The changes which occur in the body-weight of frogs, axolotls, and aquatic reptiles as a result of the injection of vasopressin are generally ascribed to changes in body-water [e.g. Brunn, 1921; Bělehrádek and Huxley, 1927; Heller, 1930; Steggerda, 1931; Steggerda and Essex, 1934; Rey, 1935; Steggerda, 1937; Boyd and Brown, 1938; Boyd and Whyte, 1938; and Boyd and Dingwall, 1939]. The mechanism of the change appears to differ somewhat in different species, but in amphibia it appears to be due both to the increased absorption of water through the skin [Steggerda, 1931] and to antidiuresis [e.g. Rey, 1935; Pasqualini, 1938], with the consequent storage of excess water in muscle, subcutaneous, and other tissues [Steggerda and Essex, 1934; Boyd and Brown, 1938]. In view of the simplicity of the technique necessary to follow gross changes in body-water in these animals, it was of interest to inquire whether or not sex hormones