Keith Blakley, age 14, of Orlando, Fla., for his question:

WHAT IS A SEA SQUIRT?

Sea squirt is the name for a group of sea animals which are also called ascidians. These animals have a habit of squirting out water through one of two body openings.

Adult sea squirts have leathery bottle shaped bodies. All their adult lives they remain attached to stones, shells and other fixed objects. Some live together in colonies.

The adult animal receives its food from water which it draws into the digestive tract through one of the body openings, the mouth. It then squirts out the water from the other opening, the atriopore.

Sea squirts go through a larval stage before they become mature. The larvae looks like a tadpole and can swim about. It has a notochord or elastic rod that extends through the tail. Because of this "backbone," scientists think sea squirts are related to the simplest fish like animals, lancelets and lampreys. In a few days, the larva loses its tadpole shape and settles on the ocean floor. Soon it develops its adult form.