When this mutant first appeared its similarity to arc led us to suspect that it might be arc itself or an allelomorph of arc. It was bred, therefore, to arc. The bow male by arc females gave straight (normal) winged males and females. The appearance of straight wings shows that bow is not arc nor allelomorphic to arc. When made later, the reciprocal cross of bow female by arc male gave in F_1 straight-winged females but bow males. This result is in accordance with the interpretation that bow is a sex-linked recessive. Further details of these last two experiments may now be given. The F_1 (wild-type) flies from bow male by arc female were inbred. The data are given in table 22. TABLE 22.--_P_1 bow [male] x arc [female]._ +--------------------------------------------+ | First generation. | +----------+------------------+--------------+ |Reference.| Wild-type | Wild-type ~ | |[female] [female].|[male] [male].~ +----------+------------------+--------------+ | 71 C. | 48 | 43 | | 75 C. | 28 | 27 | | +------------------+--------------+ | Total.| 76 | 70 | +----------+------------------+--------------+ +------------------------------+ | Second generation. | +----------+---------+---------+ ~Reference.|Straight.| Not- | ~ | |straight.| +----------+---------+---------+ | 71 C. | 179 | 133 | +----------+---------+---------+ Bow and arc are so much alike that they give a single rather variable phenotypic class in F_2. Therefore the F_2 generation is made up of only two separable classes--flies with straight wings and flies with not-straight wings. The ratio of the two should be theoretically 9:7, which is approximately realized in 179:133. If the distribution of the characters according to sex is ignored, the case is similar to the case of the two white races of sweet peas, which bred together gave wild-type or purple peas in F_1 and in F_2 gave 9 colored to 7 white. If sex is taken into account, the theoretical expectation for the F_2 females is 6 straight to 2 arc, and for the F_2 males 3 straight to 1 arc to 3 bow to 1 bow-arc. The F_1 from bow females by arc male and their F_2 offspring are given in table 23. {48} TABLE 23.--_P_1 bow [female] x arc [male]._