432 p. W. WHITING 



Among the 1873 moths there recorded, are 1064 sooty, 398 

 type, 103 sooty black, and 307 black. There are 1463 gray to 

 410 black, showing a slight deficiency of black, the expectation 

 being 1405 to 468. Among the gray the proportion, 1064 sooty 

 to 399 type, shows a slight excess of type, the expectation being 

 1097 to 366. Among the black the ratio, 103 sooty black to 

 307 black, is remarkably close to 102.5 to 307.5, the expectation 

 with a reversal of dominance. 



Summarizing the Fo generations from pair (125) (SS.BB cf X 

 ss.bb 9) and pah* (127) (SS.bb d^ X ss.BB 9), we have 1282 

 sooty, 477 type, 120 sooty black, and 364 black, where the ex- 

 pectation on a 9:3:1:3 basis is 1261.8:420.6: 140.2: 420.6. 

 The divergence from the expected ratio is largely due to the 

 deficiency of black. There are in all 1759 gray to 484 black, 

 the expectation being 1682 to 561. Considering the gray alone, 

 there are 1282 sooty to 477 type, the expectation being 1319 to 

 440. Considering the black alone, there are 120 sooty black to 

 364 black, the expectation being 121 to 363. 



A convenient method of expressing dominance in a reversal 

 of this sort is to reverse the relative positions of the symbols 

 placing the small letter before the large. In writing the formula of 

 a phenotype alternative possibilities may be expressed by symbols 

 in parentheses. Thus a moth typical in appearance would be 

 either ss.BB or ss.Bb, expressed ss.BB(b): a sooty would be 

 SS(s).BB(b): a sooty black would necessarily be homozygous, 

 SS.bb: and a black would be ss(S).bb. 



Pairings were made of moths from the F2 or segregating gener- 

 ations from matings (125) and (127). The genetic composition 

 of these moths must be inferred from their appearance and the 

 character of the fraternities produced. The results are of in- 

 terest, since they corroborate conclusions concerning the heredity 

 of sooty and black. 



Each of four pairs of sooty by sooty produced only sooty, 246 

 in all, showing that each pair must have been SS X SS(s) and 

 BB X BB(b). 



Each of four pairs of sooty by sooty black produced only 

 sooty, 275 in all, showing that each pair must have been 

 SS(s).BB X SS.bb. 



