ern hemisphere and
the southern, and along every ridge of land that connected them, these
sluggish but formidable monsters filled the stage. Every conceivable
device in the way of arms and armour, brute strength and means of
escape, seemed to be adopted in their development, as if they were the
final and indestructible outcome of the life-principle. And within a
single geological period the overwhelming majority of them, especially
the larger and more formidable of them, were ruthlessly slain, leaving
not a single descendant on the earth. Let us see what types of animals
were thus preferred to them in the next great application of selective
processes.

CHAPTER XIII. THE BIRD AND THE MAMMAL

In one of his finest stories, Sur La Pierre Blanche, Anatole France
has imagined a group of Roman patricians discussing the future of their
Empire. The Christians, who are about to rise to power on their ruin,
they dismiss with amiable indifference as one of the little passing
eccentricities of the religious life of their time. They have not the
dimmest prevision, even as the dream of a possibility, that in a century
or two the Empire of Rome will lie in the dust, and the cross will tower
above all its cities from York to Jerusalem. If we might for a moment
endow the animals of the Mesozoic world with AEsopian wisdom, we could
imagine some such discussion taking place between a group of Deinosaur
patricians. They would reflect with pride on the unshakable empire of
the reptiles, and perhaps glance with disdain at two types of animals
which hid in the recesses or fled to the hills of the Jurassic world.
And before another era of the earth's story opened, the reptile
race would be dethroned, and these hunted and despised and feeble
eccentricities of Mesozoic life would become the masters of the globe.

These two types of organisms were the bird and the mammal. Both existed
in the Jurassic, and the mammals at least had many representatives
in the Triassic. In other words, they existed, with all their higher
organisation, during several million years without attaining power. The
mammals remained, during at least 3,000,000 years, a small and obscure
caste, immensely overshadowed by the small-brained reptiles. The birds,
while making more progress, apparently, than the mammals, were far
outnumbered by the flying reptiles until the last part of the Mesozoic.
Then there was another momentous turn of the wheel of fate, and they
emerged