Tina Gale Wright, age 7, of Houston, Texas, for her question:

How can a dolphin breathe while he sleeps?

A dolphin, as we all know, is an air breathing mammal animal, He can stay below only as long as he can hold his breath. Then up he must pop to breathe out his stale air and refill his lungs with fresh air. He must do this through all his sleeping and waking hours. The mammals are highly developed animals with sensitive nervous systems and fine brains. They need more sleep than the simpler animals. Fishes need only rest periods and many simple creatures need no sleep at all.

The dolphin needs several hours of sound sleep every day. When time comes to take a nap, he lets his fat blubbery body float near the surface. He may be just under the water, head and all. But his body knows by heart just how to cope with the breathing habit. Every 10 to 20 minutes or so, it bobs up so that the dolphin's face is above the water. The dolphin breathes out and breathes in without even waking from his slumbers. Then down he dunks until time comes to take in the next breath of air.