Emilie Fowler, age 7, of Winston Salem, North Carolina, for her question:

How are seashells made?

Seashells come in thousands of pretty shapes and colors. They are made by little creatures that have soft bodies, somewhat like clams or snails. The sea where they live is full of hungry enemies. So the helpless little creatures build sturdy shell houses and hide themselves safely inside. Each one of them has a loose flap of special skin wrapped around his body. This is the remarkable mantle that forms the shell.

The salty sea teems with all sorts of dissolved chemicals    and each little shell builder takes this water into his body. His mantle sifts out calcium and other building materials it needs. It changes these chemicals into other ingredients. Then it oozes a layer onto the inside of the shell, plus a different ingredient to make it set hard. The little creature keeps on adding layer by layer to make his shell thicker and larger.