Hydranths of the colonial marine hydroid Campanularia flexuosa (phylum Cnidaria, class Hydrozoa, order Calyptoblastea) have a mean life span of approximately 7 days in intact colonies in culture. Hydranths then regress and are absorbed, and their cellular materials are utilized by the colony for continued growth. Hydranth life spans can be extended to 20 days in isolated hydranths if, repeatedly, the pedicel is damaged by pinching and is allowed to partially regen-erate. This suggests that tissue damage and reorganization function to maintain the hydranth.