By combining the results of tables 41 and 42 data are obtained for cross-over values from which (by balancing the inviable classes, as explained in table 43) the element of inviability is reduced to a minimum. TABLE 43. +----------+------------+------------+------------+------------+--------+ | | | | | | | | | ------ | -+---- | ----+- | -+--+- | Total. | | | | | | | | +----------+------------+------------+------------+------------+--------+ | | | | | | | | | 1,164 | 5 | 32 | 0 | 1,201 | |Per cent. | 96.9 | 0.42 | 2.7 | 0 | | +----------+------------+------------+------------+------------+--------+ The linkages involved in these data are very strong. The cross-overs between forked and bar number only 5 in a total of 1,201, which gives less than 0.5 per cent of crossing-over. There are 32 cross-overs or 2.7 per cent between bar and fused. The value for forked fused is the sum of the two other values, or 3.1 per cent. LINKAGE OF SABLE, RUDIMENTARY, AND FORKED. Rudimentary, forked, bar, and fused form a rather compact group at the right end of the chromosome, as do yellow, lethal 1, white, abnormal, etc., at the zero end. The following two experiments were made to determine more accurately the interval between rudimentary and the other members of this group. A sable rudimentary forked {61} male mated to a wild female gave wild-type sons and daughters. These inbred give the results shown in table 44. TABLE 44.--_P_{1} sable rudimentary forked_ [male] x _wild_ [female]. _F_{1} wild-type_ [female] x _F_{1} wild-type_ [male] [male]. +----------+---------+-----------------+-------------------+ | | | s r f | s | | | | ------ | -+---- | | | | | r f | | | +-----------+-----+-------+-----------+ |Reference.|Wild-type| Sable |Wild-| Sable.|Rudimentary| | |[female] |rudimentary|type.| | forked. | | |[female].| forked. | | | | +----------+---------+-----------+-----+-------+-----------+ | 264 | 98 | 28 | 17 | 2 | 5 ~ | 265 | 97 | 29 | 54 | 4 | 9 ~ | 266 | 114 | 42 | 49 | 11 | 11 | +----------+---------+-----------+-----+-------+-----------+ |Total | 309 | 99 |120 | 17 | 25 | +----------+---------+-----------+-----+-------+-----------+