Kathy Copeland, age l2, Of Houston, Tex., for her question:

Does an oyster have a heart?

The oyster has a neat little circulatory system with a heart, arteries and veins. The tiny heart has three chambers. Two of the chambers receive the blood as it flows back through the veins. The third chamber is a tough muscle which pumps the fresh blood out again through the arteries.

The blood of an oyster is colorless. It delivers oxygen to the living tissues and collects up waste materials. There is free oxygen dissolved in the water which passes through the gills of the oyster. From here it is taken by the blood stream back to the pumping heart.