350 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 3 8 



retina as revealed to them through the opthalmoscope. These pic- 

 tures, however, might be compared to the view that would be obtained 

 by standing outside a dark room and projecting a beam of light onto 

 the walls of the room, thereby revealing the color and other features 

 of the walls to the observer standing outside. This is quite different 

 from the "shining" of eyes, which merely brings back toward the 

 observer diverging rays of colored light like small incandescent lights 

 seen from a distance. 



Information on the "shining of eyes" is so meager that it appears 

 justifiable to record my observations in the hope that someone may 

 be able to use them as a foundation for further studies. While eyes of 

 animals in the wild are frequently observed at night, the name of the 

 owner of the eyes is often unknown, and there is little likelihood that 

 the same individual can be observed again under similar conditions. 

 A zoo is unexcelled for this purpose as it permits one to study many 

 different kinds of animals under more or less constant conditions and 

 to observe repeatedly the same individuals. 



In obtaining my observations I used a reflecting head lamp, similar 

 to a hand flashlight, worn on my forehead connected by a cord to a 

 three-cell battery in a pocket or on my belt. Flashlights carried in 

 the hand were used at times but were not entirely satisfactory as the 

 rays of the light must closely parallel the line of sight of the observer 

 in order to obtain reflections from the greatest number of species and 

 uniform results. The best results are obtained with a light of moder- 

 ate intensity. If it is too bright, the shining is less conspicuous or 

 does not show at all. Four main points are observable in every case. 

 They are: 



(a) Whether or not the eyes reflect light. 



(6) If they reflect, the color of the reflection and whether the color 

 is individually constant or variable; also whether or not it varies in 

 different individuals of a species. 



(c) Whether the reflection is dull, medium, or brilliant. 



(d) The angle from which reflections are obtainable, i. e., whether 

 it is necessary for the observer to be opposite the center of the eye, 

 or if the reflection can be obtained from behind the animal and in 

 front of it, as well as directly opposite the center of the line of vision. 

 This might be considered as wide or narrow angle of reflection. 



For the sake of brevity the data given in the appended list relates 

 almost entirely to observations on (b) and (c). 



The description of colors in words and the indication of varying 

 degrees of brilliance or paleness are so difficult that the observations 

 herein recorded can in general indicate only relative differences 

 between animals. 



The word "glow" is sometimes used to describe the character of 

 the reflections. This term can well be used for the reflections given 



