6 
HISTORY OF BRITISH CRUSTACEA. 
beneath the membrane of the scar ; this remains in a soft 
state until the Crab again casts its shell, when the new 
claw is set at liberty, is straightened out, and becomes hard 
and calcareous like other parts of the body; so that a claw, 
instead of being renewed and perfected at once, or at the 
first casting of the shell, is not so in reality until the shell 
has been cast the second time.” Were a similar process to 
take place before the eyes of any one on a creature as bulky, 
say, as a buffalo, no flight of the imagination could conceive 
of anything more marvellous ; and yet it is a common occur- 
rence, one of the works of Him whose ways and name are 
Wonderful. 
"From the observations of the late Sir John Dalyell, pub- 
lished in the Report of the British Association for 1851, 
we may state that Crustacea begin to throw off their shells 
even in the embryo state in which they first appear after 
having left the egg. After every change they assume more 
and more of their perfect form. While the Crab is young, 
and growing rapidly, frequent exuviations occur at brief in- 
tervals, from three to five in the course of a year. Just 
before the change the animal almost ceases to feed, and 
becomes rather inactive; when the process has commenced 
it is effected in the course of a few hours, body and limbs 
