'58 THE MEANING OF EVOLUTION 



life and no one could foretell accidents. Mr. Dar- 

 win made clear that it was not a question of chance. 

 That which might happen to any individual animal 

 might be what we, not knowing the process, called 

 accident, and yet there could be no possible doubt 

 that those who succeeded were better fitted to battle 

 with life than those who failed, and that their suc- 

 cess was due primarily to their being thus advantaged. 

 Consequently, if generation by generation the so-called 

 accidents of life are constantly eliminating the unfit 

 in overwhelming proportions, not only must the posi- 

 tively unfit disappear, but even the less fit. The more 

 keen the struggle, the fewer could survive and the 

 fitter they must be to survive at all. This is Selec- 

 tion. These, then, are Darwin's four great factors 

 of evolution : Heredity, Variation, Multiplication, Se- 

 lection. 



From these it results that the animals and plants 

 naturally become better adapted to the situation in 

 which they are placed. When, as is constantly hap- 

 pening through the history of the earth, a change oc- 

 curs in the physical geography of any region, when 

 a plain is lifted to be a plateau, or a mountain chain 

 is submerged until it becomes a row of small islands, 

 this alteration will produce uncommon hardships 

 among animals, even though they were well fitted to 

 the old conditions. Any animal or any species of 



