438 T. H. MORGAN AND C. B. BRIDGES 



white pink 9 Xwp — Xw p 

 ^ redcf XWP P 



* Culture I gave in addition seven white females and six red males. Culture 

 II, gave one white female and two red males, Culture III, one white female and 

 three red males, and Culture IV gave two white females and eight red males. 

 Each of these cultures was obtained by mating five virgin females of pure white 

 pink stock to several wild males. 



All the red females heterozygous for white and pink which 

 have been observed fail to show any dilution. 



Red heterozygous for eosin and vermiliori 



When red females are mated to eosin vermilion males the 

 daughters are red heterozygous for eosin and vermilion. The 

 sons are normal red in compositidn and color: 



p red 9 XWV — XWV 



eosin vermilion cf X w® v — 



- ^ 



Fi female Fi male 



XWV XWV 



Xw«v 



red 9 red cf 



200 189 



These Fi red-eyed females have the same eye color as the nor- 

 mal Fi males, although heterozygous for two factors. In this 

 case the Fi females were mated back to the eosin vermilion males 

 and gave in the next generation 1279 red of exactly the same com- 

 position as F2. Here again no difference from the normal could 

 be discovered. 



The gametes of the Fi female and of the Pi male used in the 

 back cross are as follows: 



