president's address. 825 



It will be observed that in both of these hypotheses thus 

 presented there is presupposed the principle of continuity or 

 uniformity in Nature, which indeed lies at the root of every 

 application of the histoiical method of interpretation. The 

 negative attitude assumed by Cuvier, the great founder of 

 palaeontology, towards the entire theory of mutability is, of 

 course, to be correlated with his advocacy of periodic extinction 

 of types and of catastrophic geological hypotheses generally. 



The uniformitarian principle was most strongly upheld by 

 Lamarck, and, though for a time it was relegated to the back- 

 ground by the great authority of Cuvier, it once more, and finally, 

 reassei-ted itself convincingly in Lyell's Principles of Geology in 

 1830. From the triumph of uniformitarianism the reassertion of 

 the somewhat discredited evolutionary principle was almost a 

 necessary consequence. Yet Lyell himself was a professed 

 agnostic as to the natural causes determining the successive 

 appearance of new forms; and none of the immediate evolutionist 

 precursors of Darwin were able to add anything new to the discus- 

 sion of the probable factors and conditions of the process they 

 were disposed to advocate. 



The part played by the Darwinian conception of natural selec- 

 tion in gaining for the evolution doctrine a practically universal 

 acceptance in the thought of this century, is too familiar to allow 

 of my pressing it on your attention at any length. 



It provided, for would-be evolutionists, that basis of natural 

 causation in organic transformation, the absence of which from 

 the earlier evolutionary theories explains their inability to rise 

 above the almost purel}' speculative stage. Thus, if we take 

 such speculative evolutionism in perhaps its most striking 

 literary expression, we may recognise in the pregnant thought of 

 Goethe a strong and confident conviction of a unity of type and 

 of a "shaping principle which works underground in Nature." 

 For him these were patent and operative principles, and proofs 

 of actual community of origin amongst organic forms. Yet his 

 suggestive biological ideas were unal^le to reach the condition of 

 acknowledged scientific certainty in the absence of such a theory 



