Even more remarkable are the "masking" habits of the Spider Crabs (Oxyrhyncha). In these the carapace is almost always covered with sea-weeds, zoophytes, and other organisms which afford a very effective disguise. For example, specimens of the British species of _Hyas_ (_H. araneus_ and _H. coarctatus_) and _Maia_ (_M. squinado_--Plate XIII.), which are very common on our coasts, readily escape the notice of the collector, as they lurk in the rock-pools. They are slow-moving animals, and the carapace and limbs are usually quite hidden by dense tufts of growing sea-weed, sponges, and other organisms. By observing the Crabs in an aquarium, it has been found that they actually dress themselves, plucking pieces of weed and the like and placing them on the carapace, where they are held in position by numerous hooked hairs. The transplanted fragments continue to live and grow until the Crab appears like a miniature moving forest. Still more strange is the fact that the Crabs appear to be able in some degree to adapt the nature of their covering to their surroundings. It has been found that specimens dressed in sea-weeds, when placed in an aquarium among sponges, picked off the weeds from their bodies and limbs, and planted fragments of sponge in their place. Not only does this habit afford the Crabs protective concealment, but it may also in some cases serve as a source of food-supply. The late Dr. David Robertson, of Cumbrae, one of the most observant of marine naturalists, saw the Crab _Stenorhynchus_ (or _Macropodia_) _longirostris_ picking food-particles from among the vegetation on its body, and conveying them to its mouth. Many Crustacea of different orders seek concealment and protection by burying themselves in sand. A pool left by the tide on a sandy beach may at first sight appear empty of all life, but if it be watched for a little while a greyish, shadowy form may often be seen to dart across it, to settle on the bottom with a little puff of sand, and to disappear. Even a close scrutiny of the spot will hardly discover anything, but with a hand-net one may succeed in scooping up, before it can dart away again, a specimen of the Common Shrimp (_Crangon vulgaris_--see Fig. 78, p. 244), whose translucent body is finely mottled with greyish-brown so as to match exactly the sand among which it rests.