THE POPULAR SCIENCE MONTHLY
of racial evolution, they are still fellow-workers, for in the case of physical anthropology of human races at least the methods are the same which are employed in zoology generally. Of course it would be absurd for any one to contend that all the problems of anthropology are strictly zoological questions; to qualify here an investigator must be familiar with linguistics, racial customs and beliefs, and many subjects that are as such apparently outside the 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 process 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 conscious elements are so complex and plastic that the problems 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 related 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 thestudy 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 organization; that the plasticity of intelligent response is not gained until the physical basis becomes far more complicated; 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 organism, and the series of developmental stages through which the human mental structure passes during infancy and childhood, indicate an evolution in time of the psychic being of man. Whatever may be the outcome of further study, Romanes, Lloyd Morgan, Forel and Thorndike, among those of modern times, have demonstrated that the genetic methods of zoology are useful instruments for the psychologist, who, I believe, is becoming more and more a student of zoological materials as he realizes the advantage of studying the simpler psychic phenomena of animals lower than man.
In venturing to speak of the relation of zoology to sociology and ethics, I am well aware that I shall be charged with straying beyond