WHEN THE WORLD WAS YOUNG 195
in the new red sandstone, could have looked but little different from our friends of to-day.1
It is an established fact that large animals more quickly become extinct than small ones. Their families are fewer, to begin with, and they need more food and water ; it is also more difficult for them to hide, and to escape from their enemies. For these reasons, among others, vast hordes of huge monsters have died out, and given place to smaller ones, both in land and sea. And no doubt, if the world goes on long enough, other changes will take place ; the old order of things will be swept away, and men will some day be puzzling over the skeletons of cats and the bones of canary birds.
1 From Owen's Palaeontology; Manual of Palaeontology, by Nicholson and Lyddeker, and Hutchinson's Extinct Monsters.