152 



ROBERT CHAMBERS, JR. 



For the sake of simplicity these factors will be considered in 

 this paper as single units. 



EXPERIMENT I. 



A long-winged vermilion eyed female was mated with a bifid 

 winged red eyed male. The results to be expected in the F l 

 and F 2 generations are shown in Table I . 



TABLE I. 



To ILLUSTRATE EXPERIMENT I. 



LVX - LVX = LV 9 

 P 1 Eggs LVX 



F 1 





LVX - BfRX = LR 9 



f (i) LVX, (2) BfRX, 



' LRX, (4) 

 LVX- LVX ! 

 BfVX - LVX / 

 BfRX - LVX ) 

 LRX - LVX 



BfRX - o = BfRc? 

 Sperm BfRX, o 



LVX - o = LVd" 

 LVX. o 



LVX - o = LVc? 

 BfRX - o = BfRcf 



LRX - o = LRo" 

 BfVX - o = BfVcf 



The F 1 generation consisted of LR females and LV males. 

 The actual results of the F 2 generation are shown in Table II. 



TABLE II. 



RESULTS OF EXPERIMENT I. 



All the combinations expected are realized. Owing, however, 

 to the coupling in pairs of the P 1 factors, the numbers of males in 

 the two classes consisting of the combinations LR and BfV are 

 fewer than those of the other two classes. That they appear 

 at all is evidence of the incompleteness of the linkage, the new 

 combinations being due to a rearrangement or crossing over of 

 factors within the germ cells of the F 1 flies. The strength of 

 linkage may be determined by that percentage of the total which 

 are crossovers, in this case 112/379 or approximately 30 per cent. 



On mating the F- males possessing the new combination BfV 



