28 D. B. CASTEEL 



be slight in amount. These results suggest that the discrimina- 

 tive faculty thus shown may have been an important factor in 

 the development of the mind of the growing turtle and that in 

 the common activities of its daily life the individual's behavior 

 may often be determined by its ability to appreciate differences 

 of direction, though but lightly marked, and to distinguish 

 accurately between slight differences of extent. 



