Within the last decade, statistical evidence has accumulated that the ABO blood groups have selective influences other than those due to mis matched or unavailable transfusions, and an in creasing literature has convincingly demonstrated a primary influence on at least one group of diseases in adults. Publications on the influence of the ABO phenotypes on fertility and sex ratio have made similar claims of apparent selective influences inex plicable by chance, and such claims have been widely quoted {British Medical Journal, 1954), and have been promoted to the attention of geneticists in the Bateson lecture on morphism (Huxley, 1955).