Among the so-called japanese breeds of mice “Nahkin” and “Kasuri” (wal'zer), the pink-eyed variety is very common. This eye color behaves recessive to the dark eye. The writers obtained incidentally a ruby-eyed mouce fnom an animal dealer. Using this new type in breeding experiments, it proved to be allelomorphic to both pink and dark eyes. In other words, these eye colors may constitute a triple-allelomorph, the order of dominancy being dark. ruby and pink eyes.