I.] Darwinism Verified. 15 



selection, like a power that slumbers not nor sleeps, 

 is ever preserving the stability of species by seizing 

 all individual peculiarities that oscillate within narrow 

 limits on either side of the mean that is most advan- 

 tageous to the species, while cutting off all such pecu- 

 liarities as transgress these limits. Domesticated 

 animals, protected from the exigencies of wild life, 

 often exhibit great varieties in colouring, while wild 

 animals of the same genus or species are monotonously 

 coloured, because only one kind of colouring will aid 

 them in catching prey or eluding enemies, and all the 

 variations are killed out. Who can doubt that ante- 

 lopes are so fleet, only because all but the fleetest 

 individuals are sure to be overtaken and eaten by 

 lions } Protected from the lions, a thousand genera- 

 tions might well make them as lazy and clumsy as 

 sheep. 



Operating in this stern way, natural selection secures 

 the general adaptation of each race of organisms to 

 the conditions of Hfe which surround it. And so long 

 as a species continues surrounded by circumstances 

 that are tolerably persistent, natural selection main- 

 tains its stability of character. Thus what the older 

 naturalists called the " fixity of species " is fully 

 accounted for. But a " fixity of species " that is 

 maintained only under such conditions is really no 



