HISTORY OF THE THEORY OF EVOLUTION 17 



that principles were determined competent to account 

 for the changes in all past time, and the death-blow 

 given to Cuvier's views. 



Evidence as to the reality of Evolution was now 

 rapidly accumulating, not only through the work 

 and writings of those already mentioned, but from 

 many other sides. Professor Huxley in 1859 

 refers to the hypothesis that species living at any 

 time are the result of the gradual modification of 

 pre-existing species, as the "only one to which 

 physiology lends any countenance." Sir Joseph 

 Hooker in 1859, in his "Introduction to the 

 Australian Flora," admits the truth of descent and 

 modification of species, and. supports the doctrine by 

 many original observations. 



Herbert Spencer's essay in the Leader, 1852, 

 constitutes "the high-water mark" of Evolution 

 prior to Darwin : " Even could the supporters of the 

 development hypothesis merely show that the pro- 

 duction of species by the process of modification is 

 conceivable, they would be in a better position than 

 their opponents. But they can do much more than 

 this ; they can show that the process of modification 

 has effected and is effecting great changes in all 



organisms subject to modifying influences 



They can show that any existing species — animal or 

 vegetable — when placed under conditions different 

 from its previous ones, immediately begins to under- 

 go certain changes of structure fitting it for the new 

 conditions. They can show that in successive 

 generations these changes continue until ultimately 

 the new conditions become the natural ones. They 



