186 THE SCIENCE OF BIOLOGY 



thousand years. Modern experimenters, like Darwin, 

 Mendel, and Morgan, have thrown much light upon the 

 workings of variation and heredity. The present situation 

 justifies the statement that since the publication of the 

 " Origin of Species" organic evolution has been substantiated 

 by evidence that is now overwhelming. 



The effect upon biological science of the acceptance of 

 Darwin's conclusions was startling. Both evolution and 

 natural selection were accepted forthwith. The biologist 

 sought to interpret old facts in a new way and to discover 

 new facts which confirmed the evolutionary hypothesis. 

 In zoology, the study of embryology, as a means of deter- 

 mining racial descent, was eagerly pursued, although it 

 eventually proved disappointing as an answer to the broader 

 problems of relationship. However, evolution was more 

 firmly established by means of this work. On the other hand 

 the investigations of recent years have assigned less im- 

 portance to the theory of selection. When it is understood 

 that Darwinism may be used to mean either organic evolu- 

 tion or its alleged cause, natural selection, or both evolution 

 and selection, it becomes apparent that the dispute over the 

 efficacy of selection is not a challenging of the comprehensive 

 theory of organic evolution. 



The biological position of the evolutionary doctrine has 

 been established. Evolution is the clue to the history of 

 living things. But the doctrine is most important to man- 

 kind, through its influence upon human thinking outside 

 strictly biological lines. Like the Copernican system of 

 astronomy, it has made the universe anew within the minds 

 of men. The concept of organic evolution has changed 

 man's concept of his position in the order of nature. It is 

 also changing our ideas regarding the organization of society. 

 Lines of thought, seemingly remote from the biological field 

 have been revolutionized. The end of this change has not 

 come to pass. 



