AbstractThe process of vitellogenesis in oviparous vertebrates embraces a number of integrated physiological and developmental phenomena. Since this process is readily subjected to experimental control inXenopus laevis, we have been able to undertake a preliminary survey of the pertinent mechanisms operating in this animal.The information at hand is discussed as it relates to (a) the hormonal (estrogen) induction of yolk protein synthesis by the liver, (b) the characterization of the yolk protein produced and its relationship to the proteins of the mature egg, (c) the transport of the yolk protein to the ovary and its specific uptake by the developing oocyte, and (d) the transformation of the accumulated protein into crystalline yolk platelets.