SOME time ago Prof. Wallace, of the School of Mines, Kimberley, suggested to me the possible explanation of the difference in colour of the light reflected from the iris of the eyes of different people—that it was in accordance with the natural law of protection against external influences. He pointed out that people hailing from regions where blue light is predominant—Swedes, Norwegians, and sailors, for instance—have blue eyes, whilst near the equator, or in sandy climes such as South Africa, where intense yellow light is experienced, the eyes take a rich dark yellow hue, as those of the Kaffirs and Malays, Italians and Spaniards. The Scotch have blue, the English grey, and the French dark eyes, generally speaking.