The Acquisition, Maintenance, and Lability of the Differentiated State in Hydra

Abstract

The title of this collection of papers, “The Stability of the Differentiated State”, implies that the organisms discussed herein contain differentiated cells. However, one of the central questions we shall be discussing throughout the text is: does differentiation signify a fixed, irreversible state of a cell? For me, using Hydra as an experimental model, to accept the definition that a differentiated cell cannot dedifferentiate would be tantamount to saying that the animal probably contains no differentiated cells. If this is true then none of the material presented here will be relevant to a discussion of differentiation. There is one thing to be said, however, for the foregoing definition — it is a clear formulation and not subject to semantic bickering. All other definitions of differentiation are fraught with exceptions and lead invariably to long, often tedious hours of endless debate that leave symposium participants with ragged nerves, bad digestion and an urge to get back into the laboratory and get to work because the discussion accomplished nothing.