ABSTRACT LINDSTROM et al. (1949) and Olcese, Couch and Lyman (1950) showed that the addition of vitamin B12 supplements produced by fermentation to all-vegetable protein diets improved the hatchability of eggs of hens fed these diets. Lillie, Olsen and Bird (1949), and Olcese and Couch (1950) improved hatchability by injecting crystalline vitamin B12 into eggs laid by hens fed diets deficient in this vitamin. Petersen et al. (1950), and Peeler et al. (1951) found that the hatchability of eggs laid by hens depleted of their vitamin B12 reserves was markedly increased when the hens received intramuscular injections of vitamin B12. Yacowitz and associates (1952) observed that White Leghorn pullets were depleted of their vitamin B12 reserves more rapidly when fed a diet containing 25 percent protein than when the diet contained 16 percent protein. The vitamin B12 requirement for normal hatchability of White Leghorn hens fed the high protein diet was . . .