Fig. 11

Summary diagram of the ontogeny of catecholamine containing structures in P. dumerilii. The first CA cells cp1,2 appear in early trochophores slightly behind the prototroch. Their basal fibers run into the prototroch nerve, and by the late trochophore stage, they outline the prototroch nerve, pretrochal part of the ventral nerve cord and brain commissures. In metatrochophores, two more cells cv1,2 appear and by the late metatrochophore stage, the fibers of these cells outline the brain and brain commissures, prototroch nerve, ventral cord and three transverse commissures corresponding to larval segments. Starting from the nectochaete stage, more cells and neurites add in the developing central and peripheral adult nervous system. Apical end is always up. Relative dimensions are not maintained