Survival of the Fittest. 437 
Seeing what a potent influence the principle of Selection 
has in the hands of man, in regard to variation, can it be 
applied in nature? We can see that it can act most effect- 
ually. But in our domestic productions the variability is 
not directly produced by man, for he can neither originate 
varieties nor prevent their occurrence. All he can do is to 
preserve and accumulate such as do occur. Unintentionally 
he exposes organic beings to new and changing conditions of 
life, for under domestication, plant and animal organizations 
become in some degree plastic, and variability ensues. Sim- 
ilar changes, however, do occur in nature. When it is borne 
in mind how infinitely complex and close-fitting are the mutual 
relations of all organic beings to each other, and to their 
environment, and consequently what infinitely-varied diver- 
sities of structure may be of advantage to each being under 
altered conditions, 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 sometimes occur in 
the course of tens of thousands of generations? If such do 
occur, can we doubt, when it is remembered that many more 
individuals are born than can possibly survive, that individ- 
uals possessing any advantage, no matter how slight, over 
their fellows would have the best chance of surviving and of 
procreating their kind? Any variation, on the other hand, 
we may feel sure if in the least degree injurious would be 
rigidly destroyed. This preservation of useful and favorable 
variations, and the destruction of those that are injurious, is 
called Natural Selection, or the Survival of the Fittest. 
Variations neither advantageous nor deleterious would not 
be affected by Natural Selection, and would be left either a 
fluctuating element, as seen in certain polymorphic species, 
or would alternately become fixed, owing to the nature both 
of the organism and its conditions. 
We shall best understand the probable cause of Natural 
Selection by taking a country undergoing some physical 
