Localization of Formative Agencies in Hydra

Abstract

In H. oligactis, as Browne had demonstrated in H. viridis, peristomal tissue induces hydranth-formation at the place it is grafted upon the "stock" of a 2nd polyp. If a new "head" be thus induced to form near the original one and the latter be cut off, there will be no regeneration of a head in the majority of cases. The new head will eventually be shifted into the polar axis of the polyp. Space relations between grafted tissues and those of the stock were shown to constitute a factor in determining the experimental results. It is concluded that peristomal tissue may exercise, under certain conditions, a positive dominance and determine head formation; while, under other conditions, peristomal tissue may exercise a negative dominance and inhibit head formation. The authors recognize that their data "are in need of corroboration and extension," data for which are to appear in future papers.