CHARLES ROBERT DARWIN. 371 



years very curious about is to ascertain whether 

 the young of our domestic breeds differ as much 

 from each other as do their parents, and I have no 

 faith in anything short of actual measurement and 

 the Eule of Three. ... I have got my fan-tails 

 and pouters in a grand cage and pigeon-house, and 

 they are a decided amusement to me, and delight 

 to H." 



Of this book, Darwin himself says : " I worked 

 on true Baconian principles, and without any the- 

 ory collected facts on a wholesale scale, more 

 especially with respect to domesticated productions, 

 by printed inquiries, by conversation with skilful 

 breeders and gardeners, and by extensive reading. 

 When I see the list of books of all kinds which I 

 read and abstracted, including whole series of Jour- 

 nals and Transactions, I am surprised at my in- 

 dustry. I soon perceived that selection was the 

 keystone of man's success in making useful races 

 of animals and plants. . . . 



" In October, 1838, that is, fifteen months after I 

 had begun my systematic inquiry, I happened to 

 read '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- 

 stances favorable variations would tend to be 

 preserved, and unfavorable ones to be destroyed. 

 The result of this would be th*e formation of new 

 species. . . . But at that time I overlooked one 



