1. McLeish, J., Heredity, 8, 385 (1954).
2. Gaulden, M. B., and Perry, B. P., Proc. U.S. Nat. Acad. Sci. (in the press)
3. Lindsley, D. L., and Novitski, E., Genetics (in the press).
4. Poulson, D. F., J. Exp. Zool., 83, 271 (1940).
5. von Borstel, R. C., in “The Beginnings of Embryonic Development”, 175, edit. by Tyler, A., von Borstel, B. C., and Metz, C. B. (A.A.A.S., Washington, B.C., 1957).