^^^ younial of Comparative Neurology and Psychology. 



fifth day and is based on the records of the preceding five days. 

 Some very interesting things are brought out in this table. At 

 first the environment was new to the rats and everything was 

 strange. No attempt was made to show them the way to the 

 food nor to the nest box. As a result they did much more work 

 at first than later when they had become accustomed to their 

 surroundings. This accounts for the apparent decrease in activity 

 from an average of 121 revolutions on the fifth day to 26 on the 

 fifteenth day. From this time on there is an almost constant 

 increase in the daily activity. It is especially noticeable toward 

 the termination of the experiment. 



TABLE v. 



Average number of daily revolutions. 



This experiment coincides so far as it goes with the results 

 obtained in the former experiments. It shows that the period 

 of greatest activity, as measured by the number of revolutions,, 

 for these four rats has not been reached at the age of 84 days. 

 Whether the average age of greatest activity would be greater 

 or less than that determined by Experiments I and II can not be 

 determined from these results. It could only have been ascer- 

 tained by continuing the experiment. The experiment now under 

 way should make this clear. 



CONCLUSIONS. 



1. White rats of different ages show a marked difference in 

 in their activity. 



2. The very voung rat and the old rat are each noticeably 



