ON THE GENETIC VIEW OF NATURE. 



331 



specially with the actual fact and the function of varia- n. 



"Varia- 

 tion in the domain of living beings. He pushed the tion -" 



problem of variation and variability into the foreground, 

 and discussed one of its main features viz., its possible 

 effect and results. Since his time the eye of every 

 botanist, every zoologist, and every embryologist has 

 been directed towards the variability, transition, and 

 genesis of forms, to their history rather than to their 

 portraiture, whereas before him it was mostly attracted 

 by their seeming fixity and recurrence. Variations have 

 been studied on the large and on the minute scale in 

 geological strata at home and abroad, and the vexed 

 question has been raised as to their causes and laws, 

 Darwin having been mainly occupied with their existence 

 and operation, the results which they brought about, the 

 gradual alterations of the forms of living things. On 

 this side he tells us that he found an important clue 

 through reading a book which had appeared at the very 

 end of the eighteenth century, Malthus's ' Essay on the 

 Principle of Population.' l 



arose as simple varieties, and that 

 the species of each genus were all 

 descended from a common ancestor ; 

 but none of them gave a clue as to 

 the law or the method by which 

 the change had been effected. This 

 was still ' the great mystery ' " (p. 

 6). " Darwin, by his discovery of 

 the law of natural selection and his 

 demonstration of the great principle 

 of the preservation of useful varia- 

 tions in the struggle for life, has 

 not only thrown a flood of light on 

 the process of development of the 

 whole organic world, but also estab- 

 lished a firm foundation for all 

 future study of nature " (p. 9). 

 1 This essay appeared first in 



1798, and in the enlarged and much 

 improved form in which it is now 

 known in 1803. Darwin seems to 

 have come upon it accidentally. In 

 his Autobiography (' Life,' vol. i. 

 p. 83) he writes : " In October 1 838 

 that is, fifteen mouths after I had 

 begun my systematic inquiry I 

 happened to read for amusement 

 ' Malthus on Population,' and being 

 well prepared to appreciate the 

 struggle for existence which every- 

 where goes on, from long-continued 

 observation of the habits of animals 

 and plants, it at once struck me 

 that under these circumstances 

 favourable variations would tend 

 to be preserved, and unfavourable 



