298 



THE SECOND-CHROMOSOME GROUP 



plus direction from black, were those lying on the same side of black 

 as does curved, which was the first locus to be included with black in 

 the second chromosome. Likewise the loci "to the left," or in a 

 minus direction, were those lying on the opposite side of black from 

 curved. 



However, curved is too remote from black to be accurately located 

 by direct reference to black. Accordingly, the position of these inter- 



Table 140. — Summary of available data on crossing-over in the second 



chromosome. 



Loci. 



Star streak 



Star cream b 



Star truncate. ... 



Star black 



Star apterous 



Star purple 



Star vestigial 



Star curved 



Star trefoil 



Star telescope . . . . 



Star plexus 



Star fringed 



Star pinkish 



Star speck 



Streak dachs 



Streak black 



Streak purple 



Streak vestigial. . . 

 Streak curved . . . . 

 Streak blistered. . . 



Streak speck 



Streak balloon . . . . 

 Streak morula . . . . 



Dachs black 



Dachs purple 



Dachs vestigial . . . 

 Dachs curved. . . . 



Dachs speck 



Dachs balloon . . . . 



Sfjuat black 



Squat plexus 



Total. 



16, 



8, 



19, 



1, 



2, 

 2, 



6, 

 1, 

 5, 



396 

 389 



549 

 507 

 169 

 155 

 450 

 870 

 154 

 531 

 352 

 496 

 175 

 135 

 858 

 462 

 665 

 462 

 269 

 11 

 462 

 462 

 876 

 725 

 489 

 354 

 462 

 462 

 462 

 82 

 82 



Cross- 

 overs. 



63 



86 



149 



6,250 



83 



3,561 



195 



9,123 



65 



236 



632 



274 



74 



3,448 



109 



120 



883 



164 



923 



5 



242 



242 



405 



1,196 



293 



1,585 



145 



231 



231 



9 



39 



Per 

 cent. 



15.9 

 22.1 

 27.1 

 37.9 

 49.0 

 43.7 

 43.3 

 45.9 

 42.2 

 44.4 

 46.7 

 55.2 

 42.3 

 48.3 

 12.7 

 26.0 

 33.1 

 35.5 

 40.7 

 45.0 

 52.3 

 52.3 

 46.3 

 17.8 

 19.7 

 29.6 

 31.4 

 50.0 

 50.0 

 11.0 

 47.6 



Loci. 



Black jaunty. . . . 

 Black purple .... 

 Black lethal Ila . 

 Black vestigial . . 



Black curved 



Black plexus. . . . 

 Black fringed . . . 



Black arc 



Black blistered. . 

 Black pinkish ... 



Black speck 



Black balloon ... 

 Black morula . . . , 

 Purple vestigial . . 



Purple curved 



Purple plexus. . . . 



Purple arc , 



Purple speck 



Purple balloon . . . 

 Lethal IIo curved 

 Vestigial curved . . 

 Vestigial speck . . . 

 Vestigial balloon., 

 Curved speck . . . . 

 Curved balloon . . 



Plexus speck 



Arc speck 



Arc morula 



Blistered speck . . . 

 Speck balloon . . . . 



Total. 



462 



48,931 



166 



20,153 



62,679 



2,460 



496 



7,592 



224 



736 



685 



2,236 



7,549 



13,601 



51,136 



344 



2,625 



11,985 



462 



249 



1,720 



2,054 



462 



10,042 



462 



.327 



2,625 



6,794 



36 



462 



Cross- 

 overs. 



Per 



cent. 



1? 



3,026 



22 



3,578 



14,237 



1,031 



211 



3,2.37 



93 



371 



326 



1,073 



3,518 



1,609 



10,205 



164 



1,066 



5,474 



218 



22 



141 



738 



178 



3,037 



150 



29 



156 



634 



3 



2 



0.2? 



6.2 

 13.0 

 17.8 

 22.7 

 41.9 



42 



42 



41 



51 



47.6 



48.1 



46.6 



11.8 



19.9 



47.7 



40.6 



45 



47 



8 



8 



35 



38.5 



30.2 



32.5 



8.9 



5.9 



7.9 



8.3 



0.4 



mediate bases must first be mapped. Of these, purple was the first 

 to be considered as being the closest to black, and also because its 

 position with relation to black has been the subject of more investi- 

 gation, and is more accurately determined than any other second- 

 chromosome distance. The black purple cross-over value of 6.2 is 

 based on 48,931 flies, and since there is certainly no double crossing- 

 over within this distance, the value can be accepted without correction, 

 and purple can be mapped at a locus 6.2 units to the right of black. 



The third locus to be considered is vestigial, and there are open two 

 sets of data by means of which the position of vestigial can be mapped : 

 (1) the position of vestigial can be located directly by the purple 



