No. 578] DROSOPHILA A MP EL PHIL A 



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F 2 Record from Red-e 



TABLE VIII 



'lies Crossed to : 



A comparison of Tables VI, VII and VIII suggests the 

 possible presence of high and low pink-producing 

 "strains" in these stocks. To test this, some of the off- 

 spring of pair A (Table VII) in which the ratio was 7.5 

 of red to 1 of pink, were inbred for the F 3 in order to see 

 if the same ratio would persist. As there were among the 

 red both homozygous and heterozygous forms, they were 

 each mated to their pink sisters or brothers. This com- 

 bination would give with the former all red (since red is 

 dominant) and with the latter a ratio of 1: 1. 



Pair F (Table VII) in which the ratio was ideal, 3:1, 

 was chosen for the control, and treated in like manner. 



In this as in the preceding experiment the flies were 

 mated in pairs and transferred to fresh bottles every 

 second or third day. A peculiar thing happened. Out of 

 25 pairs taken from "A" only two gave offspring; the 

 remaining 23 pairs were apparently sterile. It could not 

 have been due to bad banana or any other unfavorable 

 condition, for the flies had already been transferred five 

 times and no pupse were found in any of the other bottles. 

 Furthermore, the 16 pairs of the control which ran paral- 

 lel to them, and were fed with the same food, did well. 



