ion, it is an unsafe thing
to infer the non-occurrence of an event from a mere silence of the
historian--and this especially in matters of comparatively small detail,
such as would correspond (in the present analogy) to the occurrence of
_species_ and _genera_ as connecting links. And, of course, if the
history had only come down to us in fragments, no one would attach any
importance at all to what might have been only the _apparent_ silence of
the historian.

In view, then, of the unfortunate imperfection of the geological record
_per se_, as well as of the no less unfortunate limitation of our means
of reading even so much of the record as has come down to us, I conclude
that this record can only be fairly used in two ways. It may fairly be
examined for positive testimony against the theory of descent, or for
proof of the presence of organic remains of a high order of development
in a low level of strata. And it may be fairly examined for negative
testimony, or for the absence of connecting links, if the search be
confined to the larger taxonomic divisions of the fauna and flora of the
world. The more minute these divisions, the more restricted must have
been the areas of their origin, and hence the less likelihood of their
having been preserved in the fossil state, or of our finding them even
if they have been. Therefore, if the theory of evolution is true, we
ought not to expect from the geological record a full history of
_specific_ changes in any but at most a comparatively small number of
instances, where local circumstances happen to have been favourable for
the writing and preservation of such a history. But we might reasonably
expect to find a general concurrence of geological testimony to the
larger fact--namely, of there having been throughout all geological time
a uniform progression as regards the larger taxonomic divisions. And, as
I will next proceed to show, this is, in a general way, what we do find,
although not altogether without some important exceptions, with which I
shall deal in an Appendix.

There is no _positive_ proof _against_ the theory of descent to be drawn
from a study of palaeontology, or proof of the presence of any kind of
fossils in strata where the fact of their presence is incompatible with
the theory of evolution. On the other hand, there is an enormous body of
uniform evidence to prove two general facts of the highest importance in
the present connexion. The first of these genera