154 
MARINE FAUNA OF ST. ANDREWS. 
circumstances the body is coated with mud, which tills up the 
irregularities of its conformation, and loads the abdominal 
feet and hairs ; yet the crab is vigorous and healthy, and out¬ 
lives sanitary apprehensions. 
Under almost every stone within reach of the tide young 
specimens occur. At low water the full-grown crabs seek the 
hiding-places just mentioned, or shade themselves under the 
blades of the seaweeds in the rock-pools. Occasionally one is 
found adhering to the soft body of a moulting brother and, 
cannibal-like, devouring the branchiae, new carapace, and other 
soft organs with savage pertinacity, while the old shell has 
not quite fallen from its victim. Moulting shore-crabs are 
generally found alone, as if aware of their helplessness, 
and dreading, with some degree of justice, the voracity of 
enemies and even unscrupulous relations. Very slight injury 
kills them in this condition ; and of course, for a time, they are 
incapable of defending themselves from even weak assailants. 
The shore-crab is found in pools at the East Rocks where no 
other marine articulate of the same class occurs, and the water 
cannot but be brackish, since the pools are not filled by ordinary 
tides, and fresh streams from the crags flow in the neighbour¬ 
hood. In these resorts the colour of the crab is not so pretty, 
being of a muddy green with pale limbs; and the specimens 
in the highest pools are generally small. It is not surprising, 
however, to find them in such places, after watching their 
activity in the innumerable brackish lakes of the Outer 
Hebrides, and their evident comfort in perambulating the 
muddy flats even where streams of fresh water abound. 
On land, Carcinus mcenas is, perhaps, the most active British 
crab, especially in regard to offence, defence, and escape. It 
scrambles over the rugged rocks with astonishing speed, while 
defending itself with its uplifted chela?; and so fierce is it in 
attack, that, having once seized an object with the latter, the 
spasmodic effort is sometimes so great that the limb separates 
from the trunk at the base. The males frequently engage in 
combat; and a fatal issue would more frequently ensue, were it 
not for the provision whereby haemorrhage is speedily arrested 
and the lost portion repaired or reproduced. Few specimens, 
indeed, are quite free from injury. Some have recently repaired 
wounds of the carapace (Plate IX. fig. 12) ; others have lost 
