The Effect of Delayed Brain Extirpation and Replacement on Caudal Regeneration in Nereis diversicolor

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Abstract
Extirpation of the supra-oesophageal ganglion of Nereis diversicolor before or up to 48 hours after amputation of a number of posterior segments inhibits caudal regeneration. Extirpation of the ganglion 3 or more days after amputation of segments retards but does not inhibit regeneration. Injection or implantation of supra-oesophageal ganglia of regenerating worms into decerebrate hosts 48 hours or more after amputating the posterior segments results in segment proliferation in some of the recipients. Replacement of ganglionic material before 48 hours has no effect. The types of regeneration observed following replacement therapy on the 3rd or 4th days is characteristic of that when there has been a limited migration of coelomic cells to the wound. ‘Regeneration’ hormones appear to be present in the ganglion 48 hours after the loss of posterior segments, but they do not circulate in the body in effective quantity until 24 hours later.