Darwin's Artificial and Natural Selection 155 
formed a serious stumbling-block to the theory of selection. 
Though still assuming that the przmary variations are ‘ acci- 
dental,’ I yet hope to have demonstrated that an interior 
mechanism exists which compels them to go on increasing in 
‘a definite direction, the moment selection intervenes. Defi- 
nitely directed variation exists, but not predestined variation, 
running on independently of the life conditions of the organ- 
ism, as Nageli, to mention the most extreme advocate of this 
doctrine, has assumed; on the contrary, the variation is such 
as is elicited and controlled by those conditions themselves, 
though indirectly.” 
“The real aim of the present essay is to rehabilitate the 
principle of selection. If I should succeed in reinstating this 
principle in its emperilled rights, it would be a source of 
extreme satisfaction to me; for I am so thoroughly convinced 
of its indispensability as to believe that its demolition would 
be synonymous with the renunciation of all inquiry concern- 
ing the causal relation of vital phenomena. If we could un- 
derstand the adaptations of nature, whose number is infinite, 
only upon the assumption of a teleological principle, then, I 
think, there would be little inducement to trouble ourselves 
about the causal connection of the stages of ontogenesis, for 
no good reason would exist for excluding teleological princi- 
ples from this field. Their introduction, however, is the ruin 
of science.’’} 
Weismann states that those critics who maintain that 
selection cannot create, but only reject, “fail to see that pre- 
cisely through this rejection its creative efficacy is asserted.” 
There is raised here, though not for the first time, a point 
that is of no small importance for both Darwinians and anti- 
Darwinians to consider; for, without further examination, it 
is by no means self-evident, as Weismann implies, that by 
exterminating all variations that are below the average the 
1 Translated by J. McCormack. The Open Court Publishing Company. The 
following quotations are also taken from this translation. 
