18 FOOT-NOTES TO EVOLUTION, 
inheritance from their common ancestry. The differ- 
ences have come about through various natural influ- 
ences, chief among which is the competition in the 
struggle for existence between individuals and between 
species, whereby those best adapted to their surroundings 
live and reproduce their kind. Any advantage of the 
individual, no matter how small, must be a help in its life 
struggle. This advantage inherited becomes the gain of 
thespecies. The various influences connected with this 
struggle were summed up in the comprehensive term of 
“natural selection,” or, as Mr. Herbert Spencer has 
termed it, “the survival of the fittest.” The latter term 
is, however, only half as large as the former, because “ the 
survival of the existing” is in many regards a factor as 
potent as the actual survival of the fittest. To be onthe 
ground is a factor not less important in determining sur- 
vival than to have a special fitness for the conditions of 
life. The epithet “natural” in natural selection is also 
of vital importance as distinguished on the one hand from 
“ artificial,” or produced by human agency, and on the 
other hand from “supernatural,” or produced by un- 
knowable agencies. “Fitness” in this sense of course 
means simply the power to win in the particular kind of 
contest that may be in question, no moral element and 
no element of general progress being necessarily in- 
volved. The term “natural selection” originated from 
the use of the word “selection” by breeders of animals 
to indicate the process of “ weeding out” by which they 
improve their herds. For the method by which in 
Nature a new species is brought into existence seems 
to be precisely parallel to that by which we may arti- 
ficially produce a new breed of cows or of dogs, a new 
race of pigeons, or a new variety of roses. The record of 
man’s work in the creation of species covers some of the 
most glorious of human achievements, none the less won- 
