e become extinct; and carriers
which are extreme in the important character of length of beak originated
earlier than short-beaked tumblers, which are at the opposite end of the
series in this same respect.

Closely connected with the statement, that the organic remains from an
intermediate formation are in some degree intermediate in character, is the
fact, insisted on by all palaeontologists, that fossils from two consecutive
formations are far more closely related to each other, than are the fossils
from two remote formations. Pictet gives as a well-known instance, the
general resemblance of the organic remains from the several stages of the
Chalk formation, though the species are distinct in each stage. This fact
alone, from its generality, seems to have shaken Professor Pictet in his
firm belief in the immutability of species. He who is acquainted with the
distribution of existing species over the globe, will not attempt to
account for the close resemblance of the distinct species in closely
consecutive formations, by the physical conditions of the ancient areas
having remained nearly the same. Let it be remembered that the forms of
life, at least those inhabiting the sea, have changed almost simultaneously
throughout the world, and therefore under the most different climates and
conditions. Consider the {336} prodigious vicissitudes of climate during
the pleistocene period, which includes the whole glacial period, and note
how little the specific forms of the inhabitants of the sea have been
affected.

On the theory of descent, the full meaning of the fact of fossil remains
from closely consecutive formations, though ranked as distinct species,
being closely related, is obvious. As the accumulation of each formation
has often been interrupted, and as long blank intervals have intervened
between successive formations, we ought not to expect to find, as I
attempted to show in the last chapter, in any one or two formations all the
intermediate varieties between the species which appeared at the
commencement and close of these periods; but we ought to find after
intervals, very long as measured by years, but only moderately long as
measured geologically, closely allied forms, or, as they have been called
by some authors, representative species; and these we assuredly do find. We
find, in short, such evidence of the slow and scarcely sensible mutation of
specific forms, as we have a just right to expect to find.