External Influences upon Development", Romanes Lecture, Oxford, 1894.)

I still regard this idea as correct, but I attribute less importance to
"organic selection" than I did at that time, in so far that I do not
believe that it ALONE could effect complex harmonious adaptations.
Germinal selection now seems to me to play the chief part in bringing about
such adaptations. Something the same is true of the principle I have
called "Panmixia". As I became more and more convinced, in the course of
years, that the LAMARCKIAN PRINCIPLE ought not to be called in to explain
the dwindling of disused parts, I believed that this process might be
simply explained as due to the cessation of the conservative effect of
natural selection. I said to myself that, from the moment in which a part
ceases to be of use, natural selection withdraws its hand from it, and then
it must inevitably fall from the height of its adaptiveness, because
inferior variants would have as good a chance of persisting as better ones,
since all grades of fitness of the part in question would be mingled with
one another indiscriminately. This is undoubtedly true, as Romanes pointed
out ten years before I did, and this mingling of the bad with the good
probably does bring about a deterioration of the part concerned. But it
cannot account for the steady diminution, which always occurs when a part
is in process of becoming rudimentary, and which goes on until it
ultimately disappears altogether. The process of dwindling cannot
therefore be explained as due to panmixia alone; we can only find a
sufficient explanation in germinal selection.

IV. DERIVATIVES OF THE THEORY OF SELECTION.

The impetus in all directions given by Darwin through his theory of
selection has been an immeasurable one, and its influence is still felt. It
falls within the province of the historian of science to enumerate all the