( Ixviii ) 



prime factor, or even as a factor of any value, in specific 

 modification ; it is perfectly logical to hold the mind in a state 

 of suspension, and to declare that the theory is inadequate, 

 but it is not given to many minds to rest content with a pure 

 negation. It will mark a decadent period in the history of 

 science when destructive criticism alone prevails. For my 

 own part, I long ago came to the conclusion that the funda- 

 mental principles were established with sufficient firmness to 

 warrant the deductive use of the theory in the same way that 

 we use working hypotheses in other departments of science, 

 and the result has not been disappointing.* 



The essence of the theory of natural selection is contained 

 in the phrase " utility of specific characters." The sub- 

 title of the " Origin of Species," published in 1859 and 

 retained in all subsequent editions, is " The Preservation of 

 favoured Eaces in the Struggle for Life." The races are 

 "favoured" because they have acquired, by the action of 

 selection upon favourable variations, some character or 

 characters which give them a more or less permanent 

 footing in the economy of nature. The distinction, if any 

 exists, between a race and a species is, as systematists well 

 know, often quite arbitrary and frequently, if not invariably, 

 resolves itself into a question of individual judgment. The 

 criterion which the producer of artificial races employs as an 

 ai'gument in favour of community of descent from a common 

 stock, viz., fertility, inter sc, finds no place in the specific 

 diagnoses of the systematists. The question whether this 

 distinction is an absolute one remains as a subject for experi- 

 mental investigation in much about the same condition as it 

 was left by Darwin. It is surprising that this point, which, 

 as I may remind you, is the one flaw of which the existence 

 was frequently pointed out by Prof. Huxley, has not been 

 taken up as a matter of serious inquiry by biologists. The 

 want of an experimental station, to which allusion was made 

 in my address of last year, is no doubt responsible for the 



* See some remarks by Prof. Poulton in this sense {op. cit., p. 143). Even 

 Mr. Bateson, whom nobody will accuse of any bias in favour of Darwin's 

 views, admits that " Natiiral selection . . . is obviously a ' true cause ' 

 at the least " (" Materials for the Study of Variation," p. 5). 



