shelly integument envelops them from their earliest youth, and as it
does not expand and grow, the natural growth of the soft body beneath
would be entirely prevented did not nature supply a remedy of a very
curious kind--the exuviation, or periodical throwing off of the
external crust, and the formation of a larger shell-covering fitted
for the increasing growth of the animal. This is a circumstance which
has long been familiar to naturalists, and indeed the most ordinary
observer must have often remarked in the crabs and lobsters brought to
table, appearances indicative of their change of external coverings.
In the back of the edible crab, may often be noticed a red membrane
lining the inner side of the shell, but so loose as to be readily
detached. Along the greater part of its course this membrane has
already assumed a half-crustaceous consistence, and is just the
preparatory process to the old shell being thrown off by the animal.
There is another curious circumstance which has also been long
known--that crabs and lobsters can renew lost limbs. Some
misconception, however, had existed regarding the manner in which this
was effected, until the observations of the late Sir John Dalyell have
thrown more accurate light on the subject.

This most amiable and eminent zoologist, who was lost to science last
year, afforded a pleasing illustration of the solace and delight which
the pursuit of the study of nature yields to the diligent inquirer
into her mysteries. With a feeble constitution and frame of body,
which precluded his mingling in the more active pursuits of everyday
life, this sedentary philosopher collected around him examples of
minute and curious being from the depths of the ocean, from lake and
river, and for many long years found the delight of his leisure hours
in watching the habits of the animals, and in discovering and
describing many singular circumstances in the constitution of their