COLLECTION OF NOTES. 43 



of any naturalist who should attempt to supply a motive 

 force for evolution. And he regarded the previous 

 attempts at an explanation — the direct action of sur- 

 roundings and the will of the organism — as inadequate 

 because they could not account for such adaptations. 



Therefore being convinced of evolution, but as yet 

 unprovided with a motive cause which in any way 

 satisfied him, he began in July, 1837,, shortly after his 

 return home from the Beagle, to collect all facts which 

 bore upon the modifications which man has induced in 

 the animals and plants which he has subjugated, fol- 

 lowing, as he tells us, the example of Lyell in geology. 

 He goes on to say in his " Autobiography " : — 



" I soon perceived that selection was the key-stone of man's 

 success in making useful races of animals and plants. But 

 how selection could be applied to organisms living in a state of 

 nature remained for some time a mystery to me." 



We see indications in the extracts from his note- 

 book at this period (viz. between July, 1837, and 

 February, 1838), and before he had arrived at the 

 conception of Natural Selection, that he had the idea 

 of " laws of change " affecting species to some extent 

 like the laws of change which compel the individuals 

 of every species to work out their own development, 

 the extinction of the one corresponding in a measure 

 to the death of the other. Thus he says, " It is a won- 

 derful fact, horse, elephant, and mastodon dying out 

 about the same time in such different quarters. Will 

 Mr. Lyell say that some [same ?] circumstance killed 

 it over a tract from Spain to South America ? 



