100 HEREDITY AND EVOLUTION IN PLANTS 



for evolution to produce the organic world as we now behold 

 it is longer than the age of the earth as understood from 

 geological and astronomical evidence. 



There is not space here to summarize the answers to all 

 these objections. Suffice it to say that scientific investi- 

 gation since Darwin's time has given us reasonably satis- 

 factory answers to most of them, so that now practically 

 no scientific man doubts the essential truth of evolution; 

 it is the corner stone of all recent science, the foundation 

 of all modern thought. 



80. The Modern Problem. But Darwinism left us 

 with a very large and very fundamental problem unsolved. 

 Upon what materials does natural selection act in the 

 formation of species? Obviously the "fittest" survives, 

 but what is the origin of the fittest? This problem Darwin- 

 ism did not solve. The solution of it is one of the most 

 fundamental and important tasks now being undertaken 

 by biologists. The most effective attack is by the method 

 of experimental evolution, which forms the subject of the 

 next chapter. 



