It is very pleasant to read the accounts given by other people of what they have observed, but even better still to learn to use our own eyes. Try this plan, and you will be surprised at the many curious and beautiful things about the ways of animals which you can find out for yourself. You remember, when we were talking about fishes and birds, we found that they both belong to the great group of animals called Vertebrate, from having a backbone made of many pieces beautifully fitted together. We are now going to speak of the last class in that great group--the Mammalia, so called because they feed their young, not as birds do, with insects or grain, but with milk. They are chiefly "four-footed beasts of the earth," and are covered with hair or fur. In this class extremes meet; we find the great elephant and the playful little squirrel, the kingly lion and the timid mouse which is said to have set him free when snared in the hunter's net. To this class also belong the land-monsters of bygone days, whose skeletons you may see in museums: such as the Mammoth, or hairy elephant, found in the British Isles, and also over half the globe; the Mastodon, another elephantine extinct monster, whose remains are found in America; the Woolly Rhinoceros, with two large horns on his face, dug out of the frozen soil of Siberia; the Great Irish Deer, whose antlers measured 9 feet from tip to tip; and Giant Sloths of South America, inhabitating the same region as the Sloths of to-day. But we must leave the "unnumbered, unremembered tribes" of buried creatures which once trod this earth; and speaking only of those now alive, I must tell you that in the first Division of the great class, Mammalia, naturalists place the Quadrumana, or four-handed creatures. This name is given to all monkeys; because their great-toes are like thumbs, so that they can take hold of the branches in the forests where they spend their lives, quite as well with their feet as with their hands.