CONTENTS. 



Page 



Acknowledgments -------------------- 3 



Introduction- --------------------- 4 



Eistorical- ---------------------- 4 



Apparatus and Trocedure ---------------- 9 



Sxpariiiisivoal Rssulta -- -----------------21 



Twenty-five day rats ---------------- 24 



Sixty-five day rats- ---------------- 34 



TWO hundred day rats ---------------- 33 



Three hundred day rats --------------- 43 



Five hundred day rats- --------------- 49 



Comparison of Results for Different Ages- ------- 54 



Incidental Tests; — d9 



Effect of Sex on Rapidity of Learning- ------- 59 



Day and Night 'rVork ----------------- 62 



Continuation of ."ork after Iroblem has been Learned - ^3 



Blood Relationship and Learning _--____-- qq 



Retention- --------------------- 70 



Resume of Conclusions ----------------- 72 



Biography- ---- — — ___-.----_-. -- 74 



