Sea urchins have long been used to study morphogenesis and cell fate specification and are an established model system in developmental biology (1 ). Most contemporary studies have focused on early development, however, and few molecular genetic studies have examined larval development, or the formation of the highly derived radial body plan of the adult (2 ). A better understanding of the molecular genetic basis of both the body plans of this phylum may contribute significantly to several fields of biology (3 ,4 ).
