GENERAL MEETING. 13 
Mr. S. M. Burnett made a communication entitled 
WHY THE EYES OF ANIMALS SHINE IN THE DARK.* 
[Abstract. ] 
Erroneous opinions have been held and expressed, not only by 
the non-scientific, but also by some persons holding high positions 
in the scientific world, in regard to the phenomena of luminosity of 
the eyes of animals, and particularly of cats, when they are in ob- 
scurity. It is not due, as has been commonly supposed, to phosphor- 
escence, but to light reflected from the bottom of the eye, which 
light is diffused on account of the hypermetropic condition that is 
the rule in the lower animals. 
In response to a question by Mr. White, Mr. Burnerr said that 
human eyes affected by hypermetropia do not yield similar results, 
partly because the human pupil is too small and partly because the 
bottom of the human eye is not so strongly reflecting a surface as 
that of most animals. 
Mr. Harkness remarked that in determining the degree of di- 
vergence of rays emitted by an eye, from an image situated upon 
its retina, it is necessary to consider the magnitude of that image 
as well as its distance from the focal plane of the lens. The diver- 
gence of the rays coming from any one point of the image is deter- 
mined by the interval which separates the retina from the focal 
plane of the lens, while the divergence of the rays coming from 
any two points of the image depends principally upon the size of the 
image itself. The total divergence is the sum of the divergences 
produced by these two causes, and the neglect of that due to the 
size of the image will probably account for the discrepancy between 
the observed angle of divergence and that computed by Dr. Burnett. 
It also seems desirable to bear in mind the distinction between 
fluorescent and phosphoresent light ; the former disappears as soon 
as the incident waves are cut off; the latter does not. 
* This paper is published in full in the Pop. Sci. Monthly for April, 1884; 
Vol. XXIV, pp. 813-818. 
