404 EEPORT OF THE COMMISSIONER OF FISHERIES. 



the complicated set of teeth in the stomach reduce it to a thin fluid 

 mass before it is allowed to pass into the intestine. 



Digestion in the crab seems to be a rapid process, for the food dis- 

 appears so quickly from the stomach that this organ is usually found 

 to be perfectly empty within a few minutes after having received a 

 full meal. It is a common idea among the fishermen that food is not 

 retained in the crab's stomach at all, but this I have disproved by 

 numerous dissections. 



REPRODUCTION. 



The sexes of the crab are separate, and reproduction is efl'ected by 

 means of eggs, which are laid by the female after copulation. The male 

 crab ma}' instantly be recognized by its narrow l-shaped aljdomen, or 

 apron, which is folded under the cephalo-thorax and lies over a rather 

 deep groove in the sternum between the second, third, and fourth pairs 

 of legs. (Fig. 2, pi. I.) Its base is broad and nearly fills the space 

 between the fifth pair of legs. The verges, or intromittent organs, 

 consisting of the much modified first pair of abdominal appendages, lie 

 withiiL.the sternal groove and are ordinarily completely hidden by the 

 abdomen, but are easily exposed b}^ raising that portion of the animal's 

 bod3\ The male is also usually distinguishable by its larger size and 

 the greater amount of blue on its legs and the lower surface of the 

 body. The soft-shelled male shows a good deal of blue on the back also, 

 but as the shell hardens this gives way to the usual dull gray green. 



Among the female crabs two distinct forms are recognizable, which 

 we may designate, respective!}', as virgin and ovigerous forms. In 

 both the body is more tumid and the abdomen is much broader than in the 

 male. In the virgin form the abdomen has a triangular shape, the sides 

 converging nearly uniformly from the base to the tip. (Fig. 3, pi. ii.) 

 In the ovigerous form it is nearly semicircular in outline, except for 

 the small terminal segment, which projects in front as a small triangle 

 on the middle line. (Fig. 4, pi. ii.) In the virgin form the abdomen 

 lies, as in the male, in a depression between the bases of the last four 

 pairs of legs, but it is fastened in its place so strongly, by means of 

 a pair of hooks which project from the body and fit into a pocket on 

 each side of the abdomen, that it can hardly be raised without being 

 broken. The swimmerets on such an abdomen are small — almost rudi- 

 mentary — and would hardly be noticed in a cursory examination. In 

 the ovigerous form, on the other hand, the abdomen covers nearly the 

 whole lower surface of-the shell, even overlapping the basal segments 

 of the last four pairs of legs, and it is held in position only by a nuis- 

 cular eftort on the part of the animal. When such an abdomen is 

 lifted up, the observer is at once struck with the large size of the 

 swimmerets, which, with their fringes of hairs, entirely fill the space 

 between the abdomen and the shell of the bod3^ It will further be 



