Mary Christensen, age 11, of Harlen, Iowa, for her question:

How many different kinds of fish are there?

So far the experts have named and classified more than twenty five thousand different fishes   and from time to time a new specimen is discovered. This means that there are as many different fishes as there are different mammal, amphibians, birds and reptiles altogether. And these are all true fishes. This number does not include the starfish, the shellfish, the jellyfish and the countless host of other sea dwellers.

A true fish is a backboned animal. He has fins and almost always he has scales. `He has gills for taking dissolved oxygen from the water, though certain fish can manage without water for days or even longer. With rare exceptions the fish is a cold blooded animal and without exception his natural home is in the water.