limits of zoology. But unless a sharp line is to be drawn 

 between the slow origin by evolution of the human species 

 and the later history of this species, the comparative and 

 genetic methods of analysis which render the earlier pro- 

 cess intelligible can scarcely fail to be of service in dealing 

 with the latter. The great danger, which the zoologist 

 himself clearly sees, arises from a tendency to ignore the 

 detail in formulating the general, to oversimplify the 

 problems of the more recent history. For human con- 

 scious elements are so complex and plastic that the prob- 

 lems of racial evolution are rendered far more intricate 

 than the broad zoological analysis of the origin of man as a 

 species. 



Psychology, in the second place, is a subject that is re- 

 lated to zoology by the closest of ties, the bond of union 

 being again the common human element. To be sure the 

 zoologist finds enough in his own field to occupy him fully, 

 but the comparative study of nervous systems, and of the 

 reflex, instinctive, intelligent, and reasoned responses of 

 animals brings him inevitably to consider the relation of 

 human mentality and consciousness to the other terms of 

 the animal series. Dealing strictly as a zoologist with 

 animals and their lives, the investigator learns that the 

 machine-like regularity of reflex and instinctive activities 

 is correlated, broadly speaking, with simple nervous or- 

 ganization ; that the plasticity of intelligent response is not 

 gained until the physical basis becomes far more compli- 

 cated; and finally that reason and consciousness are in 

 some way bound up with the higher development of the 

 nerve-centers or ganglia that make up the brain. So the 

 zoologist is inclined to believe that the comparative series 

 of mental grades which culminates in the consciousness, 

 or rather the self -consciousness of the adult human organ- 

 ism, and the series of developmental stages through which 

 the human mental structure passes during infancy and 



31 



