ANCEUS. 183 
But we have not run the risk of such imputation, having 
carefully examined the structure of the female before 
the ova were developed, while they were in the ovisac, 
and after the presence of embryos in the ovi-pouch; we 
therefore think it possible that exceptions to a common 
law may exist in this as well as in other things. 
The ovi-pouch of this genus appears not formed by 
a series of fine scales attached to the coxa, as in the 
Amphipoda, but by a thin membrane, that is itself the 
wall of the ventral surface of the animal, which splits into 
scales when the embryo is ready to take its departure. 
M. Hesse states the period of incubation to be from 
twenty to twenty-five days, and sometimes less, and he 
believes that impregnation takes place prior to the last 
or adult moult of the animal. This is contrary to our 
anticipation, and, indeed, contrary to the common law of 
nature. We have certainly dissected adult animals that 
have not had the trace of ova. We therefore believe 
that immediately after the animal has undergone the 
adult moulting, it ceases from its gormandizing and com- 
mences breeding, and that, consequently, impregnation 
takes place immediately after the moult. 
Observers must have noticed that in the younger stage 
—that is, until the animal ceased to have a digestive ap- 
paratus—the animal, by feeding, distends the posterior 
portion of the pereion to a considerable extent, whence 
M. Hesse says that ‘‘ sometimes they are so gorged with 
blood that they become as distended as if they were full 
of eggs.” 
It must strike the physiologist as a remarkable cireum- 
stance, that the part which becomes distended by feeding 
is not the stomach, which in crustacea exists in the 
cephalon, but that part which afterwards becomes the 
reservoir of the future progeny. 
