4io
variations are not accidental, this shows that they have
not occurred among variations inevitably associated with
sexual reproduction. If the change is due to the sensitive
response of the organism, acted upon by external con
ditions, these are not the variations from which Natural
Selection professes to select. With respect to the relative
part which Natural Selection plays in comparison with the
direct action of the environment, it is obvious, to say the
least, that the more there is done by external condition,
the less will be left to do by Natural Selection. How
selection can act on forms best capable of responding to the
requirements of new conditions—if that means a mere
potency, and not an actually achieved change, more or less
—appears to me utterly inconceivable.
A third test is based upon the utility of the variation.
Mr. Darwin declares that transforming influences produce
useless variations and cannot produce useful variations
in face of changed conditions. On the other hand, he
contends that Natural Selection cannot produce useless
variations, but that all useful variations are the result of its
action. But, at the same time, he warns us that it is not
always easy to say how much is due to Natural Selection,
or how much to transforming influence.
Mr. Darwin frequently insists on the fact that trans
forming influences produce unuseful variations.
“No doubt the definite action of changed conditions and the
various causes of modifications, lately specified, have all produced an
effect—probably a great effect—independently of any advantage.”—
(Origin of Species, p. 160.)
“ In many other cases modifications are probably the direct result of
the laws of variation or of growth, independently of any good
having been thus gained.”—(Origin of Species, pp. i6y-6.)
“As these variations seem of no special use to the plants, they
cannot have been influenced by Natural Selection.”—(Origin of
Species, p. 174.)