Darwin s Artificial and Natural Selection 155 



formed a serious stumbling-block to the theory of selection. 

 Though still assuming that the primary variations are ' acci- 

 dental,' I yet hope to have demonstrated that an inte r ior 

 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 yariation, 

 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." 



" Thereat~aTm 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 t rouble ourselves 

 about the causal connection of the stages (6fontogenesis) for 

 no good reason would exist for excluding teleological p rinci- 

 ples from this field. Their introduction, however, is the ruin 

 ot science." 1 



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. 



