892 Something about Crabs. 
Through the opening thus afforded the crab now withdraws him- 
self, coming forth a soft-shelled, weak, flabby creature. Now he 
is a pitiable object. The claws, which before could pinch so 
sharply, are now limp asa rag. His meanest enemy would now 
find him an easy victim, utterly incapable of the slightest defence. 
On account of this unprotected condition immediately after molting, 
all of the Crustacea seek some sheltered spot when about to cast 
their skin, and hence the operation is not often seen. ‘The process 
has its differences in the different species; thus the shell of the 
lobster splits down the middle of the back, while that of the horse- 
shoe crab splits around the sharp front edge, so as to afford the 
opening through which the animal is to emerge. 
There are, however, other processes which precede the splitting 
of the shell, which need to be mentioned, and which, as they have 
been most studied in the lobster, will be described as they occur 
there. First a word as to the nature of the shell. It is what is 
called a cuticular product. That is, it is not composed of cells like 
the rest of the body, or like the skin of man, but of a peculiar 
substance secreted by tle cells lying beneath. Its density in 
various species differs not only with the thickness of this layer, but 
as well with the amount of carbonate and phosphate of lime which 
is deposited in it. It is this outer non-cellular layer which is cast 
at each molt, while the cells secrete a new shell. If one examines 
closely any crustacean they will see (more numerous and larger m 
some places) that all over the body there are small hairs, but these 
hairs differ from those of man in that they consist of the same 
cuticle as the rest.of the body, and have an axis cylinder which 
arises from the cell beneath. It may also be said that these same 
hairs are organs of sense. One of the first preparations for a molt 
is the formation of new hairs and a new cuticle beneath the old 
one, and these new hairs have to lift and tear away the shell from 
the underlying shell. It is an interesting fact that in certain rep- 
tiles which “shed their skin,” there are bristles which lift the old 
integument in the same way. Another feature to be noticed is the 
way in which the lobster withdraws its big claw, and probably the 
same is true of the fiddler, though this is mere surmise. He 
examine a lobster we find that the pincer is much larger than the 
joints which connect it with the body, and it seems impossible that 
