SELECTION 145 



as it was to biological specialists before 1858. 

 But that suggestion is the central idea of the 

 ' Origin of Species,' and contains the quint- 

 essence of Darwinism. . . . That which we 

 were looking for, and could not find, was an 

 hypothesis respecting the origin of known 

 organic forms which assumed the operation 

 of no causes but such as could be proved 

 to be actually at work. We wanted, not to 

 pin our faith to that or any other speculation, 

 but to get hold of clear and definite concep- 

 tions which could be brought face to face with 

 facts and have their validity tested. The 

 * Origin ' provided us with the working 

 hypothesis we sought. ..." 



Of " the quintessence of Darwinism," then, 

 a brief account is needed, and this may be 

 best given by following as closely as possible 

 upon the lines of the magnum opus itself, 

 although the full title of this" The Origin 

 of Species by means of Natural Selection, or the 

 Preservation of Favoured Races in the Struggle 

 for Life," is its own best and briefest summary, 



ANALYSIS OF " THE ORIGIN OF SPECIES." 

 After mentioning that his first light upon the 

 origin of species was derived from his early 

 distributional studies, Darwin points out that 

 " a naturalist, reflecting on the mutual affini- 

 ties of organic beings, on their embryological 



