Linda Carlson, age 12, of Sioux City, Iowa, for her question:

Is the octopus related to the fish family?

In one sense, we may call all the creatures who live in the sea and get their oxygen from the water, fishes. However, the true fishes have backbone The octopus has no bones at all. Strictly speaking, he belongs to the vast phylum Mollusca. You would never guess this from his appearance, but he is a distant relative of the quiet clam and the; dark‑blue shelled mussel.

The Mollusca phylum is divided into several smaller classes. One class is Gastropoda, the stomach‑footed ones. Mr. Slow‑Poke Snail is a gastropod. Another class is Cephalopoda, the head‑footed ones. This is the class to which the octopus and his cousins the squid and the nautilus belong.

The body of the octopus is a round bag of gristle with assorted tentacles arranged around the mouth opening. The tentacles also serve as legs. When Mr. Octopus goes walking along the floor of the sea, he is quite a sight. His legs are actually joined onto his head. Hence, it seems quite fair to call him a cephalopod, a head‑footed one.