CH. XVIII The Evolution of Evolution Theories 295 



satisfied ; he advanced to one of his own — to the theory of 

 natural selection, the characteristic feature of Darwinism. 



Let us state this theory, which was foreseen by Matthew, 

 Wells, Naudin, and others, was developed simultaneously 

 by Darwin and by Alfred Russel Wallace, and has attained 

 remarkable acceptance throughout the world. 



All plants and animals produce offspring which, though 

 like their parents, usually differ from them in possessing 

 some new features or variations. These are of more or 

 less obscure origin, and are often termed fortuitous or in- 

 definite. But throughout nature there is a struggle for 

 existence in which only a small percentage of the organisms 

 born survive to maturity or reproduction. Those which 

 survive do so because of the individual peculiarities which 

 have made them in some way more fit to survive than their 

 fellows. Moreover the favourable variation possessed by 

 the survivors is handed on as an inheritance to their off- 

 spring, and tends to be intensified when the new generation 

 is bred from parents both possessing the happily advan- 

 tageous character. This natural fostering of advantageous 

 variations and natural elimination of those less fit, explain 

 the general modification and adaptation of species, as well 

 as the general progress from simpler to higher forms of 

 life. 



This theory that favourable variations may be fostered 

 and accumulated by natural selection till useful adaptations 

 result is the chief characteristic of Darwinism. Of this 

 theory Prof. Ray Lankester says : " Darwin by his discovery 

 of the mechanical principle of organic evolution, namely, the 

 survival of the fittest in the struggle for existence, completed 

 the doctrine of evolution, and gave it that unity and au- 

 thority which was necessary in order that it should reform 

 the whole range of philosophy." And again he says : " The 

 history of zoology as a science is therefore the history of 

 the great biological doctrine of the evolution of living things 

 by the natural selection of varieties in the struggle for exist- 

 ence, — since that doctrine is the one medium whereby all 

 the phenomena of life, whether of form or function, are 

 rendered capable of explanation by the laws of physics and 



