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1859
1860
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1869
1872

variation 1859 1860 1861 1866
acknowledged variations 1869
the production of varieties 1872

so-called specific forms. 1859 1860 1861 1866
so-called specific differences. 1869
distinct species. 1872

but little direct effect; yet when varieties enter any zone, they occasionally assume some of the characters of the species proper to that zone. 1859 1860 1861 1866
some direct and definite effect, but how much we cannot say. 1869 1872

1 blocks not present in 1859 1860 1861 1866; present in 1869 1872
Thus when varieties enter any new station, they occasionally assume some of the characters proper to the species of that station.

hybrids! 1859 1860 1861 1866 1869
hybrids! How simply is this fact explained if we believe that these species are all descended from a striped progenitor, in the same manner as the several domestic breeds of the pigeon are descended from the blue and barred rock-pigeon! 1872

pigeon have 1859 1860 1861 1866
the pigeon are 1869

the
living
live
bodies of caterpillars;
or
and
at other such cases. The wonder indeed is, on the theory of natural selection, that more cases of the want of absolute perfection have not been
detected.
observed.
The complex and little known laws governing variation are the same, as far as we can
judge,
see,
with the laws which have governed the production of so-called specific forms. In both cases physical conditions seem to have produced but little direct effect; yet when varieties enter any zone, they occasionally assume some of the characters of the species proper to that zone.
With
In
both varieties and species, use and disuse seem to have produced
a considerable
some
effect; for it is
impossible
difficult
to resist this
con-
....
clusion
conclusion
when we look, for instance, at the logger-headed duck, which has wings incapable of flight, in nearly the same condition as in the domestic duck; or when we look at the burrowing
tucu-tucu,
tucutucu,
which is occasionally blind, and then at certain moles, which are habitually blind and have their eyes covered with skin; or when we look at the blind animals inhabiting the dark caves of America and Europe.
In
With
In both
varieties and
species,
species
correlated
correlation
variation
of growth
seems to have played
an
a most
important part, so that when one part has been modified other parts
have been
are
necessarily modified.
With
In
both varieties and
species,
species
reversions to long-lost characters
occasionally occur.
occur.
How inexplicable on the theory of creation is the
occasional
variable
appearance of stripes on the
shoulders
shoulder
and legs of the several species of the horse-genus and
of
in
their hybrids! How simply is this fact explained if we believe that these species
are all
have
all descended
descended
from a striped progenitor, in the same manner as the several domestic breeds of pigeon have descended from the blue and barred rock-pigeon!
On the ordinary view of each species having been independently created, why should
the
the
specific
characters,
charac- ters,