In conformity with the results of Landsteiner and Miller (1924) the experiments here reported do not disclose any racial differences in the factors concerned with hemagglutination; the same factors are apparently found in the various breeds but differently assorted in the various individuals.
There is evidence that the number of factors underlying the reaction with a hetero-agglutinating serum is rather small; the individual variation might well be accounted for by a variable assortment of a small number of factors.
Inbred strains show a relatively high degree of homogeneity in their agglutinogens as compared with unrelated birds. This undoubtedly is due to the Mendelian transmission of the factors that are responsible for the formation of specific agglutinogens.
This work was carried out at the University of Chicago during the writer's tenure of a National Research Council Fellowship. The expenses of this investigation were borne in part by the Committee for Research in Problems of Sex of the National Research Council and the University of Chicago.