Page 121 - Miracle in the Eye

Eyelids
There are vast differences between a reptile's eyelids and the eyelids of
other creatures. It may appear as if snakes do not have eyelids, for example,
but their eyes are in fact covered by an immobile, transparent layer of scales.
Lizards, on the other hand, have movable eyelids. But in the desert
lizard especially, the eyelids are upturned. This keeps out the sand, prevent-
ing it from harming the eye when the lizard buries itself in the sand.

The Sensitive Eyes of a Frog
Recent research has revealed some of the frog's eye's interesting abili-
ties. One kind of retinal cell responds strongly to small, dark, round moving
objects and is most active when those objects moved irregularly. It is as if the
neurons of the frog eyes were designed especially to detect flies. Some sci-
entists call their eyes "bug detectors." 49

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