298 COOK 



In pre-evolutionary days there was no need to make special 

 studies of variation, since it was freely admitted by the scientific 

 public that the differences of varieties and even of species arose 

 from environmental influences upon normally stationary types. 

 The supposition was that genera had been created, rather than 

 species, though Linnaeus interfered with this view by combining 

 many of the groups recognized by his predecessors as genera 

 and by holding then that species also were specially created. 



The significance of this history is that the two ideas, first, that 

 of normally uniform and stationary species, and second, that of 

 the environmental causation of variations, were inherited from 

 the pre-evolutionary period and have continued to be used with- 

 out scientifically critical warrant. 



Moreover, the first quest for evolutionary causes was not made 

 in the direction of more thorough study of the constitution of 

 species, but was concerned rather with the exploration of the 

 boundaries and the gaps between species. The issue raised by 

 Darwin, and more especially by Huxley and other controversial 

 biologists, was that of proving to the theological public that new 

 species could be produced by evolution, instead of definitely 

 investigating the means by which the evolutionary progress of 

 species is accomplished. The chief interest was directed, not 

 to evolution itself, but to the two results of evolution, speciation 

 and adaptation, the generally admitted pre-Darwinian doctrine 

 of environmental causation of variations serving all the imme- 

 diate needs of the discussion. 



TYPES OF EVOLUTIONARY THEORIES. 



Static Theories. — According to the theory to which the 

 name Darwinism is generally, though unjustly, limited, evolu- 

 tion is brought about by the influence of environment, which 

 causes organisms to vary, preserves advantageous modifications, 

 diminishes or eliminates the relatively unfit, and thus transforms 

 or subdivides species. 1 Such theories may be called static be- 

 cause they assume that species are normally in a state of rest or 



1 "Darwin has left the causes of variation and the question whether it is lim- 

 ited or directed by external conditions perfectly open." Huxley, Life and 

 Letters, 2 : 205, 1901. 



