misleading. Many have thought, and the 

 impression still prevails, that this light 

 is of a phosphorescent character, while 

 others seem to think that the glow is in- 

 herent, so that the eyes of the animals 

 possessing it will shine after dark or in 

 an unlighted room at night regardless of 

 any independent source of light. 



Both of these views are, of course, 

 wholly erroneous, since the illumination 

 seen in such eyes is merely the reflection 

 of rays generated beyond the animal and 

 visible to the observer by reflex action. 

 Two disks of tin, the size of a five-cent 

 piece, fastened a few inches apart on the 

 trunk of a tree will so reflect the light 

 from a hunter's lantern as to deceive all 

 but the most expert, and the writer has 

 frequently used this method for detect- 

 ing or misleading market hunters and 

 others shooting at night in violation of 

 law, for this destructive method is now 

 prohibited in nearly all the States. 



At the present time, however, "jack- 

 ing," as it is usually called, has come into 

 effective use in collecting scientific speci- 

 mens or as an aid in the taking of flash- 

 light pictures of wild life at night. Since 

 most animals, big and little, are noc- 

 turnal, by using a light that will cause 

 their eyes to glow it is now possible to 

 get many specimens or photographs 

 otherwise difficult to obtain and at the 

 same time to use the night hours for this 

 work, thus greatly increasing the oppor- 

 tunities and affording more favorable 

 conditions for photography. 



Originally, when hunting and later in 

 night photography, the writer became 

 familiar with many animals whose eyes 

 glowed before a light as well' as with 

 those that did not have this peculiarity. 

 For a long time it did not suggest any 

 extended investigation, and beyond not- 

 ing the different species, their actions 

 under the light, and the variance in color 

 reflection, nothing was done toward de- 

 termining the portion of the eye that 

 caused such reflection, whether it per- 

 formed any function or was merely an 

 arbitrary or useless attribute, without 

 value or significance in the classifica- 

 tion of different families and species of 

 animals. 



WHY ANIMALS CAN SEE AT NIGHT 



In considering eye reflections, they 

 should not be confused with the glisten- 



BUZZARD FIRING FLASHLIGHT IN DAYTTME 



The left wing became involved in string tied 

 to bait and half of the pinion feathers were 

 pulled out. These birds became such a nuis- 

 ance' that when meat bait was used the flash 

 was not set until dusk. 



ing surface so characteristic of all eyes, 

 human or otherwise. The exterior light 

 is mirrored on a posterior, lustrous layer 

 of the retina, next to the choroid coat, 

 called the Tapetum luciditm, and appears 

 as a bright, luminous glow, which, in the 

 case of many large animals, can be seen 

 on a dark night, with a powerful lantern, 

 ioo yards or more away. Such glowing 

 orbs have usually the brightness and 

 steadiness of a star or a ball of fire, and 

 can generally be detected long before the 

 body of the animal becomes visible under 

 the approaching light. 



While it is impossible to give here in 

 detail the writer's investigations, they 

 may be summarized by stating that the 

 eyes of all the carnivorous or predacious 

 animals glow, as is the case with their 

 domestic descendants, the cat and dog. 

 The same is true of practically all the 

 hoofed or grazing animals and many 

 other families, while on the other hand 

 the two great orders — the Primates, in- 

 cluding man, apes, monkeys, etc., and the 

 Rodents — have few species that possess 

 the tapetum. In addition to the mam- 



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