56 



SEX-LINKED INHERITANCE IN DROSOPHILA. 



LINKAGE OF VERMILION, BAR, AND FUSED. 



Males from the stock of (red) bar fused were mated to vermilion 

 (not-bar, not-fused) females, and produced bar females and vermilion 

 males. The bar Fi daughters were back-crossed to vermilion fused 

 males and produced the classes of offspring shown in table 34. 



Table 34. — Pi zermilion 9 9 X bar fused cf cT. B.C. Fibar 9 X vermilion 



fused cf cf- 



The data show that the factor for fused lies about 3 units to the right 

 of bar. This is the furthest point yet obtained to the right. The 

 reasons for locating fused to the right of bar are that, if it occupies such 

 a position, then the double cross-over classes (which are expected to be 

 the smallest classes) should be vermilion bar and fused, and these are, 

 in fact, the smallest classes. The order of factors is, then, vermilion, 

 bar, fused. This order is confirmed by the result that the number of 

 cross-overs between fused and vermilion is greater than that between 

 bar and vermilion. 



In order to obtain data to balance viability effects, the following 

 experiment was made: 



Vermilion (not-bar) fused males were bred to (red) bar (not-fused) 

 females. The daughters and sons were bar. The daughters were 

 back-crossed, singly, to vermilion fused males and gave the results 

 shown in table 3 5. Each female was also transferred to a second culture 

 bottle, so that for each female there are two broods given consecutively 

 (82, 82', etc.) in table 35. 



The results given by the two broods of the same female are similar. 

 The values are very near to those given in the last experiment, and 

 confirm the conclusions there drawn. The combined data give the 

 results shown in table 36. 



