But only two or three days later those very same crabs—with branded carapaces—were caught anew by the fishermen; not near Falmouth, but as before, off the Lizard. How they had managed to get there, how they had first found their way to Falmouth Harbour, a distance of four miles, and then for miles more along the coast, are questions more easily put than answered. The word “instinct” fails to meet the difficulty.
One thing only is clear, that they preferred the neighbourhood to which they were accustomed.
Very fearless creatures are small crabs, generally; brave, no doubt, partly because of their numbers.
In nets and trawls, where animals of many kinds are together for long hours of captivity, the weak are often destroyed by the strong, before they can be drawn up.
But sometimes the weak combine together, and prove too much for the strong. Notably this was the case, when a dog-fish, brought up from a depth of over fourteen hundred fathoms, was entirely disposed of in twenty hours by crowds of hungry little crustaceans.
Most of the crabs and lobsters, shrimps and prawns, which live on or near the bottom, send their young ones up into higher levels for education. There for a while the juveniles swim and develop, till old enough in their turn to take to the ocean-bed. Great numbers have meanwhile been preyed upon by multitudes of fishes in those upper levels.
Crabs undergo curious changes in the course of their growth from infancy to adult age. At certain stages they are so utterly unlike in appearance to what they become later, that for a long while they were classed by naturalists under separate names, being actually reckoned as different creatures.
Since the protecting armour of a crab is far too rigid to admit of its stretching, it becomes from time to time too tight for the growing body within. When it can no longer be endured, it has to be cast off, and a new suit, larger in size, has to form in its place.
This armour, like the shells of foraminifers, and the skeletons of coral-polyps, is unconsciously secreted by the crab; and during the formation of a new suit of armour the crab has a time of weakness, of delicate health, and also of dangerous exposure to the attacks of enemies.
Some kinds of crabs have sunk to the miserable level of parasites, living on the exertions of others, and refusing to exert themselves. One prefers to think of the active and independent and intelligent kinds; and really, crabs have a good deal of intelligence. Quite as much as an average insect; though perhaps few of them could compete in an examination with ants or bees.