This is the egg of the Dog-fish, which is really a kind of small shark. It is not big or strong enough to be dangerous to human beings; but it is a terrible enemy to such small fishes as pilchards and herrings. For a number of these creatures form themselves into a band and go hunting together, just like a pack of wild dogs. And they will follow the shoal about day after day, snapping up the poor helpless fishes in hundreds and thousands. When a dog-fish lays its eggs, it seems to fasten them down by their tendrils to the weeds which are growing at the bottom of the sea; and these hold them so firmly that unless the weeds are torn up with them, they never break away. At each end of the egg is a small hole, allowing a current of water to pass over the little fish inside it. And at one end there is a slit, just like that in the egg of the skate, which can only be pushed open from the inside. So the little dog-fish can get out, while its enemies cannot get in. [Illustration: PLATE VI 1. THE EGG OF SKATE. 2. THE EGG OF DOG-FISH.] Very often, after a violent storm, you may find a dead dog-fish lying upon the shore; and even if you have never seen one of these creatures before you can tell at once what it is, because its skin is so rough that it feels exactly like a piece of sand-paper. So this skin is often used for covering the handles of swords, in order to give a firm grip; and sometimes narrow strips of it are fastened to the sides of boxes of lucifer matches. CHAPTER II THE MOLLUSCS PLATE VII THE CUTTLE (1 and 2) We now come to the Molluscs, or Soft-bodied Animals, of which there are a very great many. Some of them live in shells, like the oyster and the whelk, and are often spoken of as “shell-fishes.” But they are not really fishes at all, for they have no bones as fishes have, and are made in quite a different way. And there are just a few of them which have no shells at all. One of these is that very curious creature which we call the Cuttle. You may sometimes find it in the rock-pools, lurking in the crevices among the rocks, or hiding under the masses of sea-weeds which grow round the edges. It has a soft, white, bag-like body, and a big head, on which are two great staring black eyes. Just above these eyes eight long slender arms spring out; for cuttles keep their arms on their heads instead of on their bodies! And another arm which is even longer still, and is flattened out at the end into a kind of oval plate, hangs down on either side. All these arms are set with rows of round suckers, which are so strong that if even a small cuttle catches hold of you, it will not be very easy to make him let go. So if you do happen to find a cuttle in a rock-pool it will be better to watch him in the water, without attempting to catch him.