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in that district and amongst these species, 1861 1866 1869 1872
there, on an average, 1859 1860

on an average, most varieties. 1861 1866 1869 1872
most varieties or incipient species. 1859 1860

long-continued 1859 1860 1861 1866 1872
long - continued 1869

may readily have 1859 1860 1861 1866
has 1869 1872

variation and differentiation, or where the manufactory of new specific forms has been actively at
work —
work—
in that district and amongst these species, we now
find
find,
on an average, most varieties. Secondary sexual characters are highly variable, and such characters differ much in the species of the same group. Variability in the same parts of the organisation has generally been taken advantage of in giving secondary sexual differences to the
two sexes
sexes
of the same species, and specific differences to the several species of the same genus. Any part or organ developed to an extraordinary size or in an extraordinary manner, in comparison with the same part or organ in the allied species, must have gone through an extraordinary amount of modification since the genus arose; and thus we can understand why it should often still be variable in a much higher degree than other parts; for variation is a long-continued and slow process, and natural selection will in such cases not as yet have had time to overcome the tendency to further variability and to reversion to a less modified state. But when a species with any extraordinarily-developed organ has become the parent of many modified
descendants —
descendants—
which on
our
my
view must be a very slow process, requiring a long
laps
lapse
of
time —
time—
in this case, natural selection may readily have succeeded in giving a fixed character to the organ, in however extraordinary a manner it may
have been
be
developed. Species inheriting nearly the same constitution from a common
parent,
parent
and exposed to similar
influences,
influences
will
will
naturally tend to present analogous variations,
or
and
these same species may occasionally revert to some of the characters of their ancient progenitors. Although new and important modifications may not arise from reversion and analogous
varia- tion,
variation,
such modifications will add to the beautiful and harmonious diversity of nature.