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1859
1860
1861
1866
1869
1872

Compare with:
1859
1860
1861
1869
1872

in 1859 1860 1861 1866
to existing species in 1869 1872

will always 1859 1860 1861 1866
will of course 1869
would of course 1872

dog, 1859 1860 1861 1866 1869
case of the dog, 1872

must 1859 1860 1861 1866
in this latter respect must 1869 1872

quickly enough. 1859 1860 1861 1866 1869
still more quickly. 1872

sometimes 1859 1860 1861 1866 1869
easily err in 1872

which are really of very little importance, and which have originated from quite secondary causes, independently of 1859 1860 1861 1866
which have originated from quite secondary causes, independently of 1869
and in believing that they have been developed through 1872

should remember that climate, food, &c., probably have some little direct influence 1859 1860 1861 1866
should remember that climate, food, &c., probably have had some, perhaps a considerable, direct influence 1869
must by no means overlook the effects of the definite action of changed conditions of life,— of so-called spontaneous variations, which seem to depend in a quite subordinate degree 1872

organisation; that characters reappear from the 1859 1860 1861 1866 1869
nature of the conditions,— of the tendency to reversion to long-lost characters,— of the complex 1872

reversion; that correlation of growth will have had a most important influence in modifying various structures; 1859 1860 1861 1866
reversion; that correlation is an important element of change; 1869
growth, such as of correlation, compensation, of the pressure of one part on another, &c.,— 1872

will often have largely modified the external 1859 1860 1861 1866
has often largely modified the external 1869
by which 1872

animals having a will, to give one male an advantage in fighting with another or in charming the females. 1859 1860 1861 1866
the higher animals, so as to give one male an advantage in fighting with other males, or in charming the female; and characters gained through sexual selection may be transmitted to both sexes. 1869
use to one sex are often gained and then transmitted more or less perfectly to the other sex, though of no use to this sex. 1872

Moreover, when a modification of structure has primarily arisen from the above or other unknown causes, it may 1866
Moreover when a modification of structure has primarily arisen from the above or other unknown causes, it may 1859 1860 1861
Moreover a modification, caused in any of the above specified ways, may 1869
But structures thus indirectly gained, although 1872

advantage to the 1859 1860 1861 1866
direct advantage to a 1869
advantage to a 1872

the descendants of the species 1859 1860 1861 1866
its descendants 1869
its modified descendants, 1872

If 1859 1860 1861 1866 1872
If, for instance, 1869

former period, have been transmitted in nearly the same state, although now
become
become
of very slight use;
but
and
any actually injurious deviations in their structure will always have been checked by natural selection. Seeing how important an organ of locomotion the tail is in most aquatic animals, its general presence and use for many purposes in so many land animals, which in their lungs or modified swimbladders betray their aquatic origin, may perhaps be thus accounted for. A well-developed tail having been formed in an aquatic animal, it might subsequently come to be worked in for all sorts of
purposes,—
purposes,
as a fly-flapper, an organ of prehension, or as an aid in turning, as
in
with
the dog, though the aid must be slight, for the hare, with hardly any tail, can double quickly enough.
In the second place, we may sometimes
wrongly attribute
attributing
attribute
importance to
characters,
characters
which are really of very little importance, and which have originated from quite secondary causes, independently of natural selection. We should remember that climate, food, &c., probably have some little direct influence on the organisation; that characters reappear from the
laws
law
of reversion; that correlation of growth will have had a most important influence in modifying various structures; and
finally
finally,
of
that
sexual
selection,
selection
will often have largely modified the external characters of animals having a will, to give one male an advantage in fighting with another or in charming the females. Moreover, when a modification of structure has primarily arisen from the above or other unknown causes, it may at first
have been
have been
of no advantage to the species,
but
but
may subsequently have been taken advantage of by the descendants of the species under new conditions of life and
with
with
newly acquired habits.
To give a few instances to illustrate these latter remarks. If green woodpeckers alone had existed, and