ABSTRACT
The existence of a physiological gradient in Hydra has been repeatedly demonstrated by a number of investigators, and the hypostome, which is supposed to be the region of highest metabolic activity, has generally been regarded as the organization centre of the animal. Earlier transplantation experiments (Browne, 1909; Rand, Bovard and Minnich, 1926; Mutz, 1930) indicated that when a piece of hypostome is grafted, it can act as an organizer and induce a new hydranth. Although these are all well-known facts, the underlying mechanism in the induction process remains obscure. The present work is the first step in an attempted physiological analysis of the problem, with special reference to the induction potency of implants derived from different body levels, and to the nature of the induced hydranth.
