Down in the middle of all these branching arms, just where they spring from the head, are two very curious organs. The first of these is the beak, which is very strong, very sharp, and a good deal hooked. In fact, it is rather like that of a parrot. The other consists of two tubes which run downwards into the head, lying side by side together like the barrels of a double-barrelled gun. These tubes are called the “siphon,” and they are used for three purposes. First of all, they are used for breathing. The cuttle breathes water by means of gills, like those of fishes, which lie inside the head; and the water passes down to them through one of the siphon tubes, and then goes out again through the other. Next, they are used for swimming. When a cuttle wants to swim it gathers all its arms together in front of its head, fills both its siphon tubes with water, and then squirts their contents out again as hard as it can. The result is that two jets of water come rushing out of its head with such force that the surrounding water cannot give way fast enough before them. So they push the cuttle backwards so swiftly that if it were to dart across the pool you would hardly be able to follow its movements. The third use of the siphon tubes is a very strange one indeed. Sometimes while you are looking at a cuttle in a rock-pool, the water all round it will suddenly become quite dark, just as if a quantity of ink had been poured into the pool. And so it has; for inside its body the cuttle has a bag which contains a quantity of a deep black liquid called “sepia.” This bag is surrounded by powerful muscles, and opens into the siphon tubes; so that when the animal contracts the muscles, the sepia is squirted out into the pool. It always does this if it is frightened; and under cover of the darkened water it nearly always succeeds in making its escape. Inside its body the cuttle also has a very curious object which is generally called a “cuttle-bone.” It is not really a bone, however, but is made of almost pure chalk, and seems to act as a kind of support for the bodily organs. [Illustration: PLATE VII 1. THE CUTTLE. 2. THE EGGS OF CUTTLE.] Another very odd thing about the cuttle is the way in which it lays its eggs. These look just like purple grapes, and each has a small stalk, by means of which they are fastened together in bunches. Indeed, the fishermen always call them “sea-grapes.” You may often find them lying about upon the beach in early spring, and if you open one of them carefully, you will find a little baby cuttle inside it. PLATE VIII THE WHELK (1 and 2) Everybody knows the shells of whelks by sight, and you can hardly take a walk along the sea-shore without seeing hundreds of them lying about on the beach. And great numbers of whelks are caught for human food, and also to serve as bait for fishes.