Origin of Species Variorum

Comparison with 1861

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.

Text in this page (from paragraph 3300, sentence 101 to paragraph 3300, sentence 130, word 25) is not present in 1861

those which have become extinct, the difficulty ceases to be very great (not more so than in the case of many other structures) in believing that natural selection may have converted the simple apparatus of an optic nerve, .. 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 should find on finishing this volume that large bodies of facts, otherwise inexplicable, can be explained by the theory of descent with modification, ought not to hesitate to go further, and to admit that a structure even as perfect as the eye of an eagle might have been formed by natural selection, although in this case he does not know .. the transitional steps. ↑ Even in the Vertebrata, so manifestly the most highly organized division of the animal kingdom, we can start, as in the former cases, from an eye, such as exists in the fish called the lancelet, which is so simple that it consists only of a little fold-like sack of skin, lined with pigment and furnished with a nerve, but destitute of any other apparatus, being merely covered by transparent membrane. In the class both of fishes and reptiles, as Owen has remarked, "the range of gradations of dioptric structures is very great." It is a significant fact that even in man, according to the high authority of Virchow, the beautiful crystalline lens is originally formed merely by an accumulation of cells of the epidermis, lying in a sack-like fold of the skin; and the vitreous body is formed from embryonic sub-cutaneous tissue. It is indeed indispensable that the naturalist who reflects on the origin and manner of formation of the eye, with all its marvellously perfect attributes, should make his reason conquer his imagina- tion; though