eason
to believe that much of the coal was formed by the accumulation of spores
and sporangia on dry land. But if we consider the matter more closely, I
think that this apparent objection loses its force. It is clear that,
during the Carboniferous epoch, the vast area of land which is now
covered by Coal-measures must have been undergoing a gradual depression.
The dry land thus depressed must, therefore, have existed, as such,
before the Carboniferous epoch--in other words, in Devonian times--and
its terrestrial population may never have been other than such as existed
during the Devonian, or some previous epoch, although much higher forms
may have been developed elsewhere.

Again, let me say that I am making no gratuitous assumption of
inconceivable changes. It is clear that the enormous area of Polynesia
is, on the whole, an area over which depression has taken place to an
immense extent; consequently a great continent, or assemblage of
subcontinental masses of land must have existed at some former time, and
that at a recent period, geologically speaking, in the area of the
Pacific. But if that continent had contained Mammals, some of them must
have remained to tell the tale; and as it is well known that these
islands have no indigenous _Mammalia_, it is safe to assume that none
existed. Thus, midway between Australia and South America, each of which
possesses an abundant and diversified mammalian fauna, a mass of land,
which may have been as large as both put together, must have existed
without a mammalian inhabitant. Suppose that the shores of this great
land were fringed, as those of tropical Australia are now, with belts of
mangroves, which would extend landwards on the one side, and be buried
beneath littoral deposits on the other side, as depression went on; and
great beds of mangrove lignite might accumulate over the sinking land.
Let upheaval of the whole now take place, in such a manner as to bring
the emerging land into continuity with the South-American or Australian
continent, and, in course of time, it would be peopled by an extension of
the fauna of one of these two regions--just as I imagine the European
Permian dry land to have been peopled.

I see nothing whatever against the supposition that distributional
provinces of terrestrial life existed in the Devonian epoch, inasmuch as
M. Barrande has proved that they existed much earlier. I am aware of no
reason for doubting that, as regards the grades of