Jeffrey Luzius, ago 8, of Indianapolis, Ind., for his question:

How do animals eyes shine in the dark?

Eyeshine is Mother Nature’s gift to a few night prowling animals. It helps them to see in the dim light. On starry nights the eyes of the soft feathered owl glow like embers. So do the eyes of the soft‑footed cat. The eyes of curtain moths also gleam in the night as do the eyes of certain night prowling spiders.

In total darkness, however, there is no eye shine from these night wanderers. The glowing light we see is a reflection. You cannot spot it unless there is a little moonlight, starlight or a light is flashed.. For eyes gifted with eye shine act as reflectors. They are like those little glassy buttons on highway signs. We do not notice them in the daylight and in pitch darkness we cannot see them at all. They glow, spelling out their messages, when they reflect the headlights of a car.

Eyes gifted with eye shine have a special layer of reflecting tissue The retina in a normal eye is a dark screen at the eye's beck. Light passes through the pupil and carries an imago of the scene onto this retina. Nerves carry the picture to the brain. The light carrying the picture is absorbed by the retina. The shiny layer of tissue behind the retina of the eye gifted with eye shine bounces some of the light back from this built‑in reflector. So, the light makes a double journey through the retina instead of being absorbed as in the normal eye.

This means that the nerves carrying the picture get a double dose of light. The darker patches of the imago are darker, the lighter patches are lighter. The animal with normal eyes gets a dim, blurry picture when in a dim light. The animal with eyeshine guts a picture twice as bright, little mouse, wandering around at night, can see hardly at all. The owl and. the pussycat can see almost twice as well.

The shiny tissue has done its work when the light is reflected back through the retina. However., it does not stop then. Some of it continuous on through the pupil in front of the eye. This is the lightwe see as eyeshine.

It has been through the pupil and the retina to the layer of reflector cells behind the retina. There it bounces and comes buck through the retina and out again through the pupil.

Eyeshine is the light left over from the process which helps an animal to see better in a dim light. It is no help to the animal at all. In fact, it is a nuisance. For those glowing eyes are a giveaway. Often you would not s©e a cat in the dim light at all if it were not for those glowing eyes.

Mother Nature gave certain animals those wonderful eyes to help them hunt at night. However, she evened up the score a bit. She added glowing eyeshine so that their victims could see them and take warning.