336 Morgan. 



Additional crosses between Miniature and Rudimentary. 



As stated, a large number of crosses were carried out during the 

 winter of 1910 — 11, when the unexpected sex ratio in F2 long-wmged 

 flies was first observed but not understood. A few of these may now 

 be cited: (i) Miniature 9 mated to Rudimentary ö gave: 



9 long 9 and 3 min. ß 



These inbred gave: 



L 9 128 L (5 18 Min. 9 61 Win. cj 71 Rud. (and Rud.-min.) (J 13 



Some of the long winged 9 (not necessarily virgin) were mated to 

 some of the Min. Ö and gave: 



L 9 131 L (5 19 Min. 9 57 Min. (5 62 



Other of the long winged 9 (not necessarily virgin) were mated to 

 the Rud. d and gave: 



L 9 50 L (J 5 Min. (5 7 Rud. (5 2 



(2) Miniature 9 mated to Rud. ö gave long-winged 9 . These long- 

 winged females were mated to males, found in the same bottle, which 

 were presumably the fathers of the "long" females; in other words 

 a back cross resulted, which gave: 



L 9 127 L (^ 20 Min. (5 43 Kud. 9 4 Rud. cJ 2 



The expectation is as follows: 



rMX — rMX = Min. 9 

 RmX — rm = Rud. cj 



Fj 9 rMX — RmX = Long 9 



Gametes of F, 9 . . RMX — rMX — RmX — rmX 

 Rud. (5 RmX — rm 



The effects of linkage on the sex-ratio. 



In an earlier, preliminary note^), a remarkable relation in the 

 sex-ratios of long-wing flies in certain crosses was recorded. At that 



1) Proceed. Soc. Exp. Biol, and l\Ied. 191 1. 



