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.
One hundred and twenty five years on, we know a lot more about animals and plants than Darwin did, and still not a single case is known to me of a complex organ that could not have been formed by numerous successive slight modifications. I do not believe that such a case will ever be found. If it is - it'll have to be a really complex organ, and, as we'll see elsewhere, you have to be sophisticated about what you mean by 'slight' - I shall cease to believe in Darwinism.
