ABSTRACT
Caudal regeneration in Nereis diversicolor is that rapid proliferation of segments which occurs after loss of part of the posterior of the body and the reformation of the pygidium. The rate of segment proliferation is highest during the production of the first new segments. Thereafter, the rate declines rapidly with each passing week, though if the regenerated segments are amputated, rapid proliferation is again resumed (Golding, 1967). Two explanations of these results are possible. First, the declining rate of segment proliferation during regeneration may be the result of a declining concentration of hormone in the body fluids. There may be a feed-back from the regenerating tail to the ganglion. As segments are proliferated, the secretory activity of the ganglion is suppressed. Secondly, the level of hormone in the body fluids may remain constant, the proliferating region of the pygidium becoming progressively more insensitive as regeneration proceeds.
