Role of the Supra-œsophageal Ganglion during the Early Stages of Caudal Regeneration in Some Errant Polychætes

Abstract

THE importance of the nervous system in annelid regeneration has been realized for some years1, and it has emerged that, at least in lumbricid oligochaetes and nereid polychaetes, the supra-œsophageal ganglion secretes hormones that are essential for regeneration2–4. Durchon3 showed that if the supra-œsophageal ganglion of three species of nereid is removed regeneration is retarded. Hubl4 discovered that, in lumbricids, extirpation of the supra-œsophageal ganglion at the same time as a number of posterior segments is removed totally inhibits posterior regeneration, but that if the brain is removed 24–48 hr. after the posterior segments are amputated then posterior regeneration proceeds at the normal rate. There is thus a brief critical period during which the brain exerts its influence in initiating regeneration. Since Durchon extirpated the brain of his animals 24 hr. after amputating the posterior segments, it is not clear if the difference between his results and those of Hubl represents a real difference between lumbricids and nereids, or if it is due to the difference in experimental procedure.