46 CHARLES DARWIN. 



n 



causes of evolution which were suggested to him by 

 the facts of nature, and that some general idea of 

 natural selection presented itself to him at times, 

 although without any of the force and importance 

 it assumed in his mind at a later time. 



In October, 1838, he read " Mai thus on Popula- 

 tion," and as he says : — 



"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 circumstances favourable variations 

 would tend to be preserved, and unfavourable ones to be 

 destroyed. The result of this would be the formation of new 

 species. Here then I had a theory by which to work." 



In June, 1842, he wrote a brief account of the theory, 

 occupying thirty-five pages. In Lyell's and Hooker's 

 introduction to the joint paper by Darwin and 

 Wallace in the Linnean Society's Journal (1858) it 

 is stated that the first sketch was made in 1839, but 

 Francis Darwin shows {" Life and Letters," 1887, 

 Vol. II. pp. 11, 12) that in all probability this is an 

 error — a note of Darwin's referring to the first com- 

 plete grasp of the theory after reading Malthus, being 

 mistaken for a reference to the first written account. 



In 1844 the sketch was enlarged to a written 

 essay occupying 231 pages folio — "a surprisingly 

 complete presentation of the argument afterwards 

 familiar to us in the ' Origin of Species ' " published 

 fifteen years later. Professor Huxley, after reading 

 this essay, observed that " much more weight is a| 

 attached to the influence of external conditions in 



