OF MUTANT CHARACTERS. 271 



Table 122. — Summary of all cross-over data involving s/ar— continued. 



Date. 



Nov. 17, 1915 



July 11. 1915 

 Dec. 15. 1915 



May 21. 1916 

 July 20. 1915 

 Oct. 23. 1915 



Sept. 23, 1916 



June 28, 1915 

 July 11.1915 



By- 



Bridges 



Do. 

 Plough 



Bridges 

 Do. 

 Do. 



Do. 



Do. 

 Do. 



Rfforence. 



Tgn; 

 S'; - 



S' 



B.C.; laNe 123. 

 ^ "»" thia paper. 



B.C.. lulu: IS,3<^ 



P^C'P lstt4. 



J. E. Z.; '17. p. 147; teniiMrrft- 



S'' 

 tures; ' — B.C.; tabic* 7 



be 

 (n"). SK^o). 8.(8"). Ill 

 («"). 17,. 



t»; — B.C.;4632-'.-J5. 



Px/—- B.C.; 192l-'24. 



6 Px 



S' 



fr; 'B.C. ; 22.82-'84. 



b fr 



S' 



Pinkish; 



B.C.; 5267. 



pinkish 

 S'; S' sp B.C.; lH06-'07. 



firsts; 1836- 



P' *" *" 1894. 



necting-link between that body and the other relatively poorly estab- 

 lished loci of the experiment. 



There was on hand a complex stock containing the two genes — 

 streak and dachs (provided by Muller) — and this was used in the Pi 

 mating to star purple, which was made for that purpase. The Fi 

 star streak females were back-crossed to males of a stock of dachs 

 purple which was brought to production simultaneously with the Fi 

 cultures (table 121). 



In making the classification of the flies produced by the quadruple 



back-cross 



.S" 



Pr 



St d 



the first separation performed was that of 



streak, disregarding the other characters, and including as streak only 

 those quite obviously streak. These precautions prevented the classi- 

 fication of any not-streak flies among the streak, and established a 

 uniform standard for streak among all the various classes. 



The separations were of varying degrees of difficulty in the different 

 cultures. The hardest were 4999 and 5040, which were fully iis diffi- 

 cult as in the abandoned streak dachs back-cross. On the other lumd, 

 the separations in culture 5110 were perfectly sharp and complete. 



The streak flies totaled 396, and the calculation of the cross-over 

 values on the basis of these flies gave a star streak value of 15.9 units, 

 a streak dachs value of 16.2, and a streak purple value of 28.S (table 

 121). 



