Danny Pay, age 11, of Niagara Falls, Ont., Canada, for his question:

DO SNAILS BUILD THEIR OWN SHELLS?

The embryo snail develops in a small, round egg. The embryo shell is there, like a tiny flake, before he hatches. It remains attached to his back and, as he grows, it grows with him. The shell material is created by fleshy flaps called the mantle. New material is added around the edges for the shell is the snail’s house and it must be large enough for his body. Yes, he builds his own house and keeps the same one throughout his life.