Table 27.—Summary of all data upon lethal 2, from Morgan, 1914b.
| Gens. | Total. | Cross-overs. | Cross-over values. |
| White lethal 2 | 8,011 | 767 | 9.6 |
| White vermilion | 6,023 | 1,612 | 26.8 |
| White miniature | 36,021 | 11,048 | 30.7 |
| Lethal 2 vermilion | 1,400 | 248 | 17.7 |
| Lethal 2 miniature | 6,752 | 1,054 | 15.4 |
The amount of crossing-over between eosin and lethal is about 10 per cent and the amount of crossing-over between lethal and miniature is about 18 per cent. Since the amount of crossing-over between eosin
and miniature is over 30 per cent, the lethal factor must lie between eosin and miniature, somewhat nearer to eosin. It is impossible at present to locate lethal 2 accurately because of a real discrepancy in the data, which makes it appear that lethal 2 extends for a distance of about 5 units along the chromosome from about 10 to about 15. Work is being done which it is hoped will make clear the reason for this. For the present we may locate lethal 2 at the midpoint of its range, or at 12.5.
CHERRY.
([Plate II], figure 9.)
The origin of the eye-color cherry has been given by Safir (Biol. Bull., 1913).
Cherry appeared (October 1912) in an experiment involving vermilion eye-color and miniature wings. This is the only time the mutant has ever come up, and although several of this mutant (males) appeared in Safir's experiment, they may have all come from the same mother. It is probable that the mutation occurred in the vermilion stock only a generation or so before the experiment was made, for otherwise cherry would be expected to be found also in the vermilion stock from which the mothers were taken; however, it was not found.
A SYSTEM OF QUADRUPLE ALLELOMORPHS.
Safir has described crosses between this eye-color and red, white, eosin, and vermilion. We conclude for reasons similar to those given by Morgan and Bridges (Jour. Exp. Zool., 1913) for the case of white and eosin, that cherry is an allelomorph of white and of eosin. This is not the interpretation followed in Safir's paper, where cherry is treated as though absolutely linked to white or to eosin. Both interpretations give, however, the same numerical result for each cross considered by itself. Safir's data and those which appear in this paper show that white, eosin, cherry, and a normal (red) allelomorph form a system of quadruple allelomorphs. If this interpretation is correct, then the linkage relations of cherry should be identical with those of white or of eosin.