He placed the crab in a basin of water, which contained a supply of green sea-weed. And next morning a change was seen. The crab had cast aside his red ribbons, and had decked himself out with a smart array of green ribbons instead. Such conduct may, if we choose, be accounted for by the magic word “instinct;” but it certainly wears the aspect of deliberate intention, and even of some dim consciousness of cause and effect, not to speak of a knowledge of colour. This habit of the spider-crab is now well known and recognised; and he has been closely watched during the “dressing” process. It has been noted that he always puts each slip of sea-weed or scrap of sponge, or aught else that he uses for the purpose, to his mouth, before fastening it to his body or limbs. A suggestion has been made that his object in so doing is to lick it and render it sticky. Perhaps in some cases it could not otherwise be attached; but many of the spider-crabs have hooked hairs, exactly adapted for holding fast such objects as they love to adorn themselves with. Nor are the adornments always merely stuck on. Both sea-weeds and sponges frequently take root, and flourish as healthy growths upon the crab’s back. It is an extraordinary fact that the crabs seem to know perfectly well from which kinds of sea-weed or zoophyte they may snip off little bits, with a prospect of not killing them. So unerring, indeed, is their knowledge in this respect, that, as an authority on the subject has stated, “the keepers of Aquaria have only to consult the crabs to learn what kinds of sea-animals will bear being thus transplanted piecemeal.”[9] [9] _Crustacea_, by STEBBING. Is this too merely “instinct”? Many a time baits were lowered in the nets of the _Challenger_ to attract victims. Oddly enough, it was found that no more effective bait could be used for crabs and their kindred than--pieces of looking-glass! May one imagine that some friendly Medusa lent her little glimmer, far below, to enable the Hermit-crabs, when putting on fresh ribbons, to see their reflections, and judge of the effect? It reads rather like a page of _Alice in Wonderland_. Hermit-crabs or Soldier-crabs, having an insufficient protective armour of their own, are in the habit of using empty Mollusc shells to shelter that part of their bodies which is not guarded. One of these crabs, when young, chooses a shell, fitted to its size; and when grown too large for it, that shell is discarded in favour of a new one. But whether the said crab commonly contents himself with an empty habitation, the occupant of which has died earlier, or whether he first kills and eats the live Mollusc, and then “commandeers” the shell, does not seem to be known with certainty. CHAPTER XXII. THE WORLD OF FISHES “He giveth food to all flesh.”--Ps. cxxxvi. “Which giveth food to the hungry.”--Ps. cxlvi. 7.