NEW DATA. 



CLUB. 



6 9 



In May 1913 there were observed in a certain stock some flies which, 

 although mature, did not unfold their wings (text-fig. H<z). This con- 

 dition was at first found only in males and suspicion was aroused that 

 the character might be sex-linked. When these males were bred to 

 wild females the club-shaped wings reappeared only in the F 2 males, but 

 in smaller number than expected for a recessive sex-linked character. 

 The result led to the further suspicion that not all those individuals that 

 are genetically club show club somatically. These points are best illus- 

 trated and proven by the following history of the stock: 



Club females were obtained by breeding F 2 club males to their F 2 

 long-winged sisters, half of which should be heterozygous for club. 



FIG. H. Club wing, a shows the unexpanded wings of club flies; c shows the absence of the two 

 large bristles from the side of the thorax present in the normal condition of the wild, b. 



When the F 2 club females and club males were bred together, instead of 

 only clubs being produced, long-winged flies also appeared. In fact, 

 only about a third of the offspring showed the club character. 



Club females bred to wild males gave some club males in FI (although 

 most of the males had long wings), and in F 2 some of the females and 

 some of the males were club. In all essential points club shows the 

 characteristic features of a sex-linked recessive, except that it is realized 

 in only a small proportion of the individuals that are genetically club. 



These general statements are substantiated by the following data: 

 Club male by wild female gave in 20 F 2 mass cultures, wild-type 9 , 



