Gail Bier, ago 9, of Seattle, Washington, for her question:

 How does a starfish grow a new arm?

Sometimes the simple animals can outdo the more complex creatures. A starfish can grow a new arm, but a monkey cannot. A lizard can grow a new tail, but a dog cannot. And, of course, if a human being loses a leg, it is gone, for good.

We do not know exactly how some simpler animals can replace a lost limb or tail. If we did, maybe we could copy this valuable trick. All we can do is watch this marvelous regrowth as it takes place.

The starfish. can replace any one or all five of its pretty, tapering arms. And a starfish is likeily to lose an arm from time to time. The arm may break off at the tip, part way down or at the root. Regrowth starts at the broken end of the arm.

It begins almost at onto as a little bud. The bud grows and forms a miniature copy of the lost arm. It keeps growing until the now arm is a perfect copy of the old. The whole process takes but a few weeks in the life of a starfish.