42 AUTOBIOGRAPHY. [ch. ii. 



mals covered with armour like that on the existing arma- 

 dillos ; secondly, by the manner in which closely allied ani- 

 mals replace one another in proceeding southwards over the 

 Continent; and thirdly, by the South American character 

 of most of the productions of the Galapagos archipelago, 

 and more especially by the manner in which they differ 

 slightly on each island of the group ; none of the islands 

 appearing to be very ancient 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 organisms 

 (especially in the case of plants) could account for the in- 

 numerable cases in which organisms of every kind are beau- 

 tifully adapted to their habits of life for instance, a wood- 

 pecker or a tree-frog to climb trees, or a seed for dispersal 

 by hooks or plumes. I had always been much struck by 

 such adaptations, and until these could be explained it 

 seemed to me almost useless to endeavour to prove by indi- 

 rect evidence that species have been modified. 



After my return to England it appeared to me that by 

 following the example of Lyell in Geology, and by collect- 

 ing all facts which bore in any way on the variation of ani- 

 mals and plants under domestication and nature, some light 

 might perhaps be thrown on the whole subject. My first 

 note-book was opened in July 1837. I worked on true Ba- 

 conian principles, and without any theory collected facts on 

 a wholesale scale, more especially with respect to domesti- 

 cated productions, by printed enquiries, by conversation 

 with skilful breeders and gardeners, and by extensive read- 

 ing. When I see the list of books of all kinds which I read 

 and abstracted, including whole series of Journals and 

 Transactions, I am surprised at my industry. I soon per- 

 ceived that selection was the keystone of man's success in 

 making useful races of animals and plants. But how se- 

 lection could be applied to organisms living in a state of 

 nature remained for some time a mystery to me. 



In October 1838, that is, fifteen months after I had be- 

 gun my systematic enquiry, I happened to read for amuse- 

 ment Malthus on Population, and being well prepared to 

 appreciate the struggle for existence which everywhere goes 

 on from long-continued observation of the habits of animals 

 and plants, it at once struck me that under these circum- 



