The origin of cherry eye-color (Plate II, fig. 9) has been given by Safir (Biol. Bull., 1913). From considerations which will be discussed later in this paper we regard cherry as allelomorphic to white in a quadruple allelomorph system composed of white, eosin, cherry, and their normal red allelomorph. Cherry will then occupy the same locus as white, which is one unit to the right of yellow, and will show the same linkage relations to other factors as does white. A slightly lower cross-over value should be given by cherry and sable than was given by yellow and sable. When cherry (gray) females were crossed to (red) sable males the daughters were wild type and the sons cherry. Inbred these gave the results shown in table 10. TABLE 10.--_P_1 cherry [female][female] x sable [male][male]. F_1 wild-type [female] x F_1 cherry [male] [male]._ +---------+---------+---------+--------------+------------+------+------+ | | | | Non-cross- | Cross-over | | | | | Wild- | Cherry | over [male]. | [male]. | |Cross-| | Refer- | type |[female].+-------+------+------+-----+Total | over | | ence. |[female].| |Cherry.|Sable.|Cherry|Wild-|males.|value.| | | | | | |sable.|type.| | | +---------+---------+---------+-------+------+------+-----+------+------+ | | | | | | | | | | | 24 I | 94 | 105 | 51 | 42 | 20 | 43 | 156 | 40 | | 55 I | 101 | 131 | 63 | 52 | 38 | 48 | 201 | 43 | | 55' I | 96 | 94 | 52 | 31 | 29 | 30 | 142 | 42 | | +---------+---------+-------+------+------+-----+------+------+ | Total | 291 | 330 | 166 | 125 | 87 | 121 | 499 | 42 | | | | | | | | | | | +---------+---------+---------+-------+------+------+-----+------+------+ The percentage of crossing-over between cherry and sable is 42. Since cherry is one point from yellow, this result agrees extremely well with the value 43 for yellow and sable. Since yellow and eosin lie at the left end of the first chromosome, the high values, namely, 43 and 42, agree in making it very probable that sable lies near the other end (_i. e._, to the right). Sable will lie farther to the right than vermilion, for vermilion has been shown elsewhere to give 33 per cent of crossing-over with eosin. The location of sable to the right of vermilion has in fact been substantiated by all later work. LINKAGE OF EOSIN, VERMILION, AND SABLE.