110 T. H. MORGAN 



The meaning of the high sex-ratios that appeared in these 

 cases must remain therefore unknown, and it is idle to speculate 

 whether the results are or are not due to a non-sex-linked lethal, 

 a sex-linked partial lethal, a sex-limited factor or factors, etc. 

 The importance of following up this case was not appreciated 

 at the time and this line was not continued except to breed seven ' 

 individuals from No. 39^ (table 21). 



Data from stock of Lethal II 



The stock that carries Lethal ii has been maintained by breed- 

 ing long red females to white or to eosin miniature males from 

 the regular eosin miniature stock. This has been continued to 

 the present time. The results are shown in the next table, where, 



_W Ig V 



X X 



6 1 



tjgure E 



through ten successive generations (bred in pairs), the inherit- 

 ance of a 2:1 ratio has maintained itself. The horizontal lines 

 in the first column separate generations; in some cases two or even 

 three lines were tested, in each generation, in other cases only 

 one. In all there are 13,749 flies recorded. The sex-ratio is 

 2.3:1. The order of the factors is shown in figure E. The 

 percentage of cross:-overs between white and lethal is 8.8, that 

 between lethal and miniature is 16.3; and that between "white 

 and miniature is 24.7 which agree sufficiently with the per- 

 centages already given. The females are also available for 

 cross^overs between white and miniature, and these give 28.3. 



The linkage of Lethal II with white {or eosin) and with miniature 



The diagram (fig. C) on page 103, will serve to recall the 

 order in which the three pairs of factors enter. The Fi female 

 has received from her mother a sex-chromosome, bearing the 

 factor for red (W) Lethal ii (I2) and long wings (M) ; and a sex- 



^ No. 39 is peculiar in that eosin miniature and red miniature males are too few 

 in numbers. 



