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my theory will be strengthened; for we can clearly understand, on the principle of modification, why the inhabitants of a region should be related to those of another region, whence it has been stocked. 1859 1860 1861 1866
but are closely allied or belong to the same genera, if in all such cases it can be shown that there probably has been at some former period migration from the one region to the other, our general view will be much strengthened; for the explanation is obvious on the principle of descent with modification. 1869
though closely allied to them, it can be shown that migration from the one region to the other has probably occurred at some former period, our general view will be much strengthened; for the explanation is obvious on the principle of descent with modification. 1872

species in 1859 1860 1861 1866
the species of 1869 1872

(by substituting the word variety for species) 1859 1860 1861 1866
OMIT 1869 1872

in an ingenious paper 1859 1860 1861 1866
OMIT 1869 1872

in which he 1859 1860 1861 1866
who 1869 1872

species." 1859 1860 1866
species." 1861
species." And I now know that he attributes this coincidence to descent with modification. 1869
species." And it is now well known that he attributes this coincidence to descent with modification. 1872

previous remarks on "single and 1859 1860 1866
previous remarks on "single and 1861
discussion on "single and 1869
question of single or 1872

creation" do not directly bear on another 1859 1860 1866
creation" do not directly bear on another 1861
creation" does not directly bear on another 1869
creation differs from another though 1872

on my theory, must have 1859 1860 1861 1866
must be 1869 1872

which will never have 1859 1860 1861
which can never have 1866
which have supplanted each other, but which have never 1869
that have supplanted each other, but have never 1872

but will have supplanted each other; 1859 1860 1861 1866
of the same species; 1869 1872

each variety will have 1859 1860 1861 1866
the same variety will be 1869
the same form will be 1872

another
other
region, my theory will be strengthened; for we can clearly understand, on the principle of modification, why the inhabitants of a region should be related to those of another region, whence it has been stocked. A volcanic island, for instance, upheaved and formed at the distance of a few hundreds of miles from a continent, would probably receive from it in the course of time a few colonists, and their descendants, though modified, would still be
plainly
plainly
related by inheritance to the inhabitants of
that
the
continent. Cases of this nature are common, and are, as we shall hereafter
more fully
more fully
see, inexplicable on the theory of independent creation. This view of the relation of species in one region to those
of
in
another, does not differ much (by substituting the word variety for species) from that
lately
lately
advanced in an ingenious paper by Mr. Wallace, in which he
concludes
concludes,
that
"every
"every
species has come into existence coincident both in space and time with a pre-existing closely allied species." And I now know from correspondence, that this coincidence he attributes to generation with modification.
The previous remarks on "single and multiple centres of creation" do not directly bear on another allied question,—
namely,
namely
whether all the individuals of the same species
are
have
descended from a single pair, or single hermaphrodite, or whether, as some authors suppose, from many individuals simultaneously created. With
those
those
organic beings which never
intercross,
intercross
if
(if
such
exist,
exist),
each
the
species
species,
on my theory, must have descended from a succession of
modified
improved
varieties, which will never have blended with other individuals or
varie- ties,
varieties
varieties,
but will have supplanted each other; so that, at each successive stage of
modification,
modification
and improvement,
and improvement,
all the individuals of each variety will have descended from