Abstract IN STUDIES on the inheritance of egg eight, Benjamin (1920) in White Leghorns, Waters and Weldin (1929) in White Plymouth Rocks, Hurst (1921) in White Leghorns and White Plymouth Rocks and Kopec (1924) in crosses between Leghorn males and Polish Greenfoot females used, as a genetic measure, mean or modal annual egg weight. The conclusions drawn from these studies did not agree. Benjamin, Hurst, and Kopec found evidence for the dominance of small egg size, while Waters and Weldin concluded that large egg size was dominant. Hays (1929), in Rhode Island Reds, used the mean weight of eggs laid from commencement of laying to the first of January of the pullet laying year as a genetic measure. Hays concluded that egg weight must depend upon several heritable factors and proposed a theory involving a pair of autosomal genes, BB, dominant for large egg size, and a pair of autosomal genes . . .