146 MEANING OF THE SYSTEM. 



feeding very largely upon herbivorous animals. Then again, all are 

 struggling to multiply in great numbers. Each organism produces 

 far more descendants than can in general be preserved. With a 

 definite degree of fertility, a corresponding amount of destruction 

 must take place ; for in the absence of the latter the number of 

 individuals would so increase in geometrical progression that no 

 locality would suffice for the sustenance of their progeny. If, on 

 the contrary, the protection afforded by fertility, size, special organiza- 

 tion, colour, etc., were removed, the species would soon vanish from 

 the earth. Amongst the complex conditions and interactions of life, 

 even the most remotely connected organisms struggle with each other 

 for existence (e.g., the clover and the mice); but the most violent 

 strife is waged between individuals of the same species, which seek 

 the same food and are exposed to the same dangers. In this strife it 

 necessarily happens that those individuals which are placed in the 

 most favourable situation, through their special properties, have the 

 greatest chance of maintaining themselves and of multiplying, and, 

 in consequence, of reproducing the modifications useful to the species 

 and of preserving them in their descendants, or even sometimes of 

 increasing them. 



Just as in the breeding of domesticated animals, an artificial selec- 

 tion is made by man to perpetuate and increase advantageous 

 variations; so in the natural breeding of wild animals, in conse- 

 quence of the struggle for existence, a selection is made by nature 

 which leads to the preservation of modifications useful to the 

 species. 



Since, however, the struggle for existence in closely related forms 

 must be the more violent the more nearly they resemble one another, 

 the most divergent types will have the greatest chance of enduring 

 and of producing descendants. Hence a divergence of characters 

 and an extinction of intermediate forms is the necessary consequence. 

 Thus by the combination of useful properties and by the accumula- 

 tion of hereditary peculiarities, which were primitively of little im- 

 portance, varieties gradually arise which ever diverge more and 

 more ; and this is what Darwin sought to prove by happily chosen 

 examples. We can now comprehend why everything in the organism 

 is directed towards one end, which is to ensure existence in the 

 most perfect way. The great series of phenomena which could hitherto 

 only receive a teleological explanation are thus brought into causal 

 relation, and can be explained as the inevitable result of efficient 

 causes, and their natural connection is thus rendered intelligible. 



