334 



MUTATIONS IN EYE-COLOR OF DROSOPHILA. 



to it 



1 





But if one or two females were left behind they would go over with the F 

 flies and contaminate the second generation. As a rule the parent flies are left 

 for ten days in the first culture bottle, and then taken out and destroyed or placed 

 in a new bottle. On the eleventh or twelfth day the F 2 flies begin to appear and 

 are removed daily for the next ten days, when the bottle is thrown out, for fear 

 that F z flies might appear. In this way the overlapping of generations is avoided. 

 In addition to the preceding mass cultures the next table gives the counts of 

 twenty pairs. The results run as evenly as those of the mass cultures and show 

 that the former represent the actual outcome of the cross; i. e., they show the 

 same range of variability. 



9 by P <? 



P 9 



o a 



\/ 



l 



2 



3 

 4 



5 

 6 

 7 

 8 

 9 

 10 

 11 



1 P9 



Pd" 



1 09 



0<? 



50 



38 



46 



34 



22 



22 



14 



23 



7 



6 



1 



5 



21 



27 



35 



25 



53 



37 



38 



55 



30 



24 



21 



24 



29 



24 



28 



30 



13 



16 



13 



17 



27 



34 



29 



32 



53 



52 



46 



42 



34 1 



1 36 



30 



24 



OcT 



34 

 21 



20 

 34 

 24 

 31 

 18 

 4 

 17 



516 



The reciprocal experiment, in which the pink female is paired to the orange 



male, was also repeated with the following results 



Pink 9 by Orange <? 



JPink 9 1,2641 



I Pink 



& 



976 J 



Pink 

 Pink 



9 437 

 cf 217 



Orange c? 184 



These results agree with those of the earlier experiment. When the F 2 flies 

 of both experiments are added together they give the following result : 



Pink 

 Pink 



Orange cf 



9 1,472 



729 

 702 



cT 



F 



2 



■ 



Pink-Orange Back-Crosses 



Other Tests 



The correctness of the formulae can be tested in several ways by back-crossing, 

 counter-crossing and out-crossing. The following results show convincingly the 

 correctness of the symbolism used. I do not doubt that the results might be 

 formulated in a different way, but the principle involved would remain the same, 

 and it is the principle involved rather than the particular way of expressing the 

 relation that is the important point at issue. 



