DARWINISM AND EVOLUTION 43 



selection is, however, always essentially negative; 

 it is the survival of the fittest, and the underlying 

 reason for the presence of the fittest must be sought 

 elsewhere, ultimately in the interior laws regulating 

 the evolution of organic life. 



In this connection the theory of direct adaptation, 

 put forward by Lamarck and Nageli is of great use, 

 although it is only another way of stating the bene- 

 ficial capacity for reaction to external stimulus 

 which organisms possess. I believe that it is quite 

 impossible to avoid regarding the interior laws of 

 evolution as of primary importance, although I 

 gladly allow that it is difficult to work with unknown 

 causes. The exterior impulses governing evolution, 

 which are presented to us by means of plain 

 examples in Darwin's theory of selection, are very 

 attractive. As I showed you yesterday in speaking 

 of the inquilines among ants and termites, it is easy 

 to give many interesting examples of the exterior 

 conditions affecting evolution, but the exterior 

 factors could not be effective if they did not corre- 

 spond with the interior factors. The co-operation 

 of the interior and exterior factors is absolutely 

 necessary for any beneficial adaptation. If we do 

 not as yet know the interior factors of evolution, 

 that is a defect due to our imperfect scientific 

 knowledge ; we have only made a very humble 

 beginning towards investigating the causes of 

 organic evolution, but no one can lay the blame on 

 the theory of evolution, which is still in its infancy. 



