CHAPTER XII. THE AGE OF REPTILES
From one point of view the advance of life on the earth seems to
proceed not with the even flow of a river, but in the successive
waves of an oncoming tide. It is true that we have detected a
continuous advance behind all these rising and receding waves,
yet their occurrence is a fact of some interest, and not a little
speculation has been expended on it. When the great procession of
life first emerges out of the darkness of Archaean times, it
deploys into a spreading world of strange Crustaceans, and we
have the Age of Trilobites. Later there is the Age of Fishes,
then of Cryptogams and Amphibia, and then of Cycads and Reptiles,
and there will afterwards be an Age of Birds and Mammals, and
finally an Age of Man. But there is no ground for mystic
speculation on this circumstance of a group of organisms fording
the earth for a few million years, and then perishing or
dwindling into insignificance. We shall see that a very plain and
substantial process put an end to the Age of the Cycads,
Ammonites, and Reptiles, and we have seen how the earlier
dynasties ended.
The phrase, however, the Age of Reptiles, is a fitting and true
description of the greater part of the Mesozoic Era, which lies,
like a fertile valley, between the Permian and the Chalk
upheavals.
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