2 24 READINGS IN EVOLUTION, GENETICS, AND EUGENICS 



of life, and variability ensues; but similar changes of conditions might 

 and do occur under nature. Let it also be borne in mind how infinitely- 

 complex and close-fitting are the mutual relations of all organic beings 

 to each other and to their physical conditions of life; and consequently 

 what infinitely varied diversities of structure might be' of use to 

 each being under changing conditions of life. Can it, then, be 

 thought improbable, seeing that variations useful to man have 

 undoubtedly occurred, that other variations useful in some way to 

 each being in the great and complex battle of life, should occur in 

 the course of many successive generations ? If such do occur, can 

 we doubt (remembering that many more individuals are born than 

 can possibly survive) that individuals having any advantage, however 

 slight, over others, would have the best chance of surviving and of 

 procreating their kind ? On the other hand, we may feel sure that 

 any variation in the least degree injurious would be rigidly destroyed. 

 This preservation of favorable individual differences and variations, 

 and the destruction of those which are injurious, I have called 

 Natural Selection, or the Survival of the Fittest. Variations neither 

 useful nor injurious would not be affected by natural selection, and 

 would be left either a fluctuating element, as perhaps we see in certain 

 polymorphic species, or would ultimately become fixed, owing to the 

 nature of the organism and the nature of the conditions. 



Several writers have misapprehended or objected to the term 

 Natural Selection. Some have even imagined that natural selection 

 induces variability, whereas it implies only the preservation of such 

 variations as arise and are beneficial to the being under its conditions 

 of life. No one objects to agriculturists speaking of the potent effects 

 of man's selection; and in this case the individual differences given by 

 nature, which man for some object selects, must of necessity first 

 occur. Others have objected that the term selection implies conscious 

 choice in the animals which become modified; and it has even been 

 urged that, as plants have no volition, natural selection is not applic- 

 able to them! In the literal sense of the word, no doubt, natural 

 selection is a false term; but who ever objected to chemists speaking 

 of the elective affinities of the various elements ?— and yet an acid 

 cannot strictly be said to elect the base with which it in preference 

 combines. It has been said that I speak of natural selection as an 

 active power or Deity; but who objects to an author speaking of the 

 attraction of gravity as ruling the movements of the planets ? Every- 

 one knows what is meant and is implied by such metaphorical expres- 



