THE AMERICAN LOBSTER. 
87 
repeated by Eymer Jones (106) and others. It is, without doubt, erroneous, but 
possibly based originally upon an exceptional occurrence. 
At the time of the casting of the shell the large claws must be practically free 
from blood, since, as Vitzou has pointed out, if the claw were to be increased in size 
it would be next to impossible for it to be withdrawn without rupture. The older 
naturalists used to explain the withdrawal of the large claws by a wasting of the 
tissues. The lobster was supposed to become sick and emaciated, which, of course, 
was an error. The most significant fact in this process is the displacement of the 
liquids which normally belong to these appendages. 
Couch (47), in his account of the exuviation of the common edible crab of Great 
Britain, Cancer pagurus , maintains that the membranes in the areas of absorption at 
the base of the chelipeds split along the edges and open like hinges, thus freeing 
the limb from its constraint. This does not happen in the lobster, as Couch inferred, 
and even if it did no benefit would arise, since there is the unbroken ring of the 
coxopodite, through which the tissues must still pass. Spence Bate (10) thought that 
the splitting of the walls of the cheliped, alluded to by Couch, might be to enable “the 
animal to withdraw the great osseous tendon.” It is difficult to understand what is 
here meant. The great osseous tendons are never withdrawn at all (past the absorp- 
tion areas at the base of the limb), but remain attached to the old shell, of which they 
form a part. 
THE CAST-OFF SHELL. 
At the time of the molt there is an intermediate membrane which makes its 
appearance between the new and old shells. It is non-cellular, has a gelatinous appear- 
ance, is very transparent, and may be found adherent to the old shell after the molt is 
past. When examined microscopically it has the appearance shown in fig. 177, pi. 44. 
It bears the impress of a mosaic of cells, which can be uone other than the cells of the 
chitinogenous epithelium. Vitzou is thus in error in supposing that this substance is 
a secretion of the chitinogenous epithelium underlying the new carapace, which it 
traverses by endosmosis. It must be either the first secreted product of the new shell 
or the innermost layer of the old shell modified by absorption. 
In this cuticular membrane the parts which correspond to the cell boundaries (of 
the chitinogenous epithelium) have the form of elevated ridges on the under side, and 
in the center of each polygonal area there is a slight thickening. Eeaumur (162) had 
in view a similar structure in the crayfish when he spoke of a glairy matter, “as» 
transparent as water, which separated the parts which the crayfish was soon to 
cast off from the rest of the body, and which allowed these to glide smoothly over one 
another.” 
There is normally no rupturing of the shell in any part in the course of the molt. 
The entire exoskeleton, with the linings of the oesophagus, stomach, and intestine, 
comes oft' as a whole, 1 and the animal leaves it by drawing the anterior parts of the 
body backward, and the abdomen and its appendages forward, through an opening- 
made by the elevation of the carapace. When the old carapace falls back into its 
1 The lining of the alimentary tract is of course ruptured. In small lobsters, at the fifth or sixth 
molt, I have noticed that the break takes place not far behind the stomach-bag, and that while the 
linings of the masticatory stomach and oesophagus come out by way of the mouth, as in the adult, the 
lining of the intestine is withdrawn from the anus. 
