es on the little island in the Crystal Palace
grounds. Every dog has his day, and the reptiles had _their_ day in the
secondary period. The forms into which they developed were certainly
every whit as large as any ever seen on the surface of this planet, but
not, as I have already shown, appreciably larger than those of the
biggest cetaceans known to science in our own time.

During the very period, however, when enaliosaurians and pterodactyls
were playing such pranks before high heaven as might have made
contemporary angels weep, if they took any notice of saurian morality, a
small race of unobserved little prowlers was growing up in the dense
shades of the neighbouring forests which was destined at last to oust
the huge reptiles from their empire over earth, and to become in the
fulness of time the exclusively dominant type of the whole planet. In
the trias we get the first remains of mammalian life in the shape of
tiny rat-like animals, marsupial in type, and closely related to the
banded ant-eaters of New South Wales at the present day. Throughout the
long lapse of the secondary ages, across the lias, the oolite, the
wealden, and the chalk, we find the mammalian race slowly developing
into opossums and kangaroos, such as still inhabit the isolated and
antiquated continent of Australia. Gathering strength all the time for
the coming contest, increasing constantly in size of brain and keenness
of intelligence, the true mammals were able at last, towards the close
of the secondary ages, to enter the lists boldly against the gigantic
saurians. With the dawn of the tertiary period, the reign of the
reptiles begins to wane, and the reign of the mammals to set in at last
in real earnest. In place of the ichthyosaurs we get the huge cetaceans;
in place of the deinosaurs we get the mammoth and the mastodon; in place
of the dominant reptile groups we get the first precursors of man
himself.

The history of the great birds has been somewhat more singular. Unlike
the other main vertebrate classes, the birds (as if on purpose to
contradict the proverb) seem never yet to have had their day.
Unfortunately for them, or at least for their chance of producing
colossal species, their evolution went on side by side, apparently, with
that of the still more intelligent and more powerful mammals; so that,
wherever the mammalian type had once firmly established itself, the
birds were compelled to limit their aspirations to a very modest