Page:The Zoologist, 4th series, vol 3 (1899).djvu/566

536 Othonia gracilis, and crusting colonies of Bryozoa protruding ever and anon circlets of hair-like tentacles." Hence, when the hairy H. fascigera is at rest on such a weed, the mimetic adaptation is greatly accentuated. Thus also the connection of the small Short-tailed Crab (Nautilograpsus minutus), which swarms on the Gulf-weed, and assimilates in colour thereto. Sir John Murray, during the voyage of the 'Challenger,' studied the habits of these Crabs. He observed "that, although every floating thing upon the surface is covered with them, they are rarely met with swimming free, and that whenever they are dislodged and removed a little way from their resting place they immediately make the most vigorous efforts to regain it." The Common Shrimp (Crangon vulgaris), when suspecting danger, "sinks upon the sand, and, setting his swimming-feet rapidly to work, they 'kick up such a dust' in the water that he is hidden in a cloud of fine sand, which as quickly settles down and partially buries him—sufficiently so with his sandy hue to effectually hide him." Mr. W.A. Lloyd has described a somewhat similar habit of the Echinus or Sea-urchin. "Its chief delight, when in an aquarium, appears to be to cover itself with pebbles, which it picks up with its spines. At first I imagined that the little stones had fallen by mistake, and, wishing to do all in my power to render my captive happy, I removed the pebbles with a brush; but the Sea-urchin evidently did not appreciate my would-be kindness, for in a short space of time he had again covered himself with pebbles; and so completely was he hidden beneath them, that if he had not crawled up the side of the aquarium with his load I should have had some difficulty in discovering his whereabouts." Some species of Crabs, such as Maja verrucosa, Pisa tetradon and P. armata, Inachus scorpioides, and Stenorrhynchus longirostris, cut off bits of Wracks, Florideæ, Ulvæ, &c, with their claws, and place them on the top of their carapaces, securing them on peculiar spiky or hooked hairs. The fragments grow firmly to the Crabs' chitinous coats, and, far from being harmful to the animals, are, on the