| Ants are sightless creatures, although they do have | | | | but in order to get unerringly to its prey it must keep it |
| eyes that distinguish between light and dark. However, | | | | in clear vision during the descent. If we humans were |
| they find their food and mates by a sense of smell | | | | to move as rapidly toward something five hundred |
| located in their antennae. Another sightless creature is | | | | feet away, the iris in our eyes would have to change a |
| the tapeworm, dwelling inside the human body, where it | | | | great deal for us to keep the object in clear vision the |
| does not need sight. There are many sea creatures, | | | | entire way, which sometimes explains why some of |
| such as oysters, that have no true eyes, but that are | | | | us can experience sight-loss when running very fast, |
| so sensitive to light that a shadow passing over them, | | | | our vision becomes blurred and erratic. |
| or approaching, will lead them to seek safety by | | | | This what the iris of the hawk does, but it does it so |
| withdrawal into their shells. Long before man had the | | | | rapidly that it is difficult to understand how it can keep |
| idea of protecting his eyes with wind glasses or a | | | | in focus on a tiny rodent in the few seconds of a rapid |
| windshield, the camel was using his own windshield on | | | | dive. This speedy change of focus enables birds to |
| his eye to keep out the sand. This desert animal is | | | | catch insects on the wing with amazing dexterity. |
| equipped with a sort of third eyelid, which may be | | | | Some birds' eyes also are equipped with a sort of |
| drawn down at will over the eyeball without impairing | | | | sunglass lens, which enables them to look directly into |
| the sight. | | | | the sun without injury to the eye or impairment of |
| Birds have this third evolid, also, enabling them to fly | | | | vision. The eye is a remarkable mechanism in any |
| into the wind. And birds have other marvelous | | | | case, the human eye being able to accomplish |
| characteristics in their eyes unequalled by other | | | | amazing things and sustain great punishment without or |
| creatures. A hawk or vulture, for example, may spot a | | | | with the aid of the optician. And elsewhere in Nature |
| small animal on the ground far below whilst it spends | | | | the eyes of many creatures have been marvelously |
| its' days on the look-out for food. It goes into a dive, | | | | adapted to a wide variety of specialized needs. |
