358 



CALVIN B. BRIDGES 



In order to see if the experiment would still give the two 

 kinds of results observed before, several Pi matings (cream III 

 ebony cf X eosin 9 ) were made, and each father was saved and 

 remated to one of his daughters. Of six such tests five gave the 

 low value and one the high (table 16). The low values corre- 

 sponded to the expected result that the Fi females should be 

 heterozygous for Cm. 



TABLE 16 



The B. C. offspring of cream III ebony males outcrossed to eosin females (pairs) 

 and then remated each to a single daughter 



1 The two cultures 2774 and 2776 produced only half as many sons as daughters 

 "Owning to the occurrence of a lethal (lethal 11), the mutation for which must 

 !'have taken place in the eosin stock some time before. 



2 Culture 2778 gave rise to a mutant 'roof wings' which likewise had originated 

 ■iin the eosin stock. 



That backcrosses made up from the low crossover cultures 

 continued to give only low values is shown by table 17. The 

 occurrence of a high value among such cultures would have been 

 an indication that one of the cream III ebony males previously 

 used had failed to be homozygous for Cm. 



