Kathy Williams, age 14, of Lyons, Kan., for her question:

HOW CAN WE TELL A SQUID FROM AN OCTOPUS?

This is no big problem for those of us who can count to eight and add two. The numbers refer to arms, or tentacles. Words that contain the letters "octo" are related to number eight. Hence, the octopus has eight arms, which leaves the squid with 10. However, there are other basic differences between these two cousins.

Both of these blue blooded mollusks belong to the seas. The squid is a fast restless traveler, usuallly in the company of countless friends and relatives. Together, a shoal of squids looks somewhat like a flock of speeding arrows. They depend on speed and numbers to escape sharks and other hungry enemies.

    The octopus is a timid character who prefers a quiet, rather lonely life. Instead of fleeing    in panic, he retires to a well hidden lair on the rocky sea bed. He is the brainiest of the backboneless animals and a master of    clever disguises. Unlike the clams, snails and other mollusks, neither the squid nor the octopus has an outer shell. The squid may have a fragment of shell inside his soft, boneless body; the octopus does not.

In both cases, the head and body are joined and held in shape by a sack of tough tissue called the mantle. The baggy octopus has a circle of eight twining tentacles, usually connected with flaps of skin to form a sort of umbrella. The barrel shaped squid is streamlined, with a pair of flat fins at his tail end. His head end is circled with eight medium length tentacles  plus a pair of extra tough longer ones, making 10.

Both the squid and the octopus swim by jet propulsion. Water is sucked in the front end and squirted out at the rear. Hence they swim backward, with tentacles trailing behind. Both have remarkable skins that enable them to change through a range of colors and combinations, including spots and blotches. Both have ink sacs and becloud the waters to bewilder their prey and confuse their enemies.

The 150 species of octopus and the 350 species of squid are so much alike that they are listed in the same class and  However, the basic differences make it necessary to classify them in different family groups.