806 THE POPULAR SCIENCE MONTHLY. 



processes are analogous and operate in the same way. Now this 

 is untrue. They are analogous only within certain narrow limits ; 

 and, in the great majority of cases, natural selection is utterly in- 

 capable of doing that which artificial selection does. 



To see this it needs only to de-personalize Nature, and to re- 

 member that, as Mr. Darwin says, Nature is " only the aggregate 

 action and product of many natural laws [forces]." Observe its 

 relative shortcomings. Artificial selection can pick out a particu- 

 lar trait, and, regardless of other traits of the individuals display- 

 ing it, can increase it by selective breeding in successive genera- 

 tions. For, to the breeder or fancier, it matters little whether 

 such individuals are otherwise well constituted. They may be in 

 this or that way so unfit for carrying on the struggle for life, that, 

 were they without human care, they would disappear forthwith. 

 On the other hand, if we regard Nature as that which it is, an as- 

 semblage of various forces, inorganic and organic, some favorable 

 to the maintenance of life and many at variance with its mainte- 

 nance — forces which operate blindly — we see that there is no such 

 selection of this or that trait, but that there is a selection only of 

 individuals which are, by the aggregate of their traits, best fitted 

 for living. And here I may note an advantage possessed by the 

 expression " survival of the fittest " ; since this does not tend to 

 raise the thought of any one character which, more than others, 

 is to be maintained or increased ; but tends rather to raise the 

 thought of a general adaptation for all purposes. It implies the 

 process which Nature can alone carry on — the leaving alive of 

 those which are best able to utilize surrounding aids to life, and 

 best able to combat or avoid surrounding dangers. And while 

 this phrase covers the great mass of cases in which there are pre- 

 served well-constituted individuals, it also covers those special 

 cases which are suggested by the phrase " natural selection," in 

 which individuals succeed beyond others in the struggle for life 

 by the help of particular characters which conduce in important 

 ways to prosperity and multiplication. For now observe the fact 

 which here chiefly concerns us, that survival of the fittest can in- 

 crease any serviceable trait only if that trait conduces to prosper- 

 ity of the individual, or of posterity, or of both, in an important 

 degree. There can be no increase of any structure by natural se- 

 lection unless, amid all the slightly varying structures constitut- 

 ing the organism, increase of this particular one is so advanta- 

 geous as to cause greater multiplication of the family in which 

 it arises than of other families. Variations which, though ad- 

 vantageous, fail to do this, must disappear again. Let us take 

 a case. 



Keenness of scent in a deer, by giving early notice of approach- 

 ing enemies, subserves life so greatly that, other things equal, an 



