ZOOLOGICAL SCIENCE 211 



after the middle of the century, the genetic relationship be- 

 tween animal and human behavior became an absorbing 

 problem. Darwin's book upon " The Expression of the Emo- 

 tions in Man and Animals" (1872) is representative of the 

 underlying assumption that human behavior is an outcome 

 of evolution from the behavior of higher vertebrates. The 

 results of the best of this investigation, by such men as 

 Lubbock, Romanes, Preyer, and others, have been largely 

 confirmed. It is important to note that their work was ex- 

 perimental as well as observational and that it must be 

 highly regarded when we consider that "these investigators 

 were interested in the origin and evolution of responses and 

 of psychic phenomena, and not in the mechanics of reac- 

 tions." u 



Toward the end of the nineteenth century interest again 

 swung in the direction of the reduction of animal behavior 

 to mechanical principles. This interpretation of behavior 

 has been widely advertised in recent decades and experi- 

 mental methods have been much in evidence. But observa- 

 tion is still of great importance. However much we may 

 desire to reduce a problem to one critical experiment, obser- 

 vation is frequently a necessary preliminary to the experi- 

 mental attack. At the present day, the sane verdict on the 

 question whether the animal body is a machine, whose be- 

 havior is predictable in terms of a mechanical system, is that 

 the case is not yet proven, although many simple responses 

 appear to be mechanistic in their nature. 25 



24 The paper by S. O. Mast on the "Problems, Methods and Results in 

 Behavior," Science, Dec. 13, 1918, from which the above quotation has been 

 drawn, contains an authoritative resume of the history and present standing 

 of the study of behavior. 



25 The volumes by J. Loeb, "The Mechanistic Conception of Life" (1912) 

 and J. S. Haldane, the "Organism and Environment" (1917) represent, on 

 the one hand, the point of view of an extreme mechanist, and on the other, 

 that of an investigator who is an anti-mechanist rather than a vitalist. Hans 

 Driesch, in "The Science and the Philosophy of the Organism" (1908), has 

 pushed the vitalistic theories to a greater extreme than any biologist of the 

 present generation, using the facts observed in development as the principal 



