th, the
absence of fossils of any kind lower down than the Cambrian strata.

Now all these objections depend on estimates of the imperfection of the
geological record much lower than that which is formed by Darwin.
Therefore I have arranged the objections in their order of difficulty in
this respect, or in the order that requires successively increasing
estimates of the imperfection of the record, if they are to be
successively answered.

I think that the first of them has been already answered in the text, by
showing that even a very moderate estimate of the imperfection of the
record is enough to explain why intermediate _varieties_, connecting
allied _species_, are but comparatively seldom met with. Moreover it was
shown that in some cases, where shells are concerned, remarkably
well-connected series of such varieties have been met with. And the same
applies to species and genera in certain other cases, as in the equine
family.

But no doubt a greater difficulty arises where whole groups of species
and genera, or even families and orders, appear to arise suddenly,
without anything leading up to them. Even this the second difficulty,
however, admits of being fully met, when we remember that in very many
cases it has been proved, quite apart from the theory of descent, that
superjacent formations have been separated from one another by wide
intervals of time. And even although it often happens that intermediate
deposits which are absent in one part of the world are present in
another, we have no right to assume that such is always the case.
Besides, even if it were, we should have no right further to assume that
the faunas of widely separated geographical areas were identical during
the time represented by the intermediate formation. Yet, unless they
were identical, we should not expect the fossils of the intermediate
formation, where extant, to yield evidence of what the fossils would
have been in this same formation elsewhere, had it not been there
destroyed. Now, as a matter of fact, "geological formations of each
region are almost invariably intermittent"; and although in many cases a
more or less continuous record of past forms of life can be obtained by
comparing the fossils of one region and formation with those of another
region and adjacent formations, it is evident (from what we know of the
present geographical distribution of plants and animals) that not a few
cases there must have been where the interrup