206 Instinct and Intelligence 



belief that all animals and plants have 

 descended from some one prototype. He 

 states that in consequence of the struggle for 

 existence any variation however slight, and from 

 whatever cause it proceeds, if it be in any 

 degree profitable to an individual of any species 

 in its complex relation to its environment, 

 it will tend to protect that individual, and 

 generally will be inherited by its offspring. 

 Darwin calls the principle by which each 

 slight useful variation of an organism is 

 preserved the principle of natural selection, in 

 order to emphasise its relation to man's power 

 of selective breeding. For it is well known 

 that by careful selection of the stock we can 

 adapt organic beings to our own use through 

 the accumulation of slight but useful variations. 

 Natural selection, however, is a power con- 

 stantly ready for action, and is as immeasurably 

 superior to man's efforts as the work of nature 

 is to that of art. 1 



Darwin repeatedly insists on the fact, that 

 natural selection could not be effective unless 



1 The Origin of Species by Means of Natural Selection, by 

 Charles Darwin, M.A., 1859, p. 63. 



