Hob Davies age 13, of Phoenix, Ariz. for his question

 What exactly is a sponge?

Most sponges on the market today are copies of the natural sponge found squatting on the floor of some tropical sea. The imitations are made from frothy batters, some of natural substances such as cellulose or rubber, and some of man‑made plastics such as viscose or vinyl, These artificial sponges are good cleaner‑uppers; But the natural sponge ‑is even better and more durable, It looks like some form of plant life. But actually it is the horny skeleton from one of the strangest animals in the world. The animal kingdom is classified in large groups called phyla and each phylum is subdivided into smaller divisions. The phyla are listed in order from the simple protozoa to the complex backboned animals. Most of the complex animals resemble the simpler animals in some way, We often can see how a complex animal developed from more simple ancestors. We can trace countless family trees. But we cannot trace a family tree for the sponge, He resembles no living animal and his ancestors are unknown.

There are some 3,000 different sponges and they have a phylum all to themselves, They belong to the Porifera phylum, meaning the pore bearers. A few tiny sponges live in fresh water but most of them live in warm ocean waters. The living sponges look even more plant‑like than their useful skeletons, They resemble bushes, trees, cups and cactus plants,

The adult sponge never moves from one spot. He has no legs and no heady no mouth and no lungs or gills, no blood and no heart, As he sits there, his tough skeleton is nowhere to be seen. It is covered with fleshy cells and a dark, slimy skin.

The sponge has no senses and no nervous system. He will feel no pain if you slice him apart.

The inside of the living sponge looks very much like raw liver. It is a mass of very simple cells clustered around a system of tunnels and supported by a firm skeleton. The slimy rind of the sponge is a 1 ayer of tough, flat cells. A constant stream of water, bearing oxygen and fragments of food, circulates through the body. This water enters through tiny pores in the skin. It is forded back into the ocean from a deep tunnel in the center of the sponge. The tunnel walls are lined with special cells. Each bears a small thread or tail set in a collar of belly. Countless numbers of the little tails wave and keep the water circulating.

The cells of the inner tissue are soft and each one is a Jack of all ­trades. It can digest food, take oxygen from the water, repair damage and maybe even produce an egg. These cells also can take the necessary minerals from the sea and use them to build the skeleton. Some sponges make glassy skeletons of silicates. Some make rocky skeletons of calcium carbonate. The sponges we find useful make their skeletons from a tough, horny protein material called spongin. When a sponge gets to market, all the soft tissues are stripped away and only the spongin remains,