w 



302 THE SECOND-CHROMOSOME GROUP 



The locus of apterous is about 2 units to the right of black, or at 

 approximately 48.8. 



Cream II and patched were found to be linked, but their positions 

 with respect to the other loci were not found. 



The position of trefoil is around 50 units from star. 



The corrected star cream h value of 22.5 gives the locus of cream b 

 directly. 



The gene for pinkish is located in the far right end of the chromosome, 

 but the locus has not been accurately determined. 



The plexus speck value of 8.7 is at present the only acceptable infor- 

 mation on the precise location of plexus, which is thus at a locus of 96.2. 



' ' ' 1 ' n-T^H 'i l l ' — I ' ' 1 II ' I j iir : 



O ifk in b b in i" "~Ju'l'+ s in b u' w n b>i» 



MWm^-u. 



© 



'^' K Cd) S^ (S) W"^ c f/-^a 



1 1 r 





na (fp) 



crb T' aip^tf tg 



Text-figure 87. — Constructional map of second chromosome, giving bases of reference and 

 indicating various cross- over values used in calculating mean position for each locus. 



The locus of limited is either the same as that of morula, which is 

 possible, or is slightly to the right. 



The black fringed value of 42.5 is almost the same as the black arc 

 value of 42.6, so that we may place fringed at 98.0. 



The locus of dachs-lethal is probably the same as that of dachs, 

 29.0 (dachs-deficiency) ; but if this is not the case, then the locus is so 

 close to that of dachs that the interval is negligible. 



Squat gave 11.0 per cent of crossing-over with black and can there- 

 fore be mapped at 35.5. 



Lethal Ila gave a value of 13.0 with black, and a value of 8.7 with 

 curved. In the first case there were 166 flies, indicating a position of 

 59.5; and in the second case 249 flies, indicating a position at 64.8. 

 The mean position is thus 62.7. 



The position of telescope is known only from the star telescope 

 back-cross value of 44.4, which indicates a locus at about 66.5 (C = 100). 



The loci of the various mutant genes with respect to black as a base 

 of reference have just been found. In some regards it is more con- 

 venient to renumber these loci so that the left-most (star) is taken as 



