22O UNIVERSITY OF MISSOURI BULLETIN 



of investigation for a long period following, so speculations 

 concerning ancestral relationships dominated zoology from 

 Darwin's time to within recent years. Science does not de- 

 velop logically, but follows the paths of least resistance, and, 

 with the almost endless wealth of material at hand, it is not 

 surprising that so facinating a study should have absorbed 

 the interest of zoologists. The direction which the investiga- 

 tion took, however, had a very unfortunate consequence, for 

 it led men away from the real and fundamental problems of 

 evolution. Not only had the experimental study of varia- 

 tion and heredity made some progress before D'arwin, but he 

 himself had clearly shown that evolution is but a process of 

 variation and heredity, and by his own laborious collecting 

 of facts had, in his book on "The Variation of Animals and 

 Plants under Domestication," laid the foundation of the science 

 of genetics. Blind to the greater significance of this phase 

 of his work, his followers plunged into the field of evolutionary 

 speculation, led on by the will-o'-the-wisp of phylogeny, and 

 within a very few years after the publication of "The Origin" 

 the field of experimental breeding had been practically aban- 

 doned. It was not until the close of the century that its cul- 

 tivation was seriously resumed. 



Summary. The fact of organic evolution had at last 

 passed from the realm of speculation, for with the establish- 

 ment of Darwin's views the reality of descent was no longer 

 left in doubt. As to the method of the process, or the means 

 by which it has been brought about, Darwin had proposed his 

 theory of natural selection, which, with the triumph of the 

 evolutionary idea, was carried along as a rider and met with 

 the same general acceptance. 



Since post-Darwinian problems are concerned chiefly with 

 the method of evolution, let us turn our attention to a consid- 

 eration of this phase of the subject. 



