There is a case comparable to this found in a wild species of moth, Abraxas grossulariata. A wild variation of this type is lighter in color and is known as A. lacticolor. When these two types are crossed they exhibit exactly the same type of heredity as does the black-barred combination in the domestic fowl. As shown in figure 41, lacticolor female bred to grossulariata male gives grossulariata sons and daughters. These inbred give grossulariata males and females and lacticolor females. Reciprocally lacticolor male by grossulariata female, (fig. 42) gives lacticolor daughters and grossulariata sons and these inbred give grossulariata males and females and lacticolor males and females. [Illustration: FIG. 41. Sex-linked inheritance in the wild moth, Abraxas grossulariata (darker) and A. lacticolor.] [Illustration: FIG. 42. Reciprocal of Fig. 41.] [Illustration: FIG. 43. Four wild types of Paratettix in upper line with three hybrids below.] It has been found that there may be even more than two factors that show Mendelian segregation when brought together in pairs. For example, in the southern States there are several races of the grouse locust (Paratettix) that differ from each other markedly in color patterns (fig. 43). When any two individuals of these races are crossed they give, as Nabours has shown, in F_2 a Mendelian ratio of 1: 2: 1. It is obvious, therefore, that there are here at least nine characters, any two of which behave as a Mendelian pair. These races have arisen in nature and differ definitely and strikingly from each other, yet any two differ by only one factor difference. [Illustration: FIG. 44. Diagram illustrating four allelomorphs in mice, viz. gray bellied gray (wild type) (above, to left); white bellied gray (above, to right); yellow (below, to right); and black (below, to left).] Similar relations have been found in a number of domesticated races. In mice there is a quadruple system represented by the gray house mouse, the white bellied, the yellow and the black mouse (fig. 44). In rabbits there is probably a triple system, that includes the albino, the Himalayan, and the black races. In the silkworm moth there have been described four types of larvae, distinguished by different color markings, that form a system of quadruple allelomorphs. In Drosophila there is a quintuple system of factors in the sex chromosome represented by eye colors, a triple system of body colors, and a triple system of factors for eye colors in the third chromosome. MUTATION AND EVOLUTION