, and 

 some specimens of an oval bivalve, were distinguishable. 

 This is perhaps the only period of their lives when their 

 food is of this kind, but its nature cannot often be ascer- 

 tained, by the comminution it undergoes from the man- 

 ner in which it is devoured, when the jaws have attained 

 their firmness. From, two communications ly Mr Couch 

 in the Magazine of Zoology and Botany. 



