A NEW GENE IN DROSOPHILA. 



2O9 



of this nature. In the following table the calculation for each 

 culture and for the total is given. 



Wild X black curved 



Fi 9 X black curved cf cf. 



610 



184 



226 



652 



24.5 



Similar tests' of FI females from the converse cross of black X 

 curved gave: 



Per Cent, 



of Crossovers. 

 28.8 

 31.6 



20. 8 



18.7 

 21.4 

 18.3 

 19.0 

 17.2 

 18.4 

 15.2 

 25.4 

 27.1 

 23.9 

 24.8 



644 



2,292 



2,148 



663 



22.7 



Adding the figures from these two converse experiments gives 

 1,717 crossovers in 7,419 flies, or 23.1 per cent., of crossovers. 

 Because of double crossing over, which is known from unreported 

 experiments to occur within this distance, 23.1 is slightly less 

 than the actual chromosomal distance apart of these two loci. 1 



It will be seen from the two above tables that there is appar- 

 ently a rather wide range of variability in the percentage of 

 crossing over in different cultures. This variability is much 

 greater than one would expect to find if it were due entirely to 



1 See Sturtevant (Jour. Exp. Zoo/., '13) for a discussion of linear series of genes 

 within a chromosome. 



