244 journal of Cojuparative Neurology and PsycJioIogy. 



sure that in the interval which had elapsed between the beginning of 

 this portion of my work and its completion no important changes in 

 the plasticity of the race had occurred.^ As a matter of fact this 

 precaution proved unnecessary, for no important differences appeared 

 as the result of the interruption of the investigation. 



The condensed results for the four-month individuals appear simi- 



TABLE 4. 



Relation of Age to Modifiability of Behavior 

 White-black Discrimination Habit 



* Twelve months old. 



larly in Table 2, and those for the seven-month individuals in Table 3. 

 In the ten-month group (Table 4) I have included the results for 

 three mice which were twelve months old. Although it is not wholly 

 satisfactory to do this, it seemed better than to deal with the three 

 individuals separately. At any rate nothing is concealed by averag- 

 ing the results for the ton mice, for the individual results are avail- 

 able. 



To make comparisons easier, I have brought together in Tal)le 5 



"An epidemic \Yliicli destroyed almost all of my mice caused a delay of 

 over a year. 



