292 COOK 



expense of vitality, and at the ultimate cost of extinction, where- 

 ever such experiments are continued for a sufficient period of 

 time. 



More recently still, a son of Charles Darwin, speaking as 

 President of the British Association for the Advancement of 

 Science, has reflected the conclusion which the scientific world 

 has drawn from his father's doctrine of natural selection, that it 

 is the cause of evolution. 



" The fundamental idea in the theory of natural selection is 

 the persistence of those types of life which are adapted to their 

 surrounding conditions, and the elimination by extermination 

 of the ill-adapted types. The struggle for life amongst forms 

 possessing various degrees of adaptation to slowly varying con- 

 ditions is held to explain the transmutation of species." 1 



It may be doubted whether Charles Darwin himself would 

 ever have ventured upon so direct and so generalized a state- 

 ment. He was anxious always that his readers should take a 

 favorable view of the feasibility of evolution through natural 

 selection, but at the same time he could not forget the immense 

 improbability of the claim that all characters are adaptive and 

 useful. This caution was not shared by Wallace, who has 

 never hesitated to proclaim selection as the cause of evolution, 

 alike efficient and sufficient. With Darwin, natural selection 

 remained a theory, and he never ceased to seek additional evi- 

 dence to support or supplement it, but with Wallace and many 

 others it soon became an undoubted fact, or at least an unques- 

 tioned formula. 



" Suffice it to say here that this theory of natural selection — 

 meaning the elimination of the least fit and therefore the ulti- 

 mate 'survival of the fittest' — has furnished a rational and 

 precise explanation of the means of adaptation of all existing 

 organisms to their conditions, and therefore of their transforma- 

 tion from the series of distinct but allied species which occupied 

 the earth at some preceding epoch. In this sense it has actually 

 demonstrated the ' origin of species,' and, by carrying back this 

 process step by step into earlier and earlier geological times, we 



1 Darwin, G. 11., 1905. Address of President of the British Association for the 

 Advancement of Science; Nature, 72 : 370. Science, N. S., 22 : 258. 



