Brachet ('50~) has accumulated a great amount of evidence which implicates ribonucleic acid or ribonucleoprotein as the inductive substance which initiates differentiation of the presumptive neural tissue in the amphibian embryo. Niu and Twitty ('53) have found that the diffusible medium collected from cultures of dorsal-axial tissues, which elicits the differentiation of neurons, chromatophores o r myoblasts from cultured ectodermal cells, contains nucleoprotein as seen by its inactivation with ribonuclease and proteolytic enzymes and its absorption in the ultra-violet. If ribonucleoprotein is essential for determination of the reacting tissue, it would be of interest to know the constitution of the inducing and reacting tissues with regard to these substances. The purpose of this research is to determine the levels of RXA and protein in various centrifugal fractions in the inducing and reacting tissues throughout induction of the neural plate of the frog embryo and to observe the factors which affect changes in the RNA and protein content of these tissues.
Methods
Analysis of tissue layers. Raiza pipiems gastrulae and neurulae (stages 10 through 15, Shumway, '40) were selected Submitted as a thesis in partial satisfaction of the requirements for the degree