A NEW GENE IN DROSOPHILA. 



207 



of one sex to the curved of the other sex. In FS if there has been 

 crossing over in the FI 9 there should appear some of the double 

 recessives or some single recessives heterozygous for the other 

 single recessive. In fact some blacks appeared which gave, in F 4 , 

 3 black : I black curved. From these black curved individuals 

 a pure stock of the double recessive was obtained directly. 



That the absence of black curved flies in F? was really due to 

 lack of crossing over in the male was shown by making "back- 

 cross" tests of doubly heterozygous males as follows: 



Black X curved. 



I 

 Fi cf cT X black curved 9 9 . 



Wild Type. 

 O 



o 







o 

 o 

 o 

 o 







o 



From the converse cross of wild by black curved described 

 below, two tests of FI males were made, with the following 

 results: 



Wild X black curved. 



Fi c? c? X black curved 9 9 . 



Wild Type. 

 108 



Black. 

 O 



O 



Curved. 

 O 



O 



Black Curved. 

 88 



57 



179 



145 



No new combinations of characters (crossovers) appeared in 

 the i, 066 flies from the two converse experiments. This is in 

 exact agreement with Morgan's results on black vestigial, and 

 is somewhat more significant, since, as will appear below, there 



