Ann Marie Herndon, age 15, of Watertown, N.Y., for her question:

WHAT IS A COELENTERATE?

A coelenterate is one of a group of soft bodied animals. Included in the group are corals, sea anemones, jellyfish, hydras and hydroids. There are something like 9,000 different kinds of coelenterates, with most of them living in the seas of the world.

The word "coelenterate" comes from the Greek word that means "hollow intestine." Many of these animals have large digestive cavities.

The body of a coelenterate may be shaped like a cylinder, a bell or an umbrella. Every coelenterate has at least two layers of cells that form its body wall. An outer layer makes up the body covering and an inner layer lines the digestive cavity. Many of the animals have a third, or middle, layer of cells.

A medusa, or jellyfish, is a coelenterate that has a bell  or umbrella shaped body. A polyp is a coelenterate that has a body shaped like a hollow cylinder.