402 REPORT OF THE COMMISSIONER OF FISHERIES. 
to be a series of leaps, and the animal seems too far above the bottom 
to be running upon it; yet all the legs are in motion except the large 
first pair. Of the latter, the one on the side toward which the animal 
is moving is held straight out sidewise, while the other is folded up 
under the shell. 
METHOD OF CONCEALMENT. 
The coloration of the crab is suck as to harmonize very perfectly 
with the surroundings, and the animal attempts very little concealment 
if there are other objects on the bottom. Often, however, a clear, 
sandy bottom or some oozy pond will be found to be almost alive with 
crabs which have buried themselves until only, their eyes and their 
antenne are exposed. In thus hiding, the crab goes nearly vertically 
backward into the bottom and then, by a few movements, turns 
slightly, so that the shell rests at an angle of about 45°. The material 
above settles down and effaces all traces of the entrance. It usually 
happens that the bottom affected. by the crab is firm enough to render 
this operation somewhat slow and it rarely attempts to escape pursuit in 
such a way. It seems probable that concealment is usually adopted as 
an ambush from which a sudden attack can be made on some passing 
fish. 
In certain places, notably shallow ponds and streams which become 
nearly dry at low tide, the crab may be observed to dig rather large, 
conical holes, apparantly as reservoirs, and to take up its position in 
the deepest part. The work of making such an excavation often 
requires two or three hours, usually commencing soon after the tide 
has begun to ebb strongly and continuing until the edge of the exca- 
ration is nearly exposed above the water. The animal works from 
some suitable point, carrying away load after load of material clasped 
between the large claw and the lower surface of the front of the shell. 
It loosens up the surface with the tips of its second, third, and fourth 
pairs of legs, grasps all it can carry, and then moves off a few inches in 
the direction of the side which bears the load and deposits it so that it 
will not roll back. Thus the hole is gradually deepened and the sur- 
rounding circle built up and widened until it has a breadth of about 
a foot, with a depth of perhaps 6 inches. The crab then settles 
itself into the sand or mud at the bottom of the hole and waits until 
the rising tide offers an opportunity to move about again. 
The blue crab has very seldom been seen to come out on land volun- 
tarily, although it is able to systain life for several hours when 
removed from the water. In low, swampy situations I have occasion- 
ally seen an individual moving about in the dense grass or hanging to 
the grass just above the water, and in Miss Rathbun’s paper ‘* The 
Genus Callinectes,” there is a description by Mr. Willard Nye, jr., of 
the migration of a large number of crabs from a-small pond to the 
