If it could be demonstrated that any complex organ existed, which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down. But I can find out no such case.
Authentication Score 2
Original Citation
Darwin, Charles. On the Origin of Species. London: John Murray, 1859, ch. 6.
Current Citation
Darwin, Charles. The Origin of the Species, edited by William Bynum. Penguin, 2009, ch. 6.