My favorite quote from the renowned charlatan showing the above is his treatment of the eye:
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. 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.
From: Origin of the Species, Chapter 6
He is blatantly telling his readers that if they have put up with his drivel for hundreds of odd pages this nonsense should be no problem!
Your favorite out of context quote I might add. Here is the rest of it.