DARWIN 333 



with armour like that on the existing armadillos; 

 secondly, by the manner in which closely allied ani- 

 mals replaced one another in proceeding southwards 

 over the Continent ; and thirdly, by the South Ameri- 

 can character of most of the productions of the Gala- 

 pagos archipelago, and more especially by the man- 

 ner in which they differ slightly on each island of the 

 group, none of the islands appearing to be very an- 

 cient in a geological sense. It was evident that such 

 facts as these, as well as many others, could only be 

 explained on the supposition that species gradually 

 become modified ; and the subject haunted me. But it 

 was equally evident that neither the action of the 

 surrounding conditions,^ nor the will of the organ- 

 isms^ (especially in the case of plants) could account 

 for the innumerable cases in which organisms of 

 every kind are beautifully adapted to their habits 

 of life — for instance, a woodpecker or a tree frog 

 to climb trees, or a seed for dispersal by hooks or 

 plumes. I had always been much struck by such adap- 

 tations, and until these could be explained it seemed 

 to me almost useless to endeavour to prove by indirect 

 evidence that species have been modified. 



It was after his return in 1837 that Darwin 

 opened his first note-book for the collection of 

 facts which bore in any way on variation in ani- 

 mals and plants under domestication and in Na- 

 ture. He says: *'I worked on true Baconian prin- 

 ciples, and without any theory collected facts on 

 a wholesale scale, more especially with respect to 



iRe here refers to Buffon's factor. 



2He here refers to and misconceives Lamarck's factor. 



