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their ancient homes, as they would differ from their former
in a nearly uniform, though perhaps extremely slight degree,
→and as they would be found embedded in slightly different sub-stages of the same formation, they
would, according to the principles followed by many palæontologists, be ranked as new and distinct species. |
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| If
there be some degree of truth in these remarks, we have no right to expect to
in our geological formations, an infinite number of those fine transitional
on
have connected all the past and present species of the same group into one long and branching chain of life. We ought only to look for a few links,
→and such assuredly we do find—
some more
→some more closely, related
to each other; and these links, let them be ever so close, if found in different stages of the same formation, would, by
be ranked as distinct species. But I do not pretend that I should ever have suspected how poor
→was the record in
the best
geological
had not the
of
→OMIT
innumerable transitional links between the species which
at the commencement and close of each formation, pressed so hardly on my theory. |
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| The abrupt manner in which whole groups of species suddenly appear in certain formations, has been urged by several
for instance, by Agassiz, Pictet, and
→Sedgwick—
as a fatal objection to the belief in the transmutation of species. If numerous species, belonging to the same genera or families, have really started into life
at once, the fact would be fatal to the theory of
→evolution
through natural selection. For the development
→by this means of
a group of forms, all of which
descended from some one progenitor, must have been an extremely slow process; and the
must have lived long
before their modified descendants. But we continually
the perfection of the geological record, and falsely infer, because certain genera or families have not been found beneath a certain stage, that they did not exist before that stage. In all cases positive palæontological evidence may be implicitly trusted; negative evidence is worthless, as experience has so often shown. 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
and have slowly
before they invaded the ancient archipelagoes of Europe and
the United States. We do not make due allowance for the
intervals of
which have
elapsed between our
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