On its head, as perhaps you know, a crab has two pairs of feelers. We call them the “lesser feelers” and the “greater feelers.” Now if you were to look at the first joint of the lesser feelers through a good microscope, you would find on each a little gland, or bag, containing a very tiny drop of salt and water. These are the crab’s ears. Of course they are not nearly so good as our ears are. Indeed, I do not think that a crab can hear sounds in the air at all. But water carries sounds much more readily than air does, so that if you were to dive into a lake, or into the sea, on a calm, still day you could easily hear the beat of the oars in a boat half a mile away. And the ears of the crab are made in such a way that they can hear sounds in the water quite well, even though they may be deaf to sounds in the air. Then if you look at the first joint of the greater feelers through the microscope, you will see two other tiny glands. These are the crab’s noses, by which it can smell odours in the water just as we can smell odours in the air. It always seems to find its food by scent, and if one of those basket-like traps which we call crab-pots is baited with a few pieces of decaying fish and lowered into the sea, crabs will smell the bait from quite a long distance away, and come hurrying up to obtain a share in the banquet. And they seem to do so by means of those odd little noses on the lower joints of their greater feelers. PLATE XXI THE EDIBLE CRAB Now let me tell you something about the different kinds of crabs which you may find on the shore. First of all, of course, there is the Edible Crab. This is the crab which is so largely used for food, and which you may see in any fishmonger’s shop. Sometimes it grows to a very great size, and has claws so big and strong that if it were to seize a man by the wrist he would find it very difficult indeed to set himself free. You will not find crabs as big as this among the rocks, for these giant creatures always live in rather deep water. But one often discovers a crab four or five inches across hiding in a rock-pool, and even he is quite big and strong enough to give one a very sharp nip. [Illustration: PLATE XXI THE EDIBLE CRAB.] It is rather amusing to get one of these crabs out on to the open sand, and then to stand just in front of him. He will at once raise both his great claws and hold them in readiness to strike at you if you attempt to seize him. Then if you walk slowly round and round him he will turn round and round too, so as to keep facing you, over and over and over again. And if you put your hand anywhere near him he will snap at it so quickly that it is really not at all easy to avoid his stroke. Edible crabs often have their shells covered with barnacles and the tubes of some of the sea-worms. Old crabs, indeed, which no longer change their coats of mail every year, are often so covered with these creatures that one can hardly see their shells at all. PLATE XXII