THE SHEDDING OF THE SKIN, 35 
The operation is facilitated by the splitting of the old 
integument of the limb along one side longitudinally. 
When the legs are disengaged, the animal draws its 
head and limbs completely out of their former covering ; 
and, with a sudden spring forward, while it extends its 
abdomen, it extracts the latter, and leaves its old skele- 
ton behind. The carapace falls back into its ordinary 
position, and the longitudinal fissures of the sheaths of 
the limbs close up so accurately, that the shed integu- 
ment has just the appearance the animal had when the 
exuviation commenced. The cast exoskeleton is so like 
the crayfish itself, when the latter is at rest, that, except 
for the brighter colour of the latter, the two cannot be 
distinguished. 
After exuviation, the owner of the cast skin, ex- 
hausted by its violent struggles, which are not unfre- 
quently fatal, lies in a prostrate condition. Instead of 
being covered by a hard shell, its integument is soft and 
flabby, like wet paper; though Réaumur remarks, that 
if a crayfish is handled immediately after exuviation, its 
body feels hard; and he ascribes this to the violent con- 
traction which its muscles have undergone, leaving them 
in a state of cramp. In the absence of the hard skeleton, 
however, there is nothing to bring the contracted muscles 
at once back into position, and it must be some time 
before the pressure of the internal fluids is so distributed 
as to stretch them out. 
When the process of exuviation has proceeded so faa 
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