Abstract
While the precipitin tests do not differentiate, according to the results of previous workers, between the serum proteins of man and chimpanzee, a clear-cut differentiation between the blood cells of man and the anthropoids was obtained by means of hemagglutinins. According to our tests on bloods of whites and negroes, constant racial serological differences among human bloods, if they exist at all, are certainly smaller than the differences between the bloods of man and the anthropoid apes. The serological differences between man and the lower monkeys appear to be no greater than those between the anthropoid apes and the lower monkeys. These findings confirm the opinion that the anthropoid apes do not rank in the genealogical tree between lower monkeys and man.