CHAPTER VII 

 THE SENSE OF SIGHT: BRIGHTNESS VISION 



THE sense of sight in the dancer has received little atten- 

 tion hitherto. In the literature there are a few casual state- 

 ments to the effect that it is of importance. Zoth, for example 

 (31 p. 149), remarks that it seems to be keenly developed ; and 

 other writers, on the basis of their observation of the animal's 

 behavior, hazard similar statements. The descriptions of 

 the behavior of blinded mice, as given by Cyon, Alexander 

 and Kreidl, and Kishi (p. 47), apparently indicate that the 

 sense is of some value ; they do not, however, furnish definite 

 information concerning its nature and its role in the daily 

 life of the animal. 



The experimental study of this subject which is now to 

 be described was undertaken, after careful and long- continued 

 observation of the general behavior of the dancer, in order 

 that our knowledge of the nature and value of the sense of 

 sight in this representative of the Mammalia might be in- 

 creased in scope and definiteness. The results of this study 

 naturally fall into three groups: (i) those which concern 

 brightness vision, (2) those which concern color vision, and 

 (3) those which indicate the role of sight in the life of the 

 dancer. 



Too frequently investigators, in their work on vision in 

 animals, have assumed that brightness vision and color 

 vision are inseparable; or, if not making this assumption, 

 they have failed to realize that the same wave-length prob- 



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