The Blue Whales which come to this country are between seventy and eighty feet long (there is really no room to give you a picture of one) and weigh between a hundred and fifty and two hundred tons. The Pygmy Shrewmouse, tail and all, is less than three inches long and weighs about a tenth of an ounce. Now I know that measurements are difficult things for young folks to understand, so I will try to make you see the difference between these two animals of ours in a different way. I expect we all know what a lawn-tennis court looks like. Two Blue Whales would just fill a lawn-tennis court, but if we wanted to fill a lawn-tennis court with Pygmy Shrewmice, we should want five-hundred thousand of them, and if we could lift a Blue Whale on an enormous pair of scales, and tried to balance him with Pygmy Shrewmice, we should want--how many do you think? We should want more than _seventy millions_ of them. [Illustration: THE COMMON SHREWMOUSE, WHO IS HALF AS BIG AGAIN AS THE PYGMY] It is wonderful to think that the wee Pygmy and the huge Whale should belong to the same Class of creatures. But it is so. Nearly all the bones in the Pygmy (some are scarcely thicker than a hair) can be matched by the same sort of bones in the Blue Whale. If the Blue Whale were a fish (and he certainly looks like one) his bones would be quite different and quite differently arranged, and from this we know that the Whale is not a fish like a Shark, but an animal like a Seal, or a Pygmy Shrewmouse or one of ourselves. Now we must look at the pictures. You will see at once what a long nose the Pygmy has got. This nose is very useful to him, for much of his food is tiny insects, and he pokes his nose into tiny holes after them. You can't see his teeth in the pictures, which is a pity, for they are very curious teeth, and the front ones, instead of pointing up and down like ours do, point outwards rather, and come together like a pair of tweezers. This helps him to catch insects too, and to pull little snails out of their shells. I don't think his teeth are strong enough to crack snail shells, but his dark-brown cousin, the Common Shrewmouse (his picture is on page 181), cracks snail shells quite easily, and so does his black cousin, the Water Shrewmouse. [Illustration: THE WATER SHREWMOUSE, WHO IS NEARLY HALF AS BIG AGAIN AS THE COMMON SHREWMOUSE] What does the great Blue Whale eat, you ask? I expect you will be surprised to hear that he eats much the same kind of things as the Pygmy--small slug-like creatures, scarcely an inch long, which swarm in parts of the sea. Of course he eats barrelfuls at once.