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NENOZO UTSURIKAWA 



The females far exceeded the males in degree of savageness. 

 They were, moreover, surprisingly quick and aggressive, whereas 

 the males were either on the defensive or indifferent. Whether 

 this remarkable sex difference is correlated with the maternal 

 instinct is not clear. It is, however, noteworthy that in the 

 feeding behavior the male very obviously asserts himself and 

 becomes the aggressor. It further appears from these obser- 

 vations that the tendency to bite is not directly proportional 

 to activity. Instead, there seems to be a tendency toward an 

 inverse relation. 



The chief facts concerning savageness in the two strains are 

 these : 



(1) Females are much more savage (exhibit the tendency to 

 bite more often and persistently) than are males. 



(2) The inbred rats are much more savage than the outbred. 



(3) Individual differences exceed either sex or strain differ- 

 ences, and they are especially great in case of the females. 



EXPERIMENTAL OBSERVATIONS 

 The writer had intended to record the responses of his animals 

 to various stimuli and to more complex situations by means of 

 the galvanometer. But as the resources of the laboratory at 



