384 EVOLUTION, OLD AND NEW. 



Selection, by the same constant interaction of Adapta- 

 tion and Heredity [what is Heredity but another word 

 for unknown causes, unless it is explained in some sucli 

 manner as in ( Life and Habit ' ?] by which all the other 

 purposive contrivances of the animal organization have 

 been slowly and gradually evolved during the struggle 

 for existence." 



I see no evidence for " premeditated aim " at any 

 modification very far in advance of an existing organ, 

 any more than I do for " premeditated aim " on man's 

 part at any as yet inconceivable mechanical invention ; 

 but as in the case of man's inventions, so also in that 

 of the organs of animals and plants, modification is due 

 to the accumulation of small, well-considered improve- 

 ments, as found necessary in practice, and the conduct 

 of their affairs. Each step having been purposive, 

 the whole road has been travelled purposively ; nor is 

 the purposiveness of such an organ, we will say, as the 

 eye, barred by the fact that invention has doubtless 

 been aided by some of those happy accidents which 

 from time to time happen to all who keep their wits 

 about them, and know how to turn the gifts of Fortune 

 to account. 



