Our objective is to determine how endocrine gland secretions affect the morphological and biochemical differentiation of the rhesus fetus and placenta. These studies will be carried out on experimental groups of fetuses of known conceptual age which 1) have been functionally hypophysectomized, 2) have no CNS stimulus to an intact hypothalamic-pituitary axis, and 3) have intact pituitaries but no stimuli from the hypothalamus. The chronic effect of these endocrine lesions on organogenesis, cytology, and biochemical differentiation in various tissues will be observed. Appropriate methods will be used to assay enzyme levels in liver, kidney, and other tissues. Plasma levels of pituitary and steroid hormones will be monitored by radioimmunoassay.