So we see that while the vegetable-feeding animals have three characters in common, namely, large flat grinders, a capacious stomach, and defensive weapons, their defences, on the other hand, may be of three different kinds, and they may depend upon horns, hoofs, or teeth for protection. Now in the beginning, when we first meet with the milk-givers, these defences were not so complete in any of the vegetable-feeders as they are now. Of the elephants alone it may perhaps be said that they had large and formidable ancestors.[159] As to the rest, the huge hippopotamus and sharp-tusked boar were only represented by small animals;[160] and even later, when the hogs branched off in a line of their own, they had at first only ordinary teeth, which did not grow out as tusks. So, too, the fierce horned rhinoceros had as an ancestor a hornless tapir-like creature,[161] and the graceful hoofed horse a little creature no larger than a fox, with five separate toes on his feet.[162] Lastly, all the horned animals which chew the cud,--oxen, buffaloes, antelopes, and deer,--were nowhere to be seen, and in their place were only some small elegant creatures without horns.[163] It is only at a later period when the flesh-feeding animals grew strong and dangerous, and the vegetable-feeders had to struggle for their lives, that we begin to find the remains of hogs and hippopotamuses with tusks, rhinoceroses with nose-bones, and fleet horses which could take to their heels, or bite and kick their enemy to death; of stags with antlers, ever increasing in size; and of bulls and buffaloes, goats and antelopes, with true horns. For not only by this time were they persecuted by the flesh-feeders, but they themselves were becoming very numerous, and it was the strongest only that could secure feeding-grounds or carry off wives. * * * * *