204 VHILOSOPHICAL TRANSACTIONS. [aNNO 1746. 



weight. The difference of sex is very conspicuous, and they are very prolific ; 

 but he could procure no certain account of their way of coupling, nor in what 

 time they attained to full growth. 



Once a year, like the lobster, they lose or cast their shells. Against this ex- 

 traordinary change, they chuse a close and well-secured retreat in the cavities of 

 rocks, and under great stones : there they creep in, and wait, till by degrees the 

 parts are disengaged ; which is effected by withdrawing their legs from their old 

 shells, leaving them, and the upper part of their body-shell behind. In this 

 naked state they make a ver}' odd appearance, being an ill shapen lump of jelly- 

 like substance, which gradually hardens into a shell a size larger than the old one ; 

 for this is the way of growth appointed for this animal, and others of the crusta- 

 ceous species. But what is most surprising, this large species of crab has a power 

 in itself voluntarily to crack and break its own legs or claws, and drop them off. 

 The reproduction of the legs of craw-fish has been mentioned in the History of 

 the Royal Academy of Sciences, with some just remarks on the growth of these 

 creatures' shells ; but he knows not of any writer that has taken notice of this 

 strange event of the crab. ij 



Mr. Benjamin Cook, at Newport in the Isle of Wight, p.r.s. informed Mr. C. 

 of this marvellous property in the great crab ; but he could not comprehend it, 

 till he saw the experiment tried on two crabs ; then he was soon convinced of 

 the truth of the fact ; for in a few minutes the legs all dropped off one after an- 

 other. 



This the crab will do in any position ; but the easiest method is to lay it on its 

 back, and then take a pair of strong iron pincers, and break the shell, and bruise 

 the flesh of the 3d or 4th joint of its small leg : after it has received the hurt, 

 it bleeds, and gives signs of pain, by moving its leg from side to side ; but after- 

 wards holds it quite still, in a direct and natural position, without touching any 

 part of its body, or its other legs, with it. Then, on a sudden, with a gentle 

 crack, the wounded part of the leg drops off at the second joint, or internodium, 

 from its body ; just as one sees the neck of a retort separate, where it has been 

 heated by a red-hot iron ring, on the application of cold water. Tbe great legs 

 are cast off in the same manner, but are not so easily laid hold on as the small 

 ones. Those who have not seen this wonderful operation may reasonably con- 

 clude, that the leg is cast out of its joint or socket ; but it is quite otherwise ; for 

 it cracks and breaks off in the smoothest part of the joint, and the rim of the 

 body-shell is no ways assistant to it. 



To try what effect increase of pain would have in this work, a small hole was 

 pierced in the great legs, and then a pointed iron was put in to lacerate the in- 

 closed muscle : the consequence was answerable to expectation ; symptoms of 

 greater pain ensued, and the leg was cast off with greater violence. 



