THE HISTORY OF OUR SPECIES. 79 



simple principle of continuity found no one to apply 

 it to the organic world. The rudiments of a natural 

 phylogeny which were buried in Lamarck's works 

 were as completely forgotten as the germ of a natural 

 ontogeny which Caspar Friedrich Wolff had given 

 fifty years earlier in his Theory of Generation. In 

 both cases a full half century elapsed before the great 

 idea of a natural development won a fitting recogni- 

 tion. Only when Darwin (in 1859) approached the 

 solution of the problem from a different side 

 altogether, and made a happy use of the rich 

 treasures of empirical knowledge which had accumu- 

 lated in the meantime, did men begin to think once 

 more of Lamarck as his great precursor. 



The unparalleled success of Charles Darwin is well 

 known. It shows him to-day, at the close of the 

 century, to have been, if not the greatest, at least the 

 most effective, of its distinguished scientists. No 

 other of the many great thinkers of our time has 

 achieved so magnificent, so thorough, and so far- 

 reaching a success with a single classical work as 

 Darwin did in 1859 with his famous Origin of Species. 

 It is true that the reform of comparative anatomy and 

 physiology by Johannes Midler had inaugurated a 

 new and fertile epoch for the whole of biolog}^ ; that 

 the establishment of the cellular theory by Schleiden 

 and Schwann, the reform of ontogeny by Baer, and 

 the formulation of the law of substance by Robert 

 Mayer and Helmholz, were scientific facts of the first 

 importance ; but no one of them has had so profound 

 an influence on the whole structure of human knowledge 

 as Darwin's theory of the natural origin of species. 

 For it at once gave us the solution of the mystic 

 " problem of creation," the great " question of all 



