No. 578] DROSOPHILA AMPELOPHILA 107 



Pinlc Heterozygous $ by (Brother) Bed # 



It will be seen that all the red flies of the last cross were 

 heterozygous, and should give, on further inbreeding, a 

 ratio of 3: 1. Four pairs out of five (one being sterile), 

 taken from Pair III of Table IX, gave the following: 



Pair "a" above gave the same result as pair "A" 

 (Table VII)— the ratio in each case being 7.5 : 1. The off- 

 spring of the latter were found to contain a high percent- 

 age of sterile pink flies, owing to which the attempt then 

 made to test that ratio failed. It was therefore decided 

 to repeat the same experiment with the offspring of this 

 "a" pair. As in the former case, the heterozygous red 

 flies were picked out by crossing them to their pink 

 brothers and sisters. The expectation was again 1:1. 

 The records follow. 



TABLE XI 



Record of Eight Pairs, Heterozygous Red x to Pink, Taken from thk 



