A Modification of the Sex Ratiu, and of other Ratios, etc. 32Q 



(RmXRmX Rudimentary 9 

 RmXRMX Long $ 

 iRmXrm Rudimentary (5 

 R:MXrm Long (J 



The preceding cases give the results of crosses between the mutants 

 and the normal or wild flies. The relation of the mutants to each 

 other, and the relation of a new type or permutant, (that appears 

 in the second generation of the next crosses,) to the long winged 

 type will be considered in the following experiments. 



When a rudimentary winged male is crossed to a miniature 

 winged female all the females have long wings and all the males 

 have miniature wings. These inbred give the following results: 



Long 2 2216 



Rud. dbyMin. 9 = ^°°^!^'^ 

 Mm. cJ 574 



., <J 401 

 Miniature 9 1969 

 c5 1617 

 Rudimentary (J 781 

 Rudimentary-miniature (J 



There are certain extraordinary departures from Mendelian ratios 

 in this last case as a comparison with the expectation that follows 

 will show. For instance, the long winged males run far behind the 

 miniature males in actual numbers, although the expectation calls for 

 equality. Likewise, the new class called Rudimentary-miniature Fig. 2 

 numbers only 184 males while expectation calls for as many as for 

 miniature males, viz., 1617. It will be shown later that these results 

 are due largely to linkage; for present purposes little more than the 

 realization of the expected classes need be considered. But at least 

 it should be noted (see gametes of F^ below) that the large classes of 

 normal females, miniature females and males, and rudimentary males, 

 come from those combinations (linkages) that existed in the grand- 

 parents, while the small classes of long winged males and rudi- 

 mentary-miniature males are due to interchange ("crossing-over") of 

 these factors. In the following and in all subsequent analyses, in 

 which "crossing-over" takes place, the original linkages are given in 

 the two middle terms of the egg-gametes, while the two outer terms 

 (that give the small classes) represent the interchanges, or the break 

 in the linkages. 



The analysis of the preceding case follows: 



Miniature 9 rMX — rMX 



Rudimentary c5 • . • RmX — rm 



