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natural 1859 1860 1861 1866 1869
variation and natural 1872

gradations in the perfection of any organ or instinct which we may consider, either do now exist or could have existed, each good of its kind,— that all organs 1860
gradations in the perfection of any organ or instinct, which we may consider, either do now exist or could have existed, each good of its kind,— that all organs 1859
all organs 1861 1866
all parts of the organisation 1869 1872

are, in ever so slight a degree, variable,— and, lastly, 1859 1860
are, in ever so slight a degree, variable— 1861 1866
offer, at least, individual differences— 1869 1872

instinct. 1859 1860
instinct— and, lastly, that gradations in the perfection of every organ may have existed, each good of its kind. 1861 1866
instinct— and, lastly, that gradations in the state of perfection of each organ may have existed, each good of its kind. 1869 1872

CHAPTER
XV.
XIV.
RECAPITULATION AND CONCLUSION.
Recapitulation of the
objections to
difficulties on
the theory of Natural Selection— Recapitulation of the general and special circumstances in its
favour.—
favour—
Causes of the general belief in the immutability of species— How far the theory of
Natural
natural
Selection
selection
may be extended— Effects of its adoption on the study of Natural
History—
history—
Concluding remarks.
As
AS
this whole volume is one long argument, it may be convenient to the reader to have the leading facts and inferences briefly recapitulated.
That many and
grave
serious
objections may be advanced against the theory of descent with modification through natural selection, I do not deny. I have endeavoured to give to them their full force. Nothing at first can appear more difficult to believe than that the more complex organs and instincts
should
should
have been perfected, not by means superior to, though analogous with, human reason, but by the accumulation of innumerable slight variations, each good for the individual possessor. Nevertheless, this difficulty, though appearing to our imagination insuperably great, cannot be considered real if we admit the following propositions,
namely,
namely,—
that gradations in the perfection of any organ or instinct which we may consider, either do now exist or could have existed, each good of its kind,— that all organs and instincts are, in ever so slight a degree, variable,— and, lastly, that there is a struggle for existence leading to the preservation of
each
each
profitable
deviations
deviation
of structure or instinct. The truth of these propositions cannot, I think, be disputed.