The commonest kind of crab in Orkney is the green shore-crab. He is on the whole a bold animal, but when frightened he runs away with great speed. He moves sideways, and thus meets with less resistance from the water than if he were to move directly forward. Usually, however, he does not walk fast, but creeps over the bottom in a leisurely fashion. When seizing his food he comes up to it “head on,” his nipping claws held wide apart; when he is near enough, he suddenly brings them together, and begins to tear up the food in little bits and pack it into his mouth. His eyes are placed on the tip of movable projections, so that they command a wide view. He cannot see behind him, however, or under his body, and he usually keeps his eyes fixed in the direction in which he is going. When he is resting, his eyes are ever on the watch. Every little movement on the beach near him he notices at once. The crab has a peculiar method of feeding. His mouth is just under his head, and the opening is guarded by two flat jointed plates, one on each side of his mouth. If you pull these two plates apart—after having arranged with a friend to hold his pincers—you can see where his mouth is, and you may notice two strong things which look like teeth. These are really his jaws; they move from side to side, and not up and down like our jaws. To see how he feeds, you must put him into a glass jar, and look up from below while he is eating a bit of fish. He tears it up with his pincers, and puts little bits into his mouth, the parts of which move from side to side as he eats. He is not very particular as to what he eats. He is, indeed, a cannibal, and will eat the crushed leg of another crab as readily as anything else. He is one of the most useful animals on the beach, however, and has been called the scavenger of the shore. In fact, if one wishes to get the flesh cleaned off the skeleton of any large animal, there is no easier method than to lay it on the beach, well below high-water mark, and build stones around it, leaving spaces between them to admit crabs. As we have already said, the crab is bold and fearless. He is safe in his coat of armour, and his pincers are powerful weapons of offence and defence. When fighting he rears himself up and throws his nipping legs far apart with the pincers wide open. He then looks a formidable animal; and he really is formidable, for with these legs he can protect almost any part of his body, and the strength of his grip is considerable. Take up a dead crab and examine his biting leg. The different parts are joined by hinges. Each hinge allows of motion only in one plane, but the various planes are so adjusted that the limb can be moved in almost any direction. Only one part of his body cannot be touched by his pincers, and that is his back. If you wish to grasp a live crab with impunity, seize him across the back just where his walking legs join the body. He may struggle as he pleases, but he cannot nip you.