278 TJie Unity of the Organism 



smaller ones being for the most part subdivisions under the 

 larger. Then let us imagine this system of behavior-knowl- 

 edge compared exhaustively with a later-acquired, equally 

 exhaustive knowledge of the corporeal nature of all animals. 

 The two systems would be found to match each other very 

 nearly as closely as though the two had been worked out to- 

 gether, much as they are being actually elaborated by struc- 

 tural and functional zoology. In other words, the species, 

 genera, orders, and so on, of animals are differentiated from 

 one another and coordinated with one another by their "be- 

 havior," that is, by their whole round of psychical and reflex 

 attributes, much as they are by their corporeal attributes. 



The inductive evidence for such a generalization is being 

 produced at the present time by three quite definitely marked- 

 off kinds of research. These may be designated as ( 1 ) quali- 

 tative field researches, (2) laboratory experimental re- 

 searches, and (3) quantitative field researches, the definitely 

 quantitative method being statistical. 



The first-mentioned class of investigations is typified by 

 the earlier field zoologists, whose aim was to learn, as ex- 

 haustively as possible in a purely qualitative way, the habits 

 of animals in nature. Workers of this class are the typical 

 zoological naturalists of the history of animal biology. 

 Aristotle, Conrad Gesner, John Ray, Charles Linne, P. S. 

 Pallas, Gilbert White, J. J. Audubon, J. H. Fabre, A. R. 

 Wallace and A. Forel may be named as conspicuous examples 

 of pre-modern members of this class ; and Charles Darwin 

 stands out sharply as a representative of it, but as a transi- 

 tion to the modern period, the transitional character of 

 Darwin being seen not only in the doctrines he proposed but 

 as well in his intimate combination of the experimental 

 method with the older method of observation. 



By the modern period of research in field zoology I mean 

 the period during which, while the natural history point of 

 view and attitude are retained, the critical rigor of modern 



