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or some few 1859 1860 1861 1866 1869
OMIT 1872

groups of species 1861 1866 1869
species 1859 1860
groups or species 1872

and consequently that the transitional forms would often long remain confined to some one region; but 1861 1866 1869 1872
but 1859 1860

adaptation had once 1861 1866 1869 1872
had 1859 1860

be able to 1859 1860 1861 1866
OMIT 1869 1872

of forms, all of which
are
have
descended from some one progenitor, must have been an extremely slow process; and the
progenitors,
progenitors
must have lived long
ages
ages
before their modified descendants. But we continually
over-rate
overrate
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
existed
existed,
and have slowly
multiplied
multiplied,
before they invaded the ancient archipelagoes of Europe and
of
....
the United States. We do not make due allowance for the
enormous
enormous
intervals of
time,
time
which have
probably
....
elapsed between our consecutive formations,— longer perhaps in
some
most
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 or some few
parent-form:
parent-forms;
and in the succeeding
formation,
formation
such groups of species will appear as if suddenly created.
I may here recall a remark formerly made,
namely
namely,
that it might require a long succession of ages to adapt an organism to some new and peculiar line of life, for
instance
instance,
to fly through the air; and consequently that the transitional forms would often long remain confined to some one region; but
that
that,
when this adaptation had once been effected, and a few species had thus acquired a great advantage over other organisms, a comparatively short time would be necessary to produce many divergent forms, which would be able to spread rapidly and widely throughout the world. Professor Pictet, in his