Geological Contemporaniety and Persistent Types of Life | Page 8

capricious exertions of creative power; but that they have taken place in
a definite order, the statement of which order is what men of science
term a natural law. Whether such a law is to be regarded as an
expression of the mode of operation of natural forces, or whether it is
simply a statement of the manner in which a supernatural power has

thought fit to act, is a secondary question, so long as the existence of
the law and the possibility of its discovery by the human intellect are
granted. But he must be a half-hearted philosopher who, believing in
that possibility, and having watched the gigantic strides of the
biological sciences during the last twenty years, doubts that science
will sooner or later make this further step, so as to become possessed of
the law of evolution of organic forms--of the unvarying order of that
great chain of causes and effects of which all organic forms, ancient
and modern, are the links. And then, if ever, we shall be able to begin
to discuss, with profit, the questions respecting the commencement of
life, and the nature of the successive populations of the globe, which so
many seem to think are already answered.
The preceding arguments make no particular claim to novelty; indeed
they have been floating more or less distinctly before the minds of
geologists for the last thirty years; and if, at the present time, it has
seemed desirable to give them more definite and systematic expression,
it is because paleontology is every day assuming a greater importance,
and now requires to rest on a basis the firmness of which is thoroughly
well assured. Among its fundamental conceptions, there must be no
confusion between what is certain and what is more or less probable.*
But, pending the construction of a surer foundation than paleontology
now possesses, it may be instructive, assuming for the nonce the
general correctness of the ordinary hypothesis of geological
contemporaneity, to consider whether the deductions which are
ordinarily drawn from the whole body of paleontologic facts are
justifiable.
[footnote] *"le plus grand service qu'on puisse rendre a la science est
d'y faire place nette avant d'y rien construire."--CUVIER
The evidence on which such conclusions are based is of two kinds,
negative and positive. The value of negative evidence, in connection
with this inquiry, has been so fully and clearly discussed in an address
from the chair of this Society*, which none of us have forgotten, that
nothing need at present be said about it; the more, as the considerations
which have been laid before you have certainly not tended to increase
your estimation of such evidence. It will be preferable to turn to the
positive facts of paleontology, and to inquire what they tell us.
[footnote] *Anniversary Address for 1851, 'Quart. Journ. Geol. Soc.'

vol. vii.
We are all accustomed to speak of the number and the extent of the
changes in the living population of the globe during geological time as
something enormous: and indeed they are so, if we regard only the
negative differences which separate the older rocks from the more
modern, and if we look upon specific and generic changes as great
changes, which from one point of view, they truly are. But leaving the
negative differences out of consideration, and looking only at the
positive data furnished by the fossil world from a broader point of
view--from that of the comparative anatomist who has made the study
of the greater modifications of animal form his chief business--a
surprise of another kind dawns upon the mind; and under 'this' aspect
the smallness of the total change becomes as astonishing as was its
greatness under the other.
There are two hundred known orders of plants; of these not one is
certainly known to exist exclusively in the fossil state. The whole lapse
of geological time has as yet yielded not a single new ordinal type of
vegetable structure.*
[footnote] *See Hooker's 'Introductory Essay to the Flora of Tasmania',
p. xxiii.
The positive change in passing from the recent to the ancient animal
world is greater, but still singularly small. No fossil animal is so
distinct from those now living as to require to be arranged even in a
separate class from those which contain existing forms. It is only when
we come to the orders, which may be roughly estimated at about a
hundred and thirty, that we meet with fossil animals so distinct from
those now living as to require orders for themselves; and these do not
amount, on the most liberal estimate, to more than about 10 per cent. of
the whole.
There is no certainly known extinct order of Protozoa; there is but one
among the Coelenterata--that of the rugose corals; there is none among
the Mollusca; there