| First generation. | Second generation. | |||||||||||
| Reference. | Wild- type ♀. | Ver- milion ♂. | Reference. | Wild- type ♂. | Wild- type ♀. | Ver- milion ♂. | Ver- milion ♀. | Ver- milion dot ♂. | Ver- milion dot ♀. | Dot ♂. | Dot ♀. | |
| 137 C. | 44 | 45 | 19 | 211 | 198 | 228 | 206 | 20 | 3 | 0 | 0 | |
| 138 C. | 77 | 62 | 22 | 266 | 220 | 227 | 227 | 16 | 0 | 0 | 0 | |
| 124 | 124 | 28 | 143 | 149 | 125 | 124 | 14 | 1 | 0 | 0 | ||
| 57 | 41 | Total. | 620 | 567 | 570 | 557 | 50 | 4 | 0 | 0 | ||
| Total. | 291 | 272 | ||||||||||
The F2 generation is given in table 20. The dot reappeared in F2 both in females and in males, but instead of appearing in 50 per cent of both sexes, as expected if it is simply sex-linked, it appeared in 4.0 per cent in the females and in only 0.4 per cent in the males. The failure of the character to be fully realized is again apparent, but here, where it is possible for it to be realized equally in males and females, we find that there are 50 females with dot to only 4 dot males. This would indicate that the character is partially "sex-limited" (Morgan, 1914d) in its realization. The dot appeared only in flies with vermilion eyes, indicating extremely strong linkage between vermilion and dot.
The evidence from the history of the stock, together with these experiments, shows that the character resembles club (wing) in that it is not expressed somatically in all the flies which are homozygous for it. In the case of club we were fortunate enough to find a constant feature
which we could use as an index, but, so far as we have been able to see, there is no such constant accessory character in the case of the dot. Unlike club, dot is markedly sex-limited in its effect; that is, there is a difference of expression of the gen in the male and female. This difference recalls the sexual dimorphism of the eosin eye.
BOW.
In an F2 generation from rudimentary males by wild females there appeared, August 15, 1912, a single male whose wings instead of being flat were turned down over the abdomen (fig. c). The curvature was uniform throughout the length of the wing. A previous mutation, arc, of this same type had been found to be a recessive character in the second group. The new mutation, bow, is less extreme than arc and is more variable in the amount of curvature. When the bow male was mated to wild females the offspring had straight wings.
Table 21.—P1 bow ♂♂ × wild ♀♀.
| First generation. | Second generation. | ||||||
| Reference. | Wild-type ♀♀. | Wild-type | Reference. | Wild-type ♀♀. | Wild-type ♂♂. | Bow ♂♂. | |
| 169 C. | 17 | 17 | 18 I. | 193 | 145 | 67 | |
| 21 I | 182 | 100 | 49 | ||||
| Total. | 375 | 245 | 116 | ||||