1 2 ANT I GIF A TION AND INTERPRE TA TION OF NA 7 URh . 



tion established. Observation and speculation upon 

 other factors of Evolution. 



No sharp lines actually separated these periods ; 

 each passed gradually into the next. The decline 

 of Greek, and especially of Aristotelian influence 

 in natural science, was extremely gradual, and was 

 overlapped by the awakening of the spirit of origi- 

 nal research upon animals and plants, and of the 

 science of medicine. Similarly, what we may call 

 the Philosophers' period ran insensibly into the 

 Buffon or third period, for the later naturalists 

 began their work contemporaneously with the later 

 philosophers. Perhaps the sharpest transition was 

 at the close of the third period, in which a distinct 

 anti-Evolution school had sprung up and succeeded 

 in firmly entrenching itself, so that Darwin and 

 Wallace began the present era with some ab- 

 ruptness. 



ENVIRONMENT OF THE EVOLUTION IDEA. 



As we have seen in this resume, the idea had 

 a long struggle for growth and existence in the 

 twenty-four centuries between Thales and Darwin, 

 yet it never wholly suspended animation. I may 

 emphasize again the standpoint of these lectures, 

 that the final conception of Evolution is to be 

 regarded as a cluster of many subsidiary ideas, 

 which slowly evolved in the environment of advan- 

 cing human knowledge. Like an animal or plant, 



