336 SCIENTIFIC THOUGHT. 



35. terms " natural selection " and " sexual selection " ap- 



" Natural f 



selection" peared for the first time in Darwin's writings. The 



and "sexual * 



selection." struggle for existence," and the resulting " survival of 

 the fittest " individuals, represent definite processes always 

 going on consciously or unconsciously in nature and in 

 human society ; nor is it less significant that many other 

 phrases have been coined, by which the same idea has been 

 made useful in other domains of research. " Hybrids," 

 " mongrels," " rudimentary organs," and " monstrous " 

 developments, which in earlier times were subjects of 

 mere curiosity, have been raised to scientific importance 

 as indicative of the concealed and mysterious agencies 

 by which natural forms are altered or maintained, and 

 natural processes encouraged or checked. "Environ- 

 ment " and " adaptation " open out great vistas of in- 

 quiry, whilst nearly all those different lines of search 

 and of reasoning have latterly become centred in the 

 great problem of " heredity "- the central question of 

 biological science. In addition to these, the older 

 terms of the naturalists and anatomists have received 

 new interpretations. It has been shown by Darwin 

 himself how the vague endeavours of system-makers, 

 since Linnseus, after a " natural " as distinguished from 



36. a merely " artificial system of classification " of living 



Meaning of . 



natural beings, implied " something more than mere resem- 



classiflca- 



tion - blance, and that this something more is " propinquity 



of descent the only known cause of the similarity 

 of organic beings it being the bond, hidden by various 

 degrees of modification, which is partially revealed to 

 us by our classifications." l In the light afforded by 



1 ' Origin of Species,' 1st ed., p. 413. 



