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 pal ontologists, 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 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.
_On the state of Development of Ancient Forms_. There has been much
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