COLOR BLINDNESS OF CATS 



121 



their tops pressed closely against the under surface of the top- 

 board, so that the animal must select the glass at which he 

 pulled by its outside appearance only and without being able 

 either to reach into it or look into it until he had pulled it down. 



Figure 1. A. Apparatus for displaying the glasses which were tinted with col- 

 ored papers. B. Cat depressing lever to release food-glass. C. Cat looking 

 over the top of the apparatus in order to discriminate by the positions of the 

 thumb-buttons. 



By means of the thumb-buttons at the rear of the apparatus 

 every glass except one was locked against the topboard. A pull 

 at the glass which was on the free lever depressed its short arm 



