9 2 



The Dancing Mouse 



ably has markedly different effects upon the retinal elements 

 of the eyes of unlike organisms. In a study of the sense 



of sight it is 

 extremely impor- 

 tant to discover 

 whether difference 

 in the quality, as 

 well as in the in- 

 tensity, of a visual 

 stimulus influ- 

 ences the organ- 

 ism; in other 

 words, whether 

 color sensitive- 

 ness, as well as 

 brightness sensi- 

 tiveness, is pres- 

 ent. If the dancer 

 perceives only 

 brightness or lu- 

 minosity, and not 

 color, it is evident 

 that its visual 

 world is strikingly 



FIGURE 14. Discrimination box. W, electric-box different from 

 with white cardboards; B, electric-box with black card- that of the normal 

 boards. Drawn by Mr. C. H. Toll. t - 



human being. 



The experiments now to be described were planned to show 

 what the facts really are. 



As a means of testing the ability of the dancer to distin- 

 guish differences in brightness, the experiment box repre- 

 sented by Figures 14 and 15 was devised. Figure 14 is the 

 box as seen from the position of the experimenter during the 



