Page:The Outline of History Vol 1.djvu/63

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39
THE AGE OF REPTILES

There were no gay flowers, no bright autumn tints before the fall of the leaf, because there was as yet no fall of the leaf. And beyond the lower levels the world was still barren, still unclothed, still exposed without any mitigation to the wear and tear of the wind and rain.

When one speaks of conifers in the Mesozoic the reader must not think of the pines and firs that clothe the high mountain slopes of our time. He must think of low-growing evergreens. The mountains were still as bare and lifeless as ever. The only colour effects among the mountains were the colour effects of naked rock, such colours as make the landscape of Colorado so marvellous to-day.

Amidst this spreading vegetation of the lower plains the reptiles were increasing mightily in multitude and variety. They were now in many cases absolutely land animals. There are numerous anatomical points of distinction between a reptile and an amphibian; they held good between such reptiles and amphibians as prevailed in the carboniferous time of the Upper Palæozoic; but the fundamental difference between reptiles and amphibia which matters in this history is that the amphibian must go back to the water to lay its eggs, and that in the early stages of its life it must live in and under water. The reptile, on the other hand, has cut out all the tadpole stages from its life cycle, or, to be more exact, its tadpole stages are got through before the young leave the egg case. The reptile has come out of the water altogether. Some had gone back to it again, just as the hippopotamus and the otter among mammals have gone back, but that is a further extension of the story to which we cannot give much attention in this Outline.

In the Palæozoic period, as we have said, life had not spread beyond the swampy river valleys and the borders of sea lagoons and the like; but in the Mesozoic, life was growing ever more accustomed to the thinner medium of the air, was sweeping boldly up over the plains and towards the hillsides. It is well for the student of human history and the human future to note that. If a disembodied intelligence with no knowledge of the future had come to earth and studied life during the early Palæozoic age, he might very reasonably have concluded that life was