Page:Popular Science Monthly Volume 22.djvu/769

Rh, and the armadillo, whose back is covered with long shields like the crocodile.

Having now taken leave of the curious pouch-bearers and the strange primitive sloths and armadillos, 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.

It is clear that the Rodents and Insectivores do not hold their place in the world by strength or audacity. Both lowly groups, of simple structure and with comparatively feeble brains, they have chiefly escaped destruction from higher forms by means of their nocturnal and burrowing habits or arboreal lives, and the marvelous rapidity with which they breed, combined with their power of sleeping without food during; the winter in all cold countries. But the insect-eaters have no water-animal to match the beaver among rodents in sagacity or engineering. With his chisel-like front teeth he gnaws a deep notch in the trunk of a larch or pine or willow, and then, going round to the other side, begins work there till the trunk is severed and falls heavily on the side of the deep notch, and therefore away from himself. He always makes the deep notch in the trunk on the side near the water, so that the tree in falling comes as near as possible to the stream. Then, after stripping off the bark and gnawing the trunk into pieces about six feet long, he uses his fore-paws and his teeth to drag them into position to build his dam. He does not always clear away all the branches, but he and his companions place the logs with these lying down the stream, so that they act as supports to resist the current and prevent the dam being washed away. Thus they make a broad foundation, sometimes as much as six feet wide, and upon this they pile logs and stones and mud till they have made a barrier often ten feet high and more than a hundred feet long. The lighter branches he uses to make his oven-shaped lodge, laying them down in basket-work shape, plastering them with mud, grass, and moss, and lining the chambers with wood-fiber and dry grass.

There remain to be noticed two groups of much larger animals: first, the Herbivora, or grass-feeders; and, secondly, their great enemies, the Carnivora, or flesh-feeders. We shall see that the vegetable-feeders have filled every spot where they could possibly find a footing, and if we could only trace out their pedigree we should be surprised to find how wonderfully each one has become fitted for the special work it has to do. But three things they all require and have. The first of these is a long face and freely-moving under jaw, with large grinding teeth to work up and chew the vegetable food; the second, a capacious stomach to hold and digest green meat enough to