34^ 'Journal of Comparative Neurology and Psychology. 



After an interval of fifteen days it was interesting to note that 

 when they were first returned to the revolving cages they appeared 

 completely at home and within two minutes each had sought the 

 entrance to the nest box in the same manner as in Experiment I. 

 In going to and from the food box each showed its peculiar tricks. 

 This showed conclusively that the duration of memory for these 



Bevolutlon3 



7000 



5000 _ 



4000 



Days 



Fig. 4. Cun'es of daily activity of each rat for the same period as in Fig. 3. For simplicity tlie 

 average of each five days is taken. 



rats was at least fifteen days. Since the experiment was not 

 intended to follow along this line no further tests were made. 



In regard to their activity there was a very noticeable change. 

 No. I was exceedingly active, while No. 4 was very slow and 

 showed decidedly the effects of advanced age. No. 2 and No. 3 

 showed a degree of activity approaching that of No. 4. 



The marked differences in activity are best seen in the curves 



