| Comparison with 1860 |
|
|
and must act by convergence; and at their lower ends there seems to be an imperfect vitreous substance. With
these facts, here far
too 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 has
converted the simple apparatus of an optic nerve
merely
coated with pigment and invested by transparent membrane, into an optical instrument as perfect as is possessed by any member of the great
Articulate class.
|
|
He who will go thus far, if
he find
on finishing this 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 eagle
might
be
formed
by natural selection,
although in this case he does not know any of
the transitional grades.
↑| 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.
|
|
|
| It is scarcely possible to avoid comparing the eye 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
|
and must act by convergence; and at their lower ends there seems to be an imperfect vitreous substance.
With | With 1859 1860 1861 |
| When we reflect on 1866 1869 1872 |
| far 1859 1860 | | given 1866 1869 | | given much 1872 | far 1861 |
| briefly 1859 1860 1861 1866 | | briefly, 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 |
| has 1859 1860 1861 | | may have 1866 1869 1872 |
| nerve 1859 1860 1861 | | nerve, 1866 1869 1872 |
| merely 1859 1860 1861 | merely 1866 1869 1872 |
| great 1859 1860 1861 1866 1869 | great 1872 |
| class. 1859 1860 1861 | | Class. 1866 1869 1872 |
|
|
He who will go thus far,
if | if 1859 1860 1861 1866 |
| ought not to hesitate to go one step further, if 1869 1872 |
| find 1859 1860 1861 | | should find 1866 | | finds 1869 1872 |
| treatise 1859 1860 1861 | | volume 1866 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 |
| eagle 1859 1860 1861 1866 | | eagles 1869 | | eagle's 1872 |
| might 1859 1860 1861 1866 |
| eye might 1869 |
| eye might thus 1872 |
| be 1859 1860 1861 1869 1872 | | have been 1866 |
| formed 1859 1860 1861 1866 1869 | | formed, 1872 |
| by natural selection, 1859 1860 1861 1866 1869 |
| OMIT 1872 |
| any of 1859 1860 1861 | any of 1866 1869 1872 |
| grades. 1859 1860 1861 | | steps. 1866 | | states. 1869 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 |
| such 1859 1860 1861 | | so 1872 |
| lengths. 1859 1860 1861 | | a length. 1872 |
|
|
It is scarcely possible to avoid comparing the eye
to | to 1859 1860 1861 1866 | | with 1869 1872 |
| a 1859 1860 |
| spaces filled with fluid, and with a 1861 1866 1869 1872 |
|
