See page in:
1859
1860
1861
1866
1869
1872

Compare with:
1859
1861
1866
1869
1872

With 1859 1860 1861
When we reflect on 1866 1869 1872

and imperfectly given, which show that there is much graduated diversity 1859 1860
and imperfectly given, which show how much graduated diversity 1861
and imperfectly, with respect to the wide, diversified, and graduated range of structure 1866
with respect to the wide, diversified, and graduated range of structure 1869 1872

in 1859 1860 1866 1869 1872
there is in 1861

living crustaceans, and bearing 1859 1860
our existing crustaceans, and bearing 1861
the existing Articulata; and when we bear 1866
the lower animals; and when we bear 1869 1872

living animals is in proportion to 1859 1860 1861
all living forms must be in comparison with 1866 1872
all the forms now living must be in comparison with 1869

I can see no 1859 1860 1861
the difficulty ceases to be 1866 1869 1872

difficulty (not more than in the case of many other structures) 1859 1860 1861
(not more so than in the case of many other structures) 1866
OMIT 1869 1872

if 1859 1860 1861 1866
ought not to hesitate to go one step further, if 1869 1872

descent, ought not to hesitate to go further, and 1859 1860 1861
descent with modification, ought not to hesitate to go further, and 1866
descent with modification; he ought 1869
modification through natural selection; he ought 1872

the eye of 1859 1860 1861 1866
OMIT 1869 1872

might 1859 1860 1861 1866
eye might 1869
eye might thus 1872

by natural selection, 1859 1860 1861 1866 1869
OMIT 1872

1 blocks not present in 1859 1860 1861 1866; present in 1869 1872
It has been objected that in order to modify the eye and still preserve it as a perfect instrument, many changes would have to be effected simultaneously, which, it is assumed, could not be done through natural selection; but as I have attempted to show in my work on the variation of domestic animals, it is not necessary to suppose that all the modifications were simultaneous, if they were extremely slight and gradual.

His reason ought to conquer his imagination; though 1859 1860 1861
To arrive, however, at a just conclusion regarding the formation of the eye, with all its marvellous yet not absolutely perfect characters, it is indispensable that the reason should conquer the imagination; but 1872

any degree of hesitation in extending 1859 1860 1861
others hesitating to extend 1872

a 1859 1860
spaces filled with fluid, and with a 1861 1866 1869 1872

With these facts, here
given
given much
far
far
too
briefly,
briefly
and imperfectly given, which show that there is much graduated diversity in the eyes of living crustaceans, and bearing in mind how small the number of living animals is in proportion to those which have become extinct, I can see no very great difficulty (not more than in the case of many other structures) in believing that natural selection
may have
has
converted the simple apparatus of an optic
nerve,
nerve
merely
merely
coated with pigment and invested by transparent membrane, into an optical instrument as perfect as is possessed by any member of the
great
great
Articulate
Class.
class.
He who will go thus far, if he
should find
finds
find
on finishing this
volume
treatise
that large bodies of facts, otherwise inexplicable, can be explained by the theory of descent, ought not to hesitate to go further, and to admit that a structure even as perfect as the eye of an
eagles
eagle's
eagle
might
have been
be
formed,
formed
by natural selection, although in this case he does not know
any of
any of
the transitional
steps.
states.
grades.
His reason ought to conquer his imagination; though I have felt the difficulty far too keenly to be surprised at any degree of hesitation in extending the principle of natural selection to
so
such
startling
a length.
lengths.
It is scarcely possible to avoid comparing the eye
with
to
a telescope. We know that this instrument has been perfected by the long-continued efforts of the highest human intellects; and we naturally infer that the eye has been formed by a somewhat analogous process. But may not this inference be presumptuous? Have we any right to assume that the Creator works by intellectual powers like those of man? If we must compare the eye to an optical instrument, we ought in imagination to take a thick layer of transparent tissue, with a nerve sensitive to light beneath, and then suppose every part of this layer to be continually changing