of palaeontology. In the first place, he
says, shells and other marine productions are found all over the surface
and in the interior of the dry land; and all calcareous rocks are made up
of their remains. Secondly, a great many of these shells which are
found in Europe are not now to be met with in the adjacent seas; and, in
the slates and other deep-seated deposits, there are remains of fishes
and of plants of which no species now exist in our latitudes, and which
are either extinct, or exist only in more northern climates. Thirdly, in
Siberia and in other northern regions of Europe and of Asia, bones and
teeth of elephants, rhinoceroses, and hippopotamuses occur in such
numbers that these animals must once have lived and multiplied in
those regions, although at the present day they are confined to southern
climates. The deposits in which these remains are found are superficial,
while those which contain shells and other marine remains lie much
deeper. Fourthly, tusks and bones of elephants and hippopotamuses are
found not only in the northern regions of the old world, but also in
those of the new world, although, at present, neither elephants nor
hippopotamuses occur in America. Fifthly, in the middle of the
continents, in regions most remote from the sea, we find an infinite
number of shells, of which the most part belong to animals of those
kinds which still exist in southern seas, but of which many others have
no living analogues; so that these species appear to be lost, destroyed
by some unknown cause. It is needless to inquire how far these
statements are strictly accurate; they are sufficiently so to justify
Buffon's conclusions that the dry land was once beneath the sea; that
the formation of the fossiliferous rocks must have occupied a vastly
greater lapse of time than that traditionally ascribed to the age of the
earth; that fossil remains indicate different climatal conditions to have
obtained in former times, and especially that the polar regions were
once warmer; that many species of animals and plants have become
extinct; and that geological change has had something to do with
geographical distribution.
But these propositions almost constitute the frame-work of
palaeontology. In order to complete it but one addition was needed, and
that was made, in the last years of the eighteenth century, by William
Smith, whose work comes so near our own times that many living men
may have been personally acquainted with him. This modest
land-surveyor, whose business took him into many parts of England,
profited by the peculiarly favourable conditions offered by the
arrangement of our secondary strata to make a careful examination and
comparison of their fossil contents at different points of the large area
over which they extend. The result of his accurate and widely-
extended observations was to establish the important truth that each
stratum contains certain fossils which are peculiar to it; and that the
order in which the strata, characterised by these fossils, are
super-imposed one upon the other is always the same. This most
important generalisation was rapidly verified and extended to all parts
of the world accessible to geologists; and now it rests upon such an
immense mass of observations as to be one of the best established
truths of natural science. To the geologist the discovery was of infinite
importance as it enabled him to identify rocks of the same relative age,
however their continuity might be interrupted or their composition
altered. But to the biologist it had a still deeper meaning, for it
demonstrated that, throughout the prodigious duration of time
registered by the fossiliferous rocks, the living population of the earth
had undergone continual changes, not merely by the extinction of a
certain number of the species which had at first existed, but by the
continual generation of new species, and the no less constant extinction
of old ones.
Thus the broad outlines of palaeontology, in so far as it is the common
property of both the geologist and the biologist, were marked out at the
close of the last century. In tracing its subsequent progress I must
confine myself to the province of biology, and, indeed, to the influence
of palaeontology upon zoological morphology. And I accept this
limitation the more willingly as the no less important topic of the
bearing of geology and of palaeontology upon distribution has been
luminously treated in the address of the President of the Geographical
Section.<3>
The succession of the species of animals and plants in time being
established, the first question which the zoologist or the botanist had to
ask himself was, What is the relation of these successive species one to
another? And it is a curious circumstance that the most important event
in the history of palaeontology
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