Table 4.—Summary of linkage data upon reduplicated legs, from Hoge, 1915.
| Gens. | Total. | Cross- overs. | Cross-over values. |
| White reduplicated | 418 | 121 | 29.0 |
| Reduplicated vermilion | 667 | 11 | 1.7 |
| Reduplicated bar | 583 | 120 | 20.6 |
The most accurate data, those upon the value for reduplicated and vermilion, give for reduplicated a distance of 1.7 from vermilion, either to the right or to the left. The distance from white is 29, which would place the locus for reduplication to the left of vermilion, which is at 33. The data for bar give a distance of 21, but since bar is itself 24 units from vermilion, this distance of 21 would seem to place the locus to the right of vermilion. The evidence is slightly in favor of this position to the right of vermilion at 34.7, where reduplicated may be located provisionally. In any case the locus is so near to that of vermilion that final decision must come from data involving double crossing-over, i. e., from a three-locus experiment.
LETHAL 1.
In February 1912 Miss E. Rawls found that certain females from a wild stock were giving only about half as many sons as daughters. Tests continuing through five generations showed that the sons that appeared were entirely normal, but that half of the daughters gave again 2 : 1 sex-ratios, while the other half gave normal 1 : 1 sex-ratios.
The explanation of this mode of transmission became clear when it was found that the cause of the death of half of the males was a particular factor that had as definite a locus in the X chromosome as have other sex-linked factors (Morgan, 1912e). Morgan mated females (from the stock sent to him by Miss Rawls) to white-eyed males. Half of the females, as expected, gave 2 : 1 sex-ratios, and daughters from these were again mated to white males. Here once more half of the daughters gave 2 : 1 sex-ratios, but in such cases the sons were nearly all white-eyed and only rarely a red-eyed son appeared, when under ordinary circumstances there should be just as many red sons as white sons. The total output for 11 such females was as follows (Morgan, 1914b): white ♀, 457; red ♀, 433; white ♂, 370; red ♂, 2. It is evident from these data that there must be present in the sex-chromosome a gen that causes the death of every male that receives this chromosome, and that this lethal factor lies very close to the factor for white eyes. The linkage of this lethal (now called lethal 1) to various other sex-linked gens was determined (Morgan 1914b), and is summarized in table 5. On the basis of these data it is found that the gen lethal 1 lies 0.4 unit to the left of white, or at 0.7.
Table 5.—Summary of linkage data upon lethal 1, from Morgan, 1914b, pp. 81-92.
| Gens. | Total. | Cross- overs. | Cross-over values. |
| Yellow lethal 1 | 131 | 1 | 0.8 |
| Yellow miniature | 131 | 45 | 34.4 |
| Lethal 1 white | 1,763 | 7 | 0.4 |
| Lethal 1 miniature | 814 | 323 | 39.7 |
| White miniature | 994 | 397 | 39.9 |
LETHAL 1a.