on, which occur in exactly the same way among
other animals or plants, to a principle, the ACTIVE INTERVENTION OF
WHICH IN THE TRANSFORMATION OF SPECIES IS NOWHERE PROVED. WE DO NOT
REQUIRE IT TO EXPLAIN THE FACTS, AND THEREFORE WE MUST NOT ASSUME IT.

The fact of coadaptation, which was supposed to furnish the strongest
argument against the principle of selection, in reality yields the
clearest evidence in favour of it. We MUST assume it, BECAUSE NO OTHER
POSSIBILITY OF EXPLANATION IS OPEN TO US, AND BECAUSE THESE ADAPTATIONS
ACTUALLY EXIST, THAT IS TO SAY, HAVE REALLY TAKEN PLACE. With this
conviction I attempted, as far back as 1894, when the idea of germinal
selection had not yet occurred to me, to make "harmonious adaptation"
(coadaptation) more easily intelligible in some way or other, and so
I was led to the idea, which was subsequently expounded in detail by
Baldwin, and Lloyd Morgan, and also by Osborn, and Gulick as ORGANIC
SELECTION. It seemed to me that it was not necessary that all the
germinal variations required for secondary variations should have
occurred SIMULTANEOUSLY, since, for instance, in the case of the
stag, the bones, muscles, sinews, and nerves would be incited by
the increasing heaviness of the antlers to greater activity in THE
INDIVIDUAL LIFE, and so would be strengthened. The antlers can only have
increased in size by very slow degrees, so that the muscles and bones
may have been able to keep pace with their growth in the individual
life, until the requisite germinal variations presented themselves. In
this way a disharmony between the increasing weight of the antlers and
the parts which support and move them would be avoided, since time would
be given for the appropriate germinal variations to occur, and so to set
agoing the HEREDITARY variation of the muscles, sinews, and bones.
("The Effect of 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,