If we now glance back in imagination over the almost endless variety of creatures which we have met with since we started with the fish, we must acknowledge that even if there were no other kinds than those we have already mentioned, the world would be very full of different living beings, and that to succeed in the struggle for life in the midst of such a multitude, new forms must be endowed with great strength or armed with specially effective weapons. Such animals, however, we know were already in the field, for we saw at the beginning of the last chapter that, together with the small rodents, insect-eaters, and lemurs, there were two groups of much larger animals, first the _Herbivora_ or grass-feeders, including the hoofed animals (_Ungulata_) and the elephants; and secondly, their great enemies the _Carnivora_ or flesh-feeders. Now these two groups, on account of their size, strength, and agility, have spread very widely over the earth, especially the grass-feeders, for there is no part of the world which has not some vegetable-feeding animal in it, if only a few green shoots grow there. It is true the Rodents take some part of this green food, but then they are small and insignificant compared to the large Rhinoceroses, Elephants, Hippopotamuses, Oxen, Antelopes, Goats, Pigs and Sheep, which roam over wide spaces, and are even less restricted than the flesh-eating animals, for they live in the open air or the thick jungle, never in caves and holes, and their young ones are born wherever they may happen to be, and in a few hours run by their mother’s side, so that young and old wander together wherever food and shelter is to be found. And so we shall see that these vegetable-feeders have filled every spot where they could possibly find a footing. In the regions of snow and ice the reindeer in Europe, and the elk and musk-sheep in America, rake the snow to uncover their scanty food, while the burning deserts of North Africa and East Asia have bred their camels and wild asses, and those of South Africa their quaggas. On the prairies of America the bison, and on the plains of Asia the wild cattle, feed in herds of thousands, while the zebra courses over the African hills. If we look to the tops of mountains, to dangerous crags where the merest tufts of grass are to be found, there we meet with the goats and sheep in India and Asia, the chamois and ibex in Europe, the big-horn sheep in the Rocky Mountains of America; or if we turn to the dense forests and tropical jungles, there we find the giraffes in Africa, the elephants, rhinoceroses, buffaloes, antelopes, and wild boars in Africa and India, some feeding on the branches of the trees, some grazing on the grasses and lower brushwood, and some digging up roots and underground food. Only the rivers remain, and here too, in Africa, the hippopotamus has taken possession, feeding on the water plants and wallowing on the muddy banks.