ROBERT M. YERKES 



Explanation of Plate II 



Figure 3. — Orang utan, Julius, reaching for banana. 



Figure 4. — Julius walking across his cage. 



Figure 5. — P. rhesus, Sobke. 



Figure 6. — Sobke stretching his jaws (yawn?) preparatory to 



a fight. 

 Figure 7. — P. irus, Skirrl. 

 Figure 8. — Skirrl using hammer and nail. 

 Figure 9. — Skirrl using a saw. 



