I have now considered enough, perhaps more than enough, of the cases, selected with care by a skilful naturalist, to prove that natural selection is incompetent to account for the incipient stages of useful structures; and I have shown, as I hope, that there is no great difficulty on this head.

A good opportunity has thus been afforded for enlarging a little on gradations of structure, often associated with strange functions--an important subject, which was not treated at sufficient length in the former editions of this work.

I will now briefly recapitulate the foregoing cases.