298 LIST OF ENTOMOLOGICAL M'ORKS, 



subject, induces us to transcribe the passage even at the risk 

 of being charged with the repetition of an oft-told tale. One 

 word on the previous quotation : the fact that it is essential 

 for the Gecarcinus carnifex to pass its first days in the water, 

 clearly proves the young of that species have a different 

 economy from the adults. This fact establishes a metamor- 

 phosis almost as decisively as the detection of the young under 

 a totally different shape. 



In the spring, in boxes pierced with holes, which he placed both 

 in the river and in an apartment, Reavnnur put the fresh-water 

 cray-fish {Astacus fluviatilis). He observed, that when one of 

 these was about to cast its crust, it rubbed its feet one against the 

 other, and gave itself violent contortions. After these preparatory 

 movements it swelled out its body more than usual, and the first 

 segment of its abdomen appeared more than commonly distant from 

 the thorax. The membrane that united them now burst, and its 

 new body appeared. After resting for some time, it recommenced 

 agitating its legs and other parts, swelling to the utmost the parts 

 covered by the thorax, which was thus elevated and separated from 

 the base of the legs ; the membrane which united it to the underside 

 of the body burst asunder, and it only remained attached towards 

 the mouth. In a few minutes from this time the animal was 

 entirely stripped, except the legs. First, the margin of the thorax 

 was seen to separate from the first pair of legs : at that instant 

 drawing back its head, after reiterated efforts, it disengaged its eyes 

 from their cases, and all the other organs of the anterior part of the 

 head. It next uncased one of its fore-legs, or all or part of the legs 

 on one side, which operation is so difficult, that young ones some- 

 times die under it. When the legs are disengaged, the animal casts 

 off the thorax, extends the tail briskly, and pushes off its covering 

 and that of its parts. After this last action, which requires the 

 utmost exertion of its remaining vigour, it sinks into a state of 

 great weakness. Its limbs are so soft that they bend like a piece of 

 wet paper ; but if the back is felt its flesh appears unexpectedly 

 firm ; a circumstance arising, perhaps, from the convulsive state of 

 the muscles. When the thorax is once disengaged, and the animal 

 has begun to extricate its legs, nothing can stop its progress. 

 Reaumur often took them out of the water with the intention of 

 preserving them half uncased ; but they finished, in spite of him, 

 their moult in his hands. Upon examining the exuviae of these 

 animals, we find no external part wanting : every hair is a case 

 which covers another hair. The lower articulations of the legs 



