92 



T. H. MORGAN 



TABLE 8 



If lethal is between yellow and miniature the double cross- 

 over class is gray long. The data of table 8 shows that this is 

 the class not represented in the males, and the result is in har- 

 mony with the view that the order of factors is yellow, lethal, 

 miniature. Furthermore, these data give us the distance of 

 lethal from yeUow tIt or 0.7, which is the expectation if lethal 

 lies between yellow and white and at a distance of 0.4 from white 

 (1.1 — 0.4 = 0.7). Both experiments taken together show by 

 the agreement in linkage, and in the absence of particular classes 

 that the chromosomal line-up is yellow, lethal, white, miniature. 

 This linkage of 0.4 is the strongest met with so far, correspond- 

 ing to a 'gametic ratio' of about 250 : 1. 



The reappearance of Lethal I 



In 1914 a cross was made between yellow white normal females 

 and gray red abnormal males. The cross gave in the Fi gener- 

 ation yellow white males and abnormal females. No disturb- 

 ance of the sex-ratio was noted, although it was not looked for 

 specifically. Thirteen Fi matings in pairs were made. Three 

 of these pairs gave a sex-ratio of two females to one male. 



180 



176 



170 



