56 THE EVOLUTIONARY THEORY 



slight, favourable variations; aided in an important 

 manner, that is, in relation to adaptive structures, 

 whether past or present, by the direct action of external 

 conditions, and by variations which seem to us in our 

 ignorance to arise spontaneously." ^ 



In this description, the phrase "natural selection" 

 is of leading importance, and to understand Darwin's 

 use of it is to understand the essence of Darwinism. 

 It was suggested by the phenomena of artificial selec- 

 tion, in which desirable variations in the animal and 

 vegetable world are perpetuated and improved by select- 

 ing for breeding and culture those animals and vege- 

 tables only that possess the variations which are 

 desired. Many choice varieties of stock and of edible 

 fruits and vegetables owe their existence to artificial 

 selection. Now Darwin was led to believe that what 

 man thus assists nature to achieve within a brief period 

 of time is accomplished more slowly, but in an anal- 

 ogous manner, by unassisted nature. He therefore 

 called the process ''natural selection." The word 

 "selection" imphes intelhgent choice, but Darwin 



1 Origin of Species (6th American ed.), Vol. II. p. 293. His gen- 

 eral argument is summarized in ch. xv. Expositions of Darwin's 

 theory can be found in A. R. Wallace's Darwinism; R. H. Lock's 

 Recent Progress, ch. iii; V. L. Kellogg's Darwinism To-day, pp. 

 12-17; A. Weismann's Evolution Theory, Lees, ii, iii; V. F. Storr's 

 Development, ch. iii; M. M. Metcalf, Outline of the Theory of Organic 

 Evolution, pp. 3-31. Life and Letters of Chas. Darwin, by his son, F. 

 Darwin, 3 vols., is most valuable. A short life is given by Thos. Huxley, 

 in Darwiniana, pp. 254-302. See also on Darwin's theory, Bald- 

 win, Die. of Philos., s. w. "Existence (Struggle for)"; "Selection"; 

 "Variation"; and Encyc. Brit., 9th ed., s. v. "Evolution." 



