692 Studies in the Theory of Descent. 



both cases very far from being complete, and still 

 contains large and numerous gaps.- 8 



The theoretical conception of variation as the 

 reaction of the organism to external influences 

 has also not yet been experimentally shown to be 

 correct. Our experiments are still too coarse 

 as compared with the fine distinctions which 

 separate one individual from another ; and the 

 difficulty of obtaining clear results is greatly in- 

 creased by the circumstance that a portion of 

 the individual deviations always depends upon 

 heredity, so that it is frequently not only difficult, 

 but absolutely impossible, to separate those which 

 are inherited from those which are acquired. 

 Still further are we removed from being able to 

 refer variation to its final mechanical causes, i.e. 

 from a mechanical theory of reproduction, which 

 would bring within the range of mathematical 

 calculation both the phenomena of stability 

 (heredity) and of change (variability). 



But although sufficient proofs of the correct- 

 ness of the views here advocated cannot at 

 present be adduced, these views are not contra- 

 dicted by any known facts they are, on the 

 contrary, supported by many facts which they in 

 tun? make comprehensible (local forms, different 



18 [Eng. ed. Meanwhile it has been shown by Oscar Schmidt 

 that Von Hartmann, under the name of " the Unconscious," re- 

 invests the old vital force with some portion of its former 

 power. " Die naturwissenschaftlichen Grundlagen der Phi- 

 losophic des Unbewussten," Leipzig, 1877, p. 41.] 



