1. Bittner, J. J., Nat. Bull. No. 2, Roscoe B. Jackson Memorial Lab., 3 (1936).
2. Biggers, J. D., Finn, C. A., and McLaren, A., J. Reprod. Fert. (in the press).
3. Perry, J., Embryol. Exp. Morph., 2, 308 (1954).
4. Jones, E. C., and Krohn, P. L., J. Endocrinol., 21, 469 (1961).