330 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1948 
Watts, G. L., and Jupp, H. D. Woop, C. A. 
1933. The intra-ocular colour filters of 1917. The fundus oculi of birds. Chi- 
vertebrates. Brit. Ophthalmol., cago. 
vol. 17, pp. 641-675, 705-725. YEAGLEy, H. L. 
Watson, J. B. 1947. A preliminary study of a physical 
1915. Studies on the spectral sensitivity basis of bird navigation. Journ. 
of birds. Pap. Dep. Marine Appl. Phys., vol. 18, pp. 1035— 
Biol., Carnegie Inst. Washing- 1063. 
ton, vol. 7, pp. 87-104. 
