Abstract
Quantitative assays for the first appearance of the hormone, intermedin, in larvae of R. pipiens were made, using the hypophysectomized lizard, Anolis carolinensis, as test ani mal. Intermedin is detectable with the establishment of the hypophyseal primordium as an invagination from the buccal ectoderm. The gland in larvae 4-7 mm. in length contains approx. 0.3 Anolis unit of intermedin which appears be fore cytological differentiation of the pituitary gland occurs.