138 CHARLES DARWIN. 



sufficiently evidenced by palaeontology ; and I remain of the 

 opinion expressed in the second, that until selective breeding 

 is definitely proved to give rise to varieties infertile with one 

 another, the logical foundation of the theory of natural 

 selection is incomplete." 



It is therefore clear, as I have before stated, 

 that Huxley, in 1893, re-stated his criticisms and 

 quahfications of thirty years before, and expressed 

 his conviction anew of the vahdity of the objections 

 which he then raised against a full and complete 

 acceptance of natural selection. 



We now come to the last and most significant 

 of all Huxley's utterances on evolution and natural 

 selection, made on two great occasions in the last 

 year of his life. Lord Salisbury, in his eloquent 

 and interesting Presidential Address to the British 

 Association at Oxford (August 8th, 1894), had said 

 of Darwin : — 



" He has, as a matter of fact, disposed of the doctrine of the 

 immutability of species. . . . Few now are found to doubt 

 that animals separated by differences far exceeding those that 

 distinguish what we know as species have yet descended from 

 common ancestors." 



While thus completely admitting evolution in the 

 organic world, Lord Salisbury attacked natural 

 selection on two grounds — first, on the insufficiency 

 of the time allowed by physicists for a process which 

 is, of necessity, extremely slow in its operation; 

 secondly, on the ground that " we cannot demonstrate 

 the process of natural selection in detail ; we cannot 



