Abstract
Summary.: The posterior lobe contains no metamorphic principle. Injection of extracts of the posterior lobe pituitary inhibit the metamorphosis of normal frog tadpoles. Injection of extracts of the posterior lobe pituitary retard the accelerated metamorphosis produced by iodine solution, but the effect decreases with increased concentration of iodine. Injections of extracts of posterior lobe inhibit accelerated metamorphosis induced by thyroid or anterior pituitary extracts, the effectiveness depending on quantities administered.