SEXUAL SELECTION 405 



In warning coloration or terrifying attitudes, nothing can be warned 

 or terrified which does not see the warning or terrifying individual. 

 The only question that arises is again whether the warned or terrified 

 one must be possessed of sufficient intelligence to think the matter over 

 and decide according to the evidence presented to it by the visual 

 mechanism or whether it merely obeys the first impulse. Wallace him- 

 self proposed this theory of warning coloration, and it must stand or 

 fall on purely theoretical grounds along with the theory of sexual 

 selection, postulating, as it does, the same mechanisms in the warned 

 individual that Darwin's hypothesis postulates in the attracted indi- 

 vidual. There is, however, more direct observational evidence in favor 

 of warning coloration than there is in favor of sexual selection. Birds, 

 as Wallace showed, are warned by certain colors of butterflies. 



Whitman's 4 observations on pigeons show that their responses and 

 reactions are in many cases purely instinctive, being elicited without 

 previous education or experience, and occur only when the group of 

 conditions is right. Instinct, to me, at least, means a definite response 

 to a definite group of afferent impulses. The afferent impulses once set 

 up, the response of the central nervous system is the same under the 

 same conditions. As Whitman expressed it, "organization shapes be- 

 havior," a statement directly in line with Hermann's law of specific 

 response to stimulation. And from this statement of Whitman's dates 

 the transition of the discussion of animal behavior in metaphysical 

 terms to its discussion in terms of biological entities. In animal 

 behavior, organization centers largely, though not wholly, 5 around the 

 central nervous system and its associated afferent and efferent channels 

 and sense organs. Internal secretions of various ductless glands of the 

 body, and afferent nervous impulses from certain of these various 

 glands are, of course, to be considered in animal behavior, and all of 

 them have their influence on the instinctive responses of animals at 

 various seasons of the year. Yet all these things are to be considered as 

 a part of the organization of the individual at any one time. And the 

 conviction is slowly growing, in my own mind, at least, that it is not so 

 much a single afferent impulse as it is groups of afferent impulses that 

 determine the reactions of animals. A few illustrations will make this 

 point clearer. 



Hunger has been shown to be associated with definitive movements 

 of the stomach in man, and hence with definitive afferent impulses from 

 the stomach. 50 In the wider sense of the term, hunger is of reflex origin. 

 The feeding reactions of the newly hatched Necturus are accurately and 

 certainly elicited when the animal is hungry, as Whitman showed, but 



* Whitman, "Animal Behavior," Marine Biological Lectures, 1898. 



5 Pike, Quarterly Journal of Experimental Physiology, 1913, VII., pp. 22-26. 



5a Cannon, Harvey Lectures for 1911-12, pp. 130-152, Philadelphia. 



