Jason Gresh, age 8, of Staten Island, N.Y., for his question:

IS THE DOLPHIN REALLY INTELLIGENT?

Many people are confused when they talk about the dolphin and the porpoise. Which is the smart guy who performs often in water shows? The way to tell them apart is to notice that the dolphin has a beaklike nose and the porpoise does not. Both are small, whalelike mammals, but the dolphin is the intelligent showman with a knack for entertaining people.

There are two types of dolphins: the bottle nosed dolphin and the common dolphin. Star in many aquarium shows is the bottle nosed dolphin who can quickly learn tricks such as swimming in a pattern, stopping quickly, making sharp turns and leaping high into the air. He can also jump through a hoop and fetch a stick or ball.

Scientists agree that the dolphin is one of the world's most intelligent animals. He rates between the chimpanzee, who is considered to be the most intelligent animal, and the dog. He has excellent eyesight and hearing.

Dolphins seem to communicate with each other by whistling, barking and clicking. And they have even been able to imitate some of the human speech sounds. Sound originates when the animal blows air through passages which are ordinarily used for breathing. The passages lead to the blowhole, which is an opening at the top of the head. The dolphin's air passages and blowhole have flaps of muscles that move to make various sounds.

During the 1950s and 1960s, extensive experiments were conducted by an American doctor named John C. Lilly. Because the dolphins had high intelligence, he and others believed there might be some way for man and dolphin to communicate with each other. The experiments, however, failed to develop any proof that there can be an intelligent exchange between the two.

Dolphins have a natural sonar system called echolocation which allows them to locate underwater objects. They make sounds and then listen to the echo.

The bottle nosed dolphin can be found in most of the world's coastal waters. He grows to be up to 12 feet long and weighs up to 800 pounds. His beak is about three inches long, and he has between 80 and 88 teeth. He is gray with light color on his underside and darker on top.

The common dolphin is found only in warmer ocean waters. Not quite as smart as his bottle nosed cousin, he grows to be seven feet long and weighs up to 150 pounds. He's black on top and white on the underside, with colorful white and brown stripes running on his side.

For hundreds of years, men of the sea have considered the dolphin to be lucky. Schools often follow ships and extend what seem to be greetings. Even though dolphin meat is delicious, most sailors refuse to kill them.

Dolphins were mentioned in Greek and Roman mythology. The Greeks thought they were sacred to the god Apollo.