Marilyn Stein, age 14, of Toronto, Ontario, Canada, for her question:

Why don't worms suffocate underground?

We are used to living in a wide, airy world and life below the surface may be hard to imagine. To us, the ground seems too solid to have room for any breathable air. True, if the ground happens to be a massive slab of hard granite, there are not many airy spaces. But even a hard rock usually has a few small pores and pockets    and wherever there are such spaces, they are filled with gases.

An earthworm does not live in solid rock, where air pockets are few and far be¬tween. He lives in the porous dirt, which is a hodge podge of solid crumbs with plenty of cracks and crannies between them. He needs only a small amount of oxygen and he absorbs it through the skin that covers his entire body. There is enough available air in the soil and plenty more in the tunnel he excavates through the dirt.