1. Bagnara, J.T., Taylor, J.D., Hadley, M.E.: The dermal chromatophore unit. J. Cell Biol.38, 67?79 (1968)
2. Barth, L.G., Barth, L.J.: Differentiation of cells of theRana pipiens gastrula in unconditioned medium. J. Embryol. Exp. Morphol.7, 210?222 (1959)
3. Chen, P.S.: Metabolic changes in free amino acids and peptides during urodele development. Exp. Cell Res.10, 675?686 (1956)
4. Deuchar, E.M.: Amino acids in developing tissues ofXenopus laevis. J. Embryol. Exp. Morphol.4, 327?346 (1956)
5. Landström, U.: On the differentiation of prospective ectoderm to a ciliated cell pattern in embryos ofAmbystoma mexicanum. J. Embryol. Exp. Morphol.41, 23?32 (1977)