We see, then, that while the duck-billed water-mole and the echidna have found a comparatively peaceful home in Australia, where the pouched animals have reigned as monarchs, and still hold their own in spite of the animals brought in by man; and while the opossums, by taking to a tree-life, revel in the forests of America: so the imperfect-toothed animals, an old and antiquated race of Life’s children, still remain in a few scattered forms by reason of their power to adapt themselves to peculiar conditions of life. What they may have been in olden times we can scarcely guess; but one thing is certain, namely, that before such strangely different forms as the sloth, the ant-eater, the manis, and the armadillo could each have settled down and taken on their special protective armour and habits, many others must have tried, flourished awhile, and died out. When we look at the bones of the gigantic Ground-sloths or Megatheriums of olden times, which walked on four feet and are supposed to have lived by tearing the trees up by the roots and feeding on the branches, or when we examine the huge shield of the monster Glyptodon, and find that it had no movable bands between the plates such as enable the armadillo to burrow with ease, or in some kinds to roll up in a ball, we see that it is not always size and strength that win in the battle of life; but that the sloth of to-day has probably lived on because, in taking refuge in the trees, it has secured great advantages by those peculiarly long arms and twisted feet for which men used to pity it; while the ant-eaters and armadilloes in their underground homes, and the pangolins rolled up into prickly balls, show that passive resistance and retiring habits, especially if fortified by a thick skin, are sometimes quite as useful in the struggle for existence as fierce passions and aggressive weapons. [Illustration: THE PIONEERS OF THE ARMY OF MAMMALS] CHAPTER IX. FROM THE LOWER AND SMALLER MILK-GIVERS WHICH FIND SAFETY IN CONCEALMENT, TO THE INTELLIGENT APES AND MONKEYS. Having now taken leave of the curious pouch-bearers and the strange primitive sloths and armadilloes, we find ourselves left to deal with an immense multitude of modern mammalia, which have spread in endless variety over the earth, and which may be divided into five great groups--the _Insectivora_ or insect-eaters; the _Rodents_ or gnawers; the climbing and fruit-eating Lemurs and Monkeys; the _Herbivora_ or large vegetable-feeding animals; and the _Carnivora_ or flesh-eaters.