Head activator does not qualitatively alter head morphology in regenerates ofHydra oligactis.

The characterization of head activator (HA) as a morphogen capable of increasing the number of tentacles regenerated by hydra was re-examined. Gastric tissue was excised from HA-treated whole animals and allowed to regenerate. At the cellular level the differentiation of head-specific ectodermal epithelial cells was monitored by quantifying monoclonal antibody, CP8, labeling.