Dee Dee Hicks, age 15, of Gallup, N.M.) for her question:

WHAT IS A JELLYFISH?

Jellyfish are from a group of animals called coelenterates. That's the fancy, scientific name to describe a group of creatures who have bodies made of only two layers  an outer surface called ectoderm and an inner called endoderm.A jellylike substance between the two layers gives form, and also its name.

Jellyfish are not made out of jelly, as you have probably guessed, nor are they fish. They are simple, transparent sea animals that vary in size from an inch to more than 10 feet in length.

Jellyfish do not have backbones or skeletons. Their soft bodies are often shaped like umbrellas. Around their outer edges are stinging tentacles which are used for getting food. Swimmers in the ocean have sometimes received severe stings from certain kinds of jellyfish.

The stinging cells of the jellyfish are called nematocysts. They can paralyze small organisms which the tentacles then bring into the jellyfish through a center opening.

Jellyfish propel themselves by squirting jets of water from their central openings while contracting their bulk. Water is expelled downward and the animal moves upward.

Also located around. the rim of the creature are a number of sense organs, some of which act as simple eyes and some as organs of balance.

Jellyfish are sometimes called medusae because their fringe of tentacles looks very much like the snaky tresses of Medusa, a monster from Greek mythology. On the jellyfish who measures 10 feet across, his.tentacles can be as much as 100 feet long and the big monster can weigh as much as several tons.

One type of jellyfish is called the Portuguese man of war.  He's found in the North American Gulf Stream and is iridescent in many beautiful colors. He is balloon like since he floats on top of the water and trails his long threadlike tentacles behind him.

A close relative to the medusae are the comb jellies. They have eight rows of comblike swimming plates arranged along the body from the mouth to the opposite end. It is by these plates that comb jellies swim and maintain an upright position. When stimulated, the comb jellies carry out a chemical reaction within themselves that produces a brilliant cold light.