Activity of Hydra Cells in vitro and in Regenerating Cell Reaggregates

Hydra were disaggregated into single cells and maintained ina complex medium for a few days. The cells are capable of macromolecularsynthesis, of processing RNA, and of carrying out the formationof a nematocyst capsule. Single cells can be centrifuged intoaggregates which will develop into normal hydra. Changes inmorphology and cell composition are described. Interstitialcells after a 1-day delay resume their normal mitotic and differentiationactivity in the aggregates. The method provides new means forstudying problems of cell differentiation in hydra.