Cell Division during Regeneration in Hydra

PROCESSES considered to be involved in regeneration in Hydra include tissue displacement, cell migration, cell proliferation and cell differentiation1. The relative importance of these processes is not clearly understood. Several people have reported that cell proliferation plays only a minor part2, but no quantitative study of cell division in regenerating hydras has been published. We have compared the mitotic index during regeneration of a new hypostome and tentacles (Fig. 1) with the mitotic index in intact hydras, and report here that cell division is not important in regeneration.