OF MUTANT CHARACTERS. 



255 



The black arc morula stock was found to be showing the limited 

 band character in all or nearly all of the morula flies, and this condition 

 has been maintained for some five years, which means that the linkage 

 is very close. It is in fact not entirely certain that limited may not 

 be found to be still another effect of morula itself. 



CONFLUENT (Q). 

 ORIGIN OF CONFLUENT. 



In culture 550 (which was part of the tests of the method of trans- 

 mission of the ability to produce exceptions by non-disjunction), 

 Bridges found a single male which had thickened, knotted veins 

 in the wing (September 23, 1914). The vein most thickened was 

 the second longitudinal opposite the anterior cross-vein, but especially 

 at the tip, where it was confluent for quite a space with the marginal 

 vein. In addition both cross-veins were thickened and irregular. 

 The wing as a whole was slightly smaller than usual and the fly 

 seemed rather sluggish. 



INHERITANCE OF CONFLUENT. 



This male was out-crossed to a wild female and in FI produced 

 nearly half of the offspring with confluent veins (culture 592, table 

 102). From this FI result confluent was known not to be sex- 

 linked, since the characters appeared in half the FI males as well as 

 females, instead of in none of the males and all of the females, as it 

 would have done had it been a sex-linked dominant (like bar). 



TABLE 102. Confluent cf (heterozygous) X wild 9 . 



Some of the FI confluent males were again out-crossed to wild 

 females, and all the cultures of similar character (table 102) gave a 

 total of 600 flies, of which 291 or 48.5 per cent were confluent. Thus 

 the viability of confluent is not bad, though the sterility is very high. 

 Very many such matings failed, and this was especially true of the 

 confluent by confluent matings. 



The confluent by confluent matings gave consistently about two- 

 thirds of the flies confluent and one-third wild-type. This suggested 

 that, like streak, confluent was lethal when homozygous. 



