Abstract
The species-specific antigens A, B, C, E, and F of the erythrocytes of C. guinea in contrast to C. livia appear in embryos and squabs from matings of backcross hybrids with C. livia and from matings of the backcross hybrids inter se by 72 hours of incubation, or approx. the 29-somite stage, which is as early as enough blood can be obtained for testing. Antigens A and F tend to be weak or "absent" after hatching of the squab and during the first 2 months thereafter.