246 



Sturtevant. 



The results of back -cross tests of females (table XMII) are 

 summarized in table VI. One set of experiments is omitted, for reasons 

 which will appear when it is discussed later. The reason that only one 

 experiment was carried out involving two of the wing mutants (loci Vg, 

 Cv, Ba) was that in none of these cases is the double recessive distingui- 

 shable from vestigial or from balloon, as the case may be. 



The BSp figures are derived from a cross in which Cv was also 

 involved. Several attempts were made to get the double recessive hasp, 

 in order to work out the linkage of these genes, but without success, 

 indicating that the loci are very near each other. Since Ba has been 

 used only with B its position can not be accurately determined, but as 

 BSp is greater than BBa by I'O I have placed Ba, tentatively I'O 

 nearer B than is Sp in Fig. 3^). 



B 



-t— 



Vtf 



— t— 



Cv 



BaSp 



— H — 



Zlt 



30.7 



as» 3U 



Fig. 3. 



Table VII shows for chromosome II what table 11 does for chromo- 

 some I — namely, the relation between observed percent of crossing over 

 and "distance", as calculated without allowance for double crossing over. 



The data are not so extensive or reliable as those obtained for 

 chromosome I, but on the whole the same general relations seem to hold. 



Double crossing over in Chromosome II. 



Table XX shows two crosses which give data for a study of double 

 crossing over in chromosome 11. The results obtained are shown in 

 table Vni. 



Table VII. 



*) Other data indicate that, in reality, Ba is probably a little further from B 

 than is Sp. 



