togaeal province. But, at the end of the Triassic
period, the movement of depression recommenced in our area, though
it was doubtless balanced by elevation elsewhere; modification and
development, checked in the one province, went on in that "elsewhere;"
and the chief forms of Mammals, Birds, and Reptiles, as we know them,
were evolved and peopled the Mesozoic continent. I conceive Australia
to have become separated from the continent as early as the end of
the Triassic epoch, or not much later. The Mesozoic continent must, I
conceive, have lain to the east, about the shores of the North Pacific
and Indian Oceans; and I am inclined to believe that it continued
along the eastern side of the Pacific area to what is now the province
of Austro-Columbia, the characteristic fauna of which is probably a
remnant of the population of the latter part of this period.

Towards the latter part of the Mesozoic period the movement of
upheaval around the shores of the Atlantic once more recommenced,
and was very probably accompanied by a depression around those of the
Pacific. The Vertebrate fauna elaborated in the Mesozoic continent
moved westward and took possession of the new lands, which gradually
increased in extent up to, and in some directions after, the Miocene
epoch.

It is in favour of this hypothesis, I think, that it is consistent
with the persistence of a general uniformity in the positions of the
great masses of land and water. From the Devonian period, or earlier,
to the present day, the four great oceans, Atlantic, Pacific, Arctic,
and Antarctic, may have occupied their present positions, and only
their coasts and channels of communication have undergone an incessant
alteration. And, finally, the hypothesis I have put before you
requires no supposition that the rate of change in organic life has
been either greater or less in ancient times than it is now; nor
any assumption, either physical or biological, which has not its
justification in analogous phenomena of existing nature.

I have now only to discharge the last duty of my office, which is
to thank you, not only for the patient attention with which you have
listened to me so long to-day, but also for the uniform kindness with
which, for the past two years, you have rendered my endeavours
to perform the important, and often laborious, functions of your
President a pleasure instead of a burden.

X.

MR. DARWIN'S CRITICS.[1]

The gradual lapse of time