562 EVOLUTION 



and today it is accepted not only by biologists, but by theologians 

 and all thinking men. His book. Origin of Species, setting forth 

 his arguments for evolution in an irresistable way, was published 

 in 1859 and so great has been its influence that it is regarded as 

 one of the great books. This book was based upon many years 

 of investigation in which he visited many parts of the world and 

 made thousands of observations. The great force of his argument 

 is in his explanation of how new species are produced. Of 



Fig. 484. — Charles Darwin, the scientist who did most to establish the 

 theory of Evolution. 



(Taken by permission from "Recent Progreaa in the Study of Variation, Hereditary, and 

 ETOlution," by R. H. Lock, published by E. P. Button & Co.) 



course, Charles Darwin was by no means the first to offer an 

 explanation of evolution, but his explanation was so convincing 

 as to make it easy to believe the theory of evolution. He was 

 convinced that species are formed by the process of natural 

 selection. His idea was that organisms vary in all directions 

 and from the variants nature selects certain ones which eventually 

 become established as new species. In the following discussion 

 of the explanations of evolution, Darwin's ideas will be given 



