CHAPTER V 



HEREDITY AND EVOLUTION 



THE persistence of species is matter of common obser 

 vation. Hence the novelty of the thesis which Darwin 

 announced, and the difficulty of giving credence to 

 his theory, as if variation were quite as much a feature 

 in Nature as persistence. When, however, Darwin 

 stated his contention in these terms, that species are 

 not immutable, it became apparent that denial of 

 the persistence of species was not involved. Darwin 

 viewed organic life on a large scale, contemplating 

 the affinities which connect together whole groups of 

 organisms. He said, I had never deliberately applied 

 these views to a species taken singly ; l and he made 

 it his chief matter of congratulation that he had 

 shaken the belief in the separate creation of species. 



Laws of inheritance are conspicuous in the order of 

 Nature. These laws are closely related with variation, 

 as Spencer has shown. 2 In order that there may be 

 true progress, acquisition must become a permanent 

 possession. Without a law of inheritance, structural 

 gain would have been restricted to the individual. 

 Every life would have been doomed to struggle, as if 

 nothing had been achieved by progenitors. Depend 

 ence on ancestors implies gain to offspring from 



1 Descent of Man, p. 2. 



2 Herbert Spencer s Principles of Biology, i. p. 256. 



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