1. Brown, D. D., and Littna, E., J. Mol. Biol., 8, 669 (1964).
2. Shiokawa, K., and Yamana, K., Exp. Cell Res., 38, 180 (1965).
3. Cohen, S., J. Biol. Chem., 211, 337 (1954).
4. Stearns, R. N., and Kostellow, A. B., in The Chemical Basis of Development (edit. by McElroy, W. D., and Glass, B.), 448 (Johns Hopkins Univ. Press, Baltimore, 1958).
5. Nieuwkoop, P. D., and Faber, J., Normal Table of Xenopus laevis (Daudin) (North-Holland Pub. Co., Amsterdam, 1956).