Jason Mitchell

The organization of the echinoderm central nervous system (CNS) is striking because it varies widely from that of other bilaterians; however, the basis for this is unknown. In the present paper, I identify echinoderms as compound and I show that this is the basis for their radial symmetry and the organization of their CNS. The asteroids, as I show, comprise of bilaterally symmetrical zooids arranged radially. Furthermore, I show that segmentation is the mechanism by which the gene Sonic hedgehog (Shh) bifurcates and duplicates patterning.