40 ORGANIC EVOLUTION 



less importance than Darwin thought ; but we shall 

 see that very recent work done by the newest school 

 of biologists — the bioinetricians, followers of Darwin's 

 distinguished first cousin, Mr. Francis Galton — 

 affords evidence which goes to show that Darwin 

 by no means overestimated the importance of this 

 factor. 



Of all the individuals of any species, living at 

 any given date, some will leave many descendants 

 — more or less like unto themselves — others will 

 leave few, and others none. It is a question of the 

 first importance to determine the factors which 

 decide whether a given individual is to belong to 

 one group or another : for if these be persistent in 

 their operation, the type of the race must necessarily 

 change. Now we have already seen that as man, by 

 artificial selection, chooses certain types of domestic 

 animals and puts them into the first group, whilst 

 relegating others to the last, so " Nature," by the 

 analogous process of " natural selection," similarly 

 allocates the individuals of any generation to one 

 or another category. In the process of artificial 

 selection, man chooses certain characters — now one, 

 now another — which please him ; in the process of 

 natural selection, " Nature " chooses always one 

 character and one only, that pleases her: which 

 character is fitness. It is now, further, to be found 

 that the individuals themselves exert a selective 

 action, the character which they choose as their 

 criterion being sexual attractiveness. That and that 

 alone is the concern of the chooser of a mate ; * but 



1 " Marrying for money " is a pathological phenomenon which 

 does not concern us here. 



