The brain of Nereis has a diversity of endocrine actions on processes associated with growth and sexual reproduction. Regeneration-promoting, maturation-inhibiting, and gametotrophic activities have been studied by transplating brains from animals at various stages of the life cycle into decerebrate, immature hosts. Endocrine activity declines greatly during gametogenesis. In animals approaching sexual maturity, maturation-inhibiting activity is extinguished, whereas a low but significant level of regeneration-promoting activity, and gametotrophic activity, is retained. The close correlation of these activities supports their postulated mediation by a single hormone, although the processes subject to endocrine control show different thresholds for hormone action.

No abstract