34 HEREDITY OF SKIN COLOR IN NEGRO-WHITE CROSSES. 



Table 30. Distribution of eye color in offspring of parents with given amount of iris 



pigmentation. Continued. 



(L) DARK BROWN X BROWN. 



Since our matings did not include two pure blue-eyed parents, 

 the simplest case of heredity (the mating of two negatives) can not 

 be tested here. Hazel we have regarded as usually a simplex (hetero- 

 zygous) condition, and on this hypothesis two hazel parents should 

 produce blue-eyed, brown-eyed, and hazel-eyed offspring again; but 

 until we know how many factors are involved in brown iris color we can 

 not say in what percentage of cases blue should reappear. Actually, in 

 section (A), in 9 offspring there is 1 case of dark brown iris; none of 

 blue, and 5 of hazel again. But in sections (E) and (/), when hazel 

 is used as one parent, a few blues appear in the offspring; actually 

 6 in 87. On the hypothesis of two factors for black in eye color we 

 might expect 1 child in 4, in these two matings, to be blue-eyed. On 

 the hypothesis of four factors for black in eye color we should look for 

 1 blue-eyed child in 16. The actual result favors the hypothesis of four 

 factors for black in iris pigmentation of negroes. Brown X brown gives 



