THE MITOTIC RATE IN TADPOLE SKIN AFTER REPEATED INJURY

¹ From the Department of Zoölogy, University of Missouri, and from the Marine Biological Laboratory, Woods Hole, Mass.

Successive half-centimeter pieces were cut each day for eight days from the tails of bullfrog tadpoles. The epidermis maintained a very low rate of epidermal mitosis despite the great loss of cells by migration over the injured surfaces. Conspicuous exceptions with relatively high rates were found in cases where the epidermis failed to cover the seventh or eighth wound within twenty-four hours after injury. Here the mitotic rate reached a value twenty times the previous average rate.