Rh Genes Allelomorphic to C

THE third allelomorph, C^w, at the C-c locus of the Rh chromosome was not recognized until a pure anti-C^w serum was found¹; but its existence could have been demonstrated by testing several hundred samples of blood with a range of anti-C sera, for some of these sera are of the specificity anti-C and some, the majority, anti-C + C^w. It is not yet clear why the latter type of antibody may result from stimulation by the antigen C.