CHAP. xin. EVOLUTION AND NATURAL SELECTION. 139 



skill and logical power as to carry conviction to the 

 minds of all unprejudiced readers; but none of these 

 writers suggested any definite theory of how the change 

 of species actually occurred. That was first done in 

 1858; and in connection with it I may, perhaps, venture 

 to give a few personal details. 



Ever since I read the " Vestiges " I had been con- 

 vinced that development took place by means of the ordi- 

 nary process of reproduction ; but though this was widely 

 admitted, no one had set forth the various kinds of evi- 

 dence that rendered it almost a certainty. I endeavored 

 to do this in an article written at Sarawak in February, 

 1855, which was published in the following September 

 in the " Annals of Natural History." Relying mainly 

 on the well-known facts of geographical distribution and 

 geological succession, I deduced from them the law, or 

 generalization, that, " Every species has come into exist- 

 ence coincident both in Space and Time with a Pre- 

 existing closely allied Species " ; and I showed how many 

 peculiarities in the affinities, the succession, and the dis- 

 tribution of the forms of life, were explained by this 

 hypothesis, and that no important facts contradicted it. 



Even then, however, I had no conception of how or 

 why each new form had come into existence with all its 

 beautiful adaptations to its special mode of life; and 

 though the subject was continually being pondered over, 

 no light came to me till three years later (February, 

 1858), under somewhat peculiar circumstances. I was 

 then living at Ternate in the Moluccas, and was suffer- 

 ing from a rather severe attack of intermittent fever, 

 which prostrated me for several hours every day during 

 the cold and succeeding hot fits. During one of these 



