The Mesozoic Era will be a
protracted reaction between two revolutions: a period of
low-lying land, great sea-invasions, and genial climate, between
two upheavals of the earth. The Tertiary Era will represent a
less sharply defined depression, with genial climate and
luxuriant life, between two such upheavals.
The Mesozaic ("middle life") Era may very fitly be described as
the Middle Ages of life on the earth. It by no means occupies a
central position in the chronicle of life from the point of view
of time or antiquity, just as the Middle Ages of Europe are by no
means the centre of the chronicle of mankind, but its types of
animals and plants are singularly transitional between the
extinct ancient and the actual modern types. Life has been lifted
to a higher level by the Permian revolution. Then, for some
millions of years, the sterner process of selection relaxes, the
warm bosom of the earth swarms again with a teeming and varied
population, and a rich material is provided for the next great
application of drastic selective agencies. To a poet it might
seem that nature indulges each succeeding and imperfect type of
living thing with a golden age before it is dismissed to make
place for the higher.
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