252 LIFE OF DARWIN 



become modified ; and the subject haunted me.' His 

 first note-book for the accumulation of facts bearing on 

 the question was opened in July 1837, and from that 

 date he continued to gather them l on a wholesale 

 scale, more especially with respect to domesticated 

 productions, by printed inquiries, by conversation with 

 skilful breeders and gardeners, and by extensive read- 

 ing.' He soon perceived that selection was the secret 

 of success in the artificial production of the useful 

 varieties of plants and animals. But how this principle, 

 so fertile in results when employed by man, could be 

 applied in explanation of Nature's operations, remained 

 a mystery to him until in October 1838, when, hap- 

 pening to read for amusement Malthus' book On the 

 Principle of Population, he found at last a theory with 

 which to work. With this guiding principle he insti- 

 tuted a laborious investigation on the breeding of 

 pigeons, and experiments on the flotation of eggs, the 

 vitality of seeds, and other questions, the solution of 

 which seemed desirable as his researches advanced. 

 He says himself that, to avoid prejudice in favour of 

 his own views, he refrained for some time from writing 

 even the briefest sketch of the theory he had formed, 

 and that it was not until June, 1842, that he allowed 

 himself the satisfaction of writing a very brief pencil 

 abstract in thirty-five pages, which two years afterwards 

 he enlarged to 230 pages, and had fairly copied out. 

 This precious manuscript was the germ of the Origin 

 of Species. 



With characteristic caution, however, he kept his 

 essay in his desk, and with equally characteristic 

 ardour, industry and patience went on with the 



