THE THORNBACK CRAB. 563 
lously rapid, and how it can be accomplished, without subjecting the Crus- 
taceans to the lot of the starveling mouse, who crawled into a jar of corn, but 
could not crawl out again after 
feasting on its contents, seems 
to partake of the charater of an 
animated puzzle. 
The answer to the problem is 
simply that the creature sheds 
its armour annually, expands 
rapidly while yet covered only 
by a soft skin, and is soon pro- 
tected by a freshly-deposited 
coat of shelly substance. Even 
this answer contains a second 
problem little less difficult than 
that which it solves. How can 
a Crustacean, say a crab or a 
lobster, shed its skin? It is 
true that the cast shells are 
found, showing that the creature 
has escaped from its old and 
contracted tenement by a slit in 
some part of the body, such as 
the top of the carapace, and has 
left its shell in so perfect a 
COMMON THORNBACK CRAB.—(MJaza 
Squinado.) 
state that it might easily be mistaken for the living animal. 
But how did it manage about the claws? We all know what large mus- 
THORNBACK SPIDER-CRAB. 
cular masses they are, how very small is the aperture in which the joint 
works, and how stiff and firm is the broad tendinous plate which is found in 
their interior. Examination shows that there is no opening on the claws 
902 
