Chapter VII

. of the 'Origin' (1st edition). It thus forms a complement to the chapters which deal with variation in structure. It seems to have been placed thus early in the Essay to prevent the hasty rejection of the whole theory by a reader to whom the idea of natural selection acting on instincts might seem impossible. This is the more probable, as the Chapter on Instinct in the 'Origin' is specially mentioned (Introduction, page 5) as one of the "most apparent and gravest difficulties on the theory." Moreover the

## chapter in the Sketch ends with a discussion, "whether any particular

corporeal structures...are so wonderful as to justify the rejection prima facie of our theory." Under this heading comes the discussion of the eye, which in the 'Origin' finds its place in