A PHYSIOLOGICAL APPROACH TO THE 



RELATION BETWEEN PREY AND 



PREDATOR ' 



By K. D. ROEDER 



Department of Biology, Tujts University, Medford, Mass. 



(With 5 Plates) 



BEHAVIOR AND EVOLUTION 



The description of animal behavior in terms of its underlying 

 neuronal organization preoccupies an increasing number of workers. 

 Human egocentricity naturally dictates that much of this work be 

 done on the higher vertebrates, but the extreme complexity of the 

 problem at this level has so far limited tangible results to the simplest 

 reflexes. Difficulties are due not only to the size of the neuron popu- 

 lation which mediates behavior in the higher animals, but also to the 

 increasing plasticity of their behavior. 



The student of behavior mechanisms faces problems whose general 

 nature is surprisingly like those encountered in searching for the or- 

 ganic basis of evolution. In a stimulating essay Pringle (1951) points 

 out the analogy between the evolution of a species through selection 

 and the appearance of behavior patterns in an individual animal 

 through learning. In the course both of evolution and of learning the 

 trend is toward complexity and organization and away from random- 

 ness. In the evolution of body form the increase in complexity is 

 structural, while in learning the complexity has a temporal dimension. 

 Species within a genus or genera within a family differ in appearance 

 by a number of modifications of recent acquisition and have in com- 

 mon, as a group characteristic, a relatively immutable core of more 

 anciently acquired body organization. Similarly, individuals of a spe- 

 cies may differ from each other in their behavior by response patterns 

 learned during their respective lifetimes but they still share a core of 

 innate drives or instincts characteristic of the species and ancestral 

 in origin. To extend the comparison further it could be pointed out 



1 The experimental work reported in this paper was made possible by Grant 

 E.947 from the U.S. Public Health Service, and Grant G.1304 from the National 

 Science Foundation. Some of the equipment was purchased under a contract 

 between Tufts University and the Chemical Corps, U. S. Army. 



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