The Differential Action of X-rays on the Anterior and Posterior Regions ofTubifex Tubifex

Abstract

IT IS well known that posterior regeneration in Tubifex tubifex occurs when it is separated with a knife at any level behind the tenth somite and that, following x-ray irradiation, regeneration is inhibited (Stone, 1932). In this paper experiments are described in which the separation was accomplished by irradiating several somites with an intense collimated beam of soft x-rays, and also some experiments in which irradiation of all the animal caused the death of only the posterior. Methods.—Mud containing the animals was collected at frequent intervals for a period of over a year along the shore of Burnet Woods Lake, near the University, and kept in porcelain pans at room temperature in the laboratory. The animals were removed from the mud just before they were irradiated. After irradiation they were kept in clear water in small Petri dishes or in the depressions of well slides. The work may be conveniently divided into two parts, of which the first is concerned with the irradiation of a very small part o...