180 THE SCIENCE OF BIOLOGY 



for life." If one species could be shown to give rise to an- 

 other, the same process could be continued. No limit could 

 be set. And the types thus produced could depart indefi- 

 nitely from the parent form. Once the mutability of species 

 is admitted, the only reasonable conclusion is that evolution 

 has taken place. This argument was supported by an im- 

 mense collection of facts along observational and experi- 

 mental lines. The total result was overwhelming, coming as 

 it did more than one hundred years after the original pro- 

 mulgation of the theory of transmutation which had been 

 repeatedly rejected by the main body of naturalists. Evo- 

 lution was accepted so quickly by scientists that the world 

 was startled. This sudden conversion gave rise to the im- 

 pression, even among scientific workers, that no serious 

 contribution to evolutionary theory had been made before 

 the period of Darwin. 



Moreover, Darwin's second accomplishment, Natural Se- 

 lection, was accepted by science as a causo-mechanical ex- 

 planation of evolutionary change. The cogent statement and 

 the simplicity of the principle of selection were of great im- 

 portance for its acceptance along with the broader theory of 

 evolution. For a time, it seemed that selection offered a 

 complete explanation of evolutionary causation. Extended 

 exposition of the selection process will not be attempted, 

 because we are concerned with the general import of the 

 theory in biological and other lines of thought. 23 The tabu- 

 lation, known as Wallace's Chart, which is an admirable 

 brief exposition of natural selection, may be cited in this 

 connection. 



23 Brief statements of the theory of natural selection will be found in many 

 biological texts. But Darwin's own exposition, in the first chapters of the 

 "Origin of Species," is not so extended but that one can consult the original 

 source. G. J. Romanes, "Darwin and After Darwin," Vol. I, "The Darwinian 

 Theory" (1896), represents a post-Darwinian point of view. V. L. Kellogg, 

 "Darwinism Today," (1907) is a critical examination of the status of the 

 Darwinian theories at the end of half a century. 



