How does the embryo build itself? asks Dave McClay. It starts with a single cell containing the complete DNA instructions, but some cells develop into muscle and others into gut or skeleton. At the same time the cells have to communicate with each other, so that muscle cells join together to make a muscle with the right shape and in the right place. Sea urchins are ideal for this research. They are simple, but even better they are transparent; you can watch the structures form. McClay's student Cati Logan identified the protein that causes a ring of cells to become gut. They could force the protein into more cells or block it entirely; the embryo would develop too much gut or none. A Mediterranean species of urchin has eggs with a belt of pigment; remove the area below the belt and the embryo forms no gut. So the egg carries necessary information in the cytoplasm as well as the nucleus. But the best thing about sea urchins is, to get them you have to go to the beach. At the Marine Lab or in Southern France, for McClay, "Research is just plain fun."