Dawna Dikur, age 9, of Youngstown, Ohio, for her question:

How can a frog breathe underwater?

When the frog was a baby tadpole, he had a pair of fishy gills. He used them to take his oxygen from the water. Later he grew lungs inside his body and his fishy gills faded away. His lungs could breathe air but they could not take oxygen from the water. But perhaps somebody forgot to tell him this, for the funny fellow still sits for an hour or so down there under the water. Or perhaps he just holds his breathe until he must come up for air.

The truth is that the frog can still get oxygen from the water. And he can do it without using his lungs. He happens to have a very special skin that can take in oxygen from the water. The oxygen seeps through his thin moist skin to tiny blood vessels near the surface. He can stay down there as long as he likes. True, he lost his baby gills, but he can always take dissolved oxygen through his skin