Direct demonstration of the existence of a metabolic gradient in annelids

THREE FIGURES1. Regeneration method. Direct susceptibility method.* I n making a previous note on the use of methylene blue for demonstrating minor gradients (Jour.Exp.Zool., vol.24, p. 5 5 ) , the senior author, being a t that time ignorant of the fact, failed to credit Mr. John Wood MacArthur, formerly of this laboratory, with precedence in the use of this reagent, and takes this opportunity of correcting that omission.