424 p. W. WHITING 



A pair of dark produced 73 gray and 23 black, which is close 

 to the three to one ratio expected from heterozygote by heterozy- 

 gote. Again the grays showed much gradation between dark 

 and type. 



Another pair of dark produced 13 dark in which the character 

 was very pronounced showing no gradation toward type. 



A black male paired with a type female produced 14 gray 

 grading from type to dark and 14 black. 



Another pairing of black male by type female produced 24 

 gray, all of which showed the dark mid-area. In these two 

 matings dark was evidently introduced with black, 



c. Sooty base. Sooty base acts as a simple dominant to type, 

 but its separation from type is sometimes rendered difficult by 

 the presence of dark mid-area and other variations. This is 

 more fully considered in another section. Only those fraterni- 

 ties in which the distinction from type was clear are here 

 summarized. 



Three pairs of homozygous sooty by type produced 430 sooty. 

 Dominance was practically, although not quite, complete. 



Two pairs of sooty produced 42 sooty. 



Six pairs of heterozygous sooty by type produced 77 sooty 

 and 93 type. The deficiency of sooty below the one to one 

 ratio is to be noted. 



Thirty-eight pairs of heterozygous sooty produced 1627 sooty 

 to 615 type where 1681.5 to 560.5 is to be expected. Again the 

 deficiency of sooty is to be noted. 



No significant variation in ratios in cultures segregating sooty 

 and type could be found. This is in marked contrast to the 

 condition noted in regard to black. 



2. Heredity of oral defects, a. Cleft tongue. The masking of 

 a Mendelian difference by environment. The appearance of 

 cleft tongue is much complicated by environmental conditions. 

 Certain strains never throw cleft, while in others cleft occurs in 

 variable ratios. It has been noticed that fraternities containing 

 moths with cleft tongue show cleft emerging in large numbers 

 at certain times and scarcely at all at others. The cultures have 

 been shifted from humid to comparatively dry conditions and 



