1. Juhn, M., and Gustavson, R. G., J. Exp. Zool., 56, 31 (1930).
2. Wang, H., J. Exp. Zool., 109, 451 (1948).
3. Caridroit, F., and Regnier, V., Sixth World's Poultry Cong., Section 3, 12 (1936).
4. Trinkaus, J. P., Proc. Third Conf. Biology of Normal and Atypical Pigment Cell Growth, 73 (Academic Press, New York, 1953).
5. Juhn, M., Faulkner, G. H., and Gustavson, R. G., J. Exp. Zool., 58, 69 (1931).