610 APPENDIX B. 



there is no sucli 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 adap tation for all 

 purposes. It implies the process which Nature can alone carry 

 on — the leaving alive of those which are best able to utilize sur- 

 rounding aids to life, and best able to combat or avoid surround- 

 ing dangers. And while this phrase covers the great mass of 

 cases in which there are preserved 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 increase any serviceable trait, only if that trait 

 conduces to prosperity of the individual, or of posterity, or of 

 both, in an important degree. There can be no increase of any 

 structure by natural selection unless, amid all the slightly vary- 

 ing structures constituting the organism, increase of this particu- 

 lar one is so advantageous as to cause greater multiplication of 

 the family in which it arises than of other families. Variations 

 which, though advantageous, 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 

 individual having it in an unusual degree is more likely than 

 others to survive ; and, among descendants, to leave some simi- 

 larly endowed or more endowed, who again transmit the variation 

 with, in some cases, increase. Clearly this highly useful power 

 may be developed by natural selection. So also, for like reasons, 

 may quickness of vision and delicacy of hearing ; though it may 

 be remarked in passing that since this extra sense-endowment, 

 serving to give early alarm, profits the herd as a whole, which 

 takes the alarm from one individual, selection of it is not so easy, 

 unless^ it occursjii_acon quering s tag. But now suppose that one 

 member of the herd — perhaps because of more efficient teeth, 

 perhaps by greater muscularity of stomach, perhaps by secretion 

 of more appropriate gastric juices — is enabled to eat and digest a 

 not uncommon plant which the others refuse. This peculiarity 

 may, if food is scarce, conduce to better self-maintenance, and 

 better fostering of young if the individual is a hind. But unless 

 this plant is abundant, and the advantage consequently great, 

 the advantages which other members of the herd gain from other 



