| ↑ 1 blocks not present in 1866 1869; present in 1859 1860 1861 1872 |
| 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 such
startling lengths.
|
|
| → spaces filled with fluid, and with a 1861 1866 1869 1872 |
| a 1859 1860 |
|
| → (natural selection) always 1861 1866 |
| always 1859 1860 |
| represented by natural selection or the survival of the fittest, always 1869 1872 |
|
|
I have felt
difficulty far too keenly to be surprised at any degree of hesitation in extending the principle of natural selection to so startling a length. ↑
|
|
| It is scarcely possible to avoid comparing the eye
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
→spaces filled with fluid, and with a
nerve sensitive to light beneath, and then suppose every part of this layer to be continually changing slowly in density, so as to separate into layers of different densities and thicknesses, placed at different distances from each other, and with the surfaces of each layer slowly changing in form. Further we must suppose that there is a
→(natural selection) always
intently watching each slight
alteration in the transparent layers; and carefully
each
which, under varied circumstances,
in any
or in any degree,
to produce a distincter image. We must suppose each new state of the instrument to be multiplied by the million;
each to be preserved
a better
produced, and then the old ones to be
In living bodies, variation will cause the slight alterations, generation will multiply them almost infinitely, and natural selection will pick out with unerring skill each improvement. Let this process go on for millions
of years; and during each year on millions of individuals of many kinds; and may we not believe that a living optical instrument might thus be formed as
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