INTRODUCTORY NOTE TO CHAPTER II IN PRESENT EDITION 



As this chapter sets forth the main features of a theory 

 identical with that discovered by Mr. Darwin many years 

 before but not then published, and as it has thus an historical 

 interest, a few words of personal statement may be permissible. 

 After writing the preceding paper the question of how changes 

 of species could have been brought about was rarely out of 

 my mind, but no satisfactory conclusion was reached till 

 February 1858. At that time I was suffering from a rather 

 severe attack of intermittent fever at Ternate in the Moluccas, 

 and one day while lying on my bed during the cold fit, 

 wrapped in blankets, though the thermometer was at 88 

 F., the problem again presented itself to me, and something 

 led me to think of the "positive checks" described by Malthus 

 in his "Essay on Population," a work I had read several 

 years before, and which had made a deep and permanent 

 impression on my mind. These checks war, disease, famine 

 and the like must, it occurred to me, act on animals as well 

 as on man. Then I thought of the enormously rapid multi- 

 plication of animals, causing these checks to be much more 

 effective in them than in the case of man ; and while ponder- 

 ing vaguely on this fact there suddenly flashed upon me the 

 idea of the survival of the fittest that the individuals removed 

 by these checks must be on the whole inferior to those that 

 survived. In the two hours that elapsed before my ague fit 

 was over I had thought out almost the whole of the theory, 

 and the same evening I sketched the draft of my paper, and 

 in the two succeeding evenings wrote it out in full, and sent 

 it by the next post to Mr. Darwin. Up to this time the only 

 letters I had received from him were those printed in the 

 second volume of his Life and Letters, (vol. ii. pp. 95 and 108), 



