The color may vary from yellow to dark green, but within a single batch of eggs it is uniform. The egg is probably shed after the formation of the polar bodies. The eggs are fertilized as they are shed into the water. Cleavage is total and equal, closely resembling that of Asterias. A thickwalled hollow blastula is formed.
Gastrulation is by invagination.
A rotating blastula is formed in 10 to 12 hours, and a gastrula 18 to 20 hours after fertilization. At 48 hours, the rudiments of the arms are visible. At 96 hours, the first tube feet appear as small protuberances, and at 120 hours, some of the larvae are able to crawl along the bottom. They are completely covered with cilia which enable them to move slowly through the water. As they gradually elongate, the blastopore is displaced ventrally and the stomodeal depression becomes visible.