The Rise and Progress of Palaeontology | Page 8

which immediately succeeded William
Smith's generalisation was a discovery which, could it have been
rightly appreciated at the time, would have gone far towards suggesting
the answer, which was in fact delayed for more than half a century. I
refer to Cuvier's investigation of the mammalian fossils yielded by the
quarries in the older tertiary rocks of Montmartre, among the chief
results of which was the bringing to light of two genera of extinct
hoofed quadrupeds, the Anoplotherium and the
Palaeotherium. The rich materials at Cuvier's disposition
enabled him to obtain a full knowledge of the osteology and of the
dentition of these two forms, and consequently to compare their
structure critically with that of existing hoofed animals. The effect of
this comparison was to prove that the Anoplotherium, though it
presented many points of resemblance with the pigs on the one hand
and with the ruminants on the other, differed from both to such an
extent that it could find a place in neither group. In fact, it held, in some
respects, an intermediate position, tending to bridge over the interval
between these two groups, which in the existing fauna are so distinct.
In the same way, the Palaeotherium tended to connect forms so
different as the tapir, the rhinoceros, and the horse. Subsequent
investigations have brought to light a variety of facts of the same order,
the most curious and striking of which are those which prove the
existence, in the mesozoic epoch, of a series of forms intermediate
between birds and reptiles--two classes of vertebrate animals which at
present appear to be more widely separated than any others. Yet the
interval between them is completely filled, in the mesozoic fauna, by

birds which have reptilian characters, on the one side, and reptiles
which have ornithic characters, on the other. So again, while the group
of fishes, termed ganoids, is, at the present time, so distinct from that of
the dipnoi, or mudfishes, that they have been reckoned as distinct
orders, the Devonian strata present us with forms of which it is
impossible to say with certainty whether they are dipnoi or whether
they are ganoids.
Agassiz's long and elaborate researches upon fossil fishes, published
between 1833 and 1842, led him to suggest the existence of another
kind of relation between ancient and modern forms of life. He observed
that the oldest fishes present many characters which recall the
embryonic conditions of existing fishes; and that, not only among
fishes, but in several groups of the invertebrata which have a long
palaeontological history, the latest forms are more modified, more
specialised, than the earlier. The fact that the dentition of the older
tertiary ungulate and carnivorous mammals is always complete, noticed
by Professor Owen, illustrated the same generalisation.
Another no less suggestive observation was made by Mr. Darwin,
whose personal investigations during the voyage of the Beagle
led him to remark upon the singular fact, that the fauna, which
immediately precedes that at present existing in any geographical
province of distribution, presents the same peculiarities as its successor.
Thus, in South America and in Australia, the later tertiary or quaternary
fossils show that the fauna which immediately preceded that of the
present day was, in the one case, as much characterised by edentates
and, in the other, by marsupials as it is now, although the species of the
older are largely different from those of the newer fauna.
However clearly these indications might point in one direction, the
question of the exact relation of the successive forms of animal and
vegetable life could be satisfactorily settled only in one way; namely,
by comparing, stage by stage, the series of forms presented by one and
the same type throughout a long space of time. Within the last few
years this has been done fully in the case of the horse, less completely
in the case of the other principal types of the ungulata and of the

carnivora; and all these investigations tend to one general result,
namely, that, in any given series, the successive members of that series
present a gradually increasing specialisation of structure. That is to say,
if any such mammal at present existing has specially modified and
reduced limbs or dentition and complicated brain, its predecessors in
time show less and less modification and reduction in limbs and teeth
and a less highly developed brain. The labours of Gaudry, Marsh, and
Cope furnish abundant illustrations of this law from the marvellous
fossil wealth of Pikermi and the vast uninterrupted series of tertiary
rocks in the territories of North America.
I will now sum up the results of this sketch of the rise and progress of
palaeontology. The whole fabric of palaeontology is based upon two
propositions: the first is, that fossils are the remains of animals and
plants;