A histological study of irradiated thyroid and pituitary glands of metamorphosing Xenopus tadpoles was made. Both glands shrink, reaching a minimum nine hours after irradiation and recover by 24 hours. It is suggested that sudden release of hormones may explain a reported hastening of metamorphosis in irradiated tadpoles.
Xenopus larvae received 2500 rads of whole body X-rays.
Nine hours after irradiation both pituitary and thyroid volumes were significantly less than the controls. From 24 hours after, the volumes had returned to control levels.
The mitotic incidence in irradiated thyroids fell within five hours to one tenth of the control value and remained suppressed for at least three days.