WHEN this strange animal is a baby, it is no larger than a pea. As the baby grows, it needs a larger house. It does not build a new one, but it makes the old one larger.
The sea-urchin's house is not made of one part or even two. It has five or six hundred pieces in its shell. These pieces are beautifully joined.
The shell is covered with green and purple spines. These spines make the sea-urchin look like a huge burr. They are very useful, for they protect it from its enemies.
It has many feet arranged in rows. The feet are little tubes with suckers at the ends. The sea