CELL PROLIFERATION IN HYDRA: AN AUTORADIOGRAPHIC APPROACH.

Hydra cells take up substantial amounts of tritiated thymidine if the label is injected into an animal's gastric cavity shortly after feeding. Autoradiographic analysis shows that the isotope becomes incorporated into cell nuclei. The distribution of labeled nuclei probably represents the pattern of cell proliferation and is similar to the distribution of mitotic figures in histological preparations. The data show that cell proliferation is distributed along the body column and that there is no localized growth zone.