LINKAGE OF THE FACTOR FOR BIFID WING. 159 



The number of crossovers is far too small to give the same ratio 

 found in Experiment VI. Here the percentage is only 4. 



EXPERIMENT VIII. 



This is a modification of Experiment VI. LR females were 

 mated with BfW males. The F 1 generation consisted of LR 

 males and females. The LR 9 were removed from their brothers 

 and crossed with pure BfW males. This was done in order to 

 secure four possible classes, in the F 2 generation, not only of 

 males but also of females thus rendering the female counts also 

 available for study. 



Table XV. shows the gametic constitution of the flies used and 

 the combinations expected in the F 1 and F 2 generations. 



TABLE XV. 



To ILLUSTRATE EXPERIMENT VIII. 



P> LRX - LRX = LR9 BfWX - o = BfRo" 



Gametes LRX BfWX, o 



F 1 LRX -- BfWX = LR 9 LRX - o = LRc? 



LR9 of F 1 X BfWcf (from stock) 



f (i ) LRX, (2) BfWX, f BfWX. o 



Fi Eggs^ Tnrv . _,_ v Sperm X 



F 2 LRX - BfWX = LR9 LRX - o = LRtf 



BfWX -- BfWX == BfW 9 BfWX - o = BfWcf 



LWX -- BfWX = LW9 LWX - o = LWd* 



BfRX - BfWX = BfR9 BfRX - o = BfRd" 



Iii Table XVI. are given the actual results of the experiment. 

 Judging from the total numbers of the F 2 flies the break in the 

 coupling occurs in the ratio of 5 per cent, in both females and 

 males. Only the normal range of variations from this are ap- 

 parent when the numbers from individual bottles are considered. 1 



1 In the previous experiments 4-6 females were placed with as many males in 

 the same bottle. For Experiments VIII. and IX. one female with 2-3 males was 

 placed in a bottle. She and the males were transferred every 6-8 days. Some 

 of the females lasted for six weeks by which time they were fairly exhausted of eggs. 



