38 



HELEN B. HUBBERT 



Figure 6-c Distance Curve for Three Hundred Day Rats 



There was almost no difference between the learning of the 

 males and that of the females, such difference being even less 

 marked than in the twenty -five day group. The averages are: 



Time 



Five Hundred Day Rats 



Records on only eleven rats have been obtained in this group, 

 six strains being represented by four males and seven females 

 who began the problem when five hundred days old. These 

 rats like the 300-day animals, were fed in the maze for ten days 

 previous to the commencement of the problem, and allowed to 

 eat for from six to eight minutes at the close of each day's work 



