EYES THAT SHINE AT NIGHT WALKER 353 



A few animals, notably the binturong and the golden cat, close their 

 eyes very quickly when the beam of light is directed at them. Most, 

 however, stare directly at the light or move the head only slightly. 



Of the monkeys, no shine was detected from the eyes of orangutans, 

 chimpanzees, gibbons, macaques, langurs, baboons, and marmosets. 

 A faint suggestion of a shine was detected in the ring-tailed lemur. On 

 the other hand, the eyes of the slow loris and the potto gave the most 

 brilliant reflections of all eyes observed. Mr. A. J. Van Rossem once 

 told me he had seen the eyes of spider monkeys shine. 



My observations suggest that the majority of rodent eyes shine but 

 dully in browns, hazel or amber, but the porcupines are an exception — 

 their eyes are very brilliant — generally silvery and reflecting through a 

 wide angle. 



In the case of snakes, one is sometimes tempted to mistake the shine 

 from the surface of the scale over the eye (the brille) for the true reflection 

 of the eye. 



These studies have been more fruitful of unsolved questions than of 

 answers. Some of the questions are: 



1 . Do the animals possess vision over a wide cone or only over that 

 cone in which reflections may be obtained? If the former is the case, 

 it indicates that such animals as the hippopotamus and Old World 

 porcupines can see in practically any direction except for a narrow 

 angle directly behind them. Others have a very narrow angle of vision. 



2. What is the difference between eyes that shine and those that do 

 not? 



3. What produces the different colors of reflections? 



4. What changes take place in an eye that cause it to give differently 

 colored reflections in quick succession? 



5. What is the explanation of the fact that eyes that do not change 

 colors quickly give quite different colored reflections on different dates? 



6. Why do some eyes that give reflections at a distance beyond 8 

 to 10 feet fail to give any when viewed at a lesser distance? 



In the following list the occurrence of the letters C, or C. and E., 

 indicate that the observations were made by Jeremiah A. Collins or 

 Collins and Arthur L. Edwards, National Zoological Park policemen, 

 while on night duty. This opportunity is taken to thank them for 

 their assistance. The mark / between notes indicates different dates 

 of observation. Some of the animals have been observed many times. 

 The figures in parentheses indicate the number of individuals observed. 



MAMMALS 

 Maksupialu 

 didelphidae: 



Virginia opossum (Didelphis vhginiana) Dull orange. 



Zorro or banana opossum (Metachhus opoi- 



sum).. Silvery to pale amber. 



macropodidae: 



Tree kangaroo (Dendrolagut inustus) (2) Dull deep red amber. / Deep reddish orange. / Red 



dish orange and blood red. 



