132 THE DOCTRINE OF DESCENT. 



opponents of the great inquirer endeavour to suppress 

 his merits and authority by maintaining that he is pro- 

 perly a mere dilettante, dealing with general abstrac- 

 tions, '"** a stranger to the keen observation which takes 

 full account of facts. How Darwin arrived at the idea 

 which has made an epoch in science, he has himself 

 made known in the introduction to his first work on 

 the doctrine of Descent, namely, the " Origin of 

 Species;""''^ and in more detail in a letter to Haeckel, 

 published by the latter in his " History of Creation" 

 (Naturlichen Schopfungsgeschichte). 



" Having reflected much on the foregoing facts, it 

 seemed to me probable that allied species were de- 

 scended from a common ancestor. But during several 

 years I could not conceive how each form could have 

 been modified so as to become admirably adapted to 

 its place in nature. I began, therefore, to study do- 

 mesticated animals and cultivated plants, and after 

 a time perceived that man's power of selecting and 

 breeding from certain individuals was the most power- 

 ful of all means in the production of new races. Having 

 attended to the habits of animals and their relations to 

 the surrounding conditions, I was able to realize the 

 severe struggle for existence to which all organisms are 

 subjected ; and my geological observations had allowed 

 me to appreciate to a certain extent the duration of 

 past geological periods. With my mind thus prepared 

 I fortunately happened to read Malthus's " Essay on 

 Population;" and the idea of natural selection through 

 the strui^crle for existence at once occurred to me. Of 

 all the subordinate points in the theory, the last which 

 1 understood was the cause of the tendency in the 



