tion of the record in one
region cannot be made good by thus interpolating the fossils of another
region. And we must remember it is by selecting the cases where this
cannot be done that the objection before us is made to appear
formidable. In other words, _unless_ whole groups of new species which
are unknown in formation A appear suddenly in formation C of one region
(X), where the intermediate formation B is absent; and _unless_ in some
other region (Y), where B is present, the fossiliferous contents of B
fail to supply the fossil ancestry of the new species in A (X); _unless_
such a state of matters is found to obtain, the objection before us has
nothing to say. But at best this is negative evidence; and, in order to
consider it fairly, we ought to set against it the cases where an
interposition of fossils found in B (Y) _does_ furnish the fossil
ancestry of what would _otherwise_ have been an abrupt appearance of
whole groups of new species in A (X). Now such cases are neither few
nor unimportant, and therefore they deprive the objection of the force
it would have had if the selected cases to the contrary were the general
rule.

In addition to these considerations, the following, some of which are of
a more special kind, appear to me so important that I will quote them
almost _in extenso_.

We continually forget how large the world is, compared with the
area over which our geological formations have been carefully
examined: we forget that groups of species may elsewhere have long
existed, and have slowly multiplied, before they invaded the
ancient archipelagoes of Europe and the United States. We do not
make due allowance for the intervals of time which have elapsed
between our consecutive formations,--longer perhaps in many cases
than the time required for the accumulation of each formation.
These intervals will have given time for the multiplication of
species from some one parent form; and, in the succeeding
formation, such groups of species will appear as if suddenly
created.

I may here recall a remark formerly made, namely, that it might
require a long succession of ages, to adapt an organism to some new
and peculiar line of life, for instance, to fly through the air;
and consequently that the transitional form would often long remain
confined to some one region; but that, when this adaptation had
once been effected,