EYE COLOR AND HAIR COLOR IN MAN. 53 



gametes present in equal numbers with the carriers of the darker 

 colors we should expect to find light eyes in one fourth of the 

 population. In a population in which over half the individuals 

 fall into the light-eyed class it is evident that a much greater 

 proportion than two thirds of the dark-eyed class are hetero- 

 zygotes. In the 395 offspring tabulated the color of eyes was 

 as follows : black 29, brown iio, hazel 3, gray 93, green 10, 

 blue 150. It is safe to assume that much over three fourths of 

 the dark-eyed individuals are heterozygotes but it is impossible 

 to make more than a rough estimate of the ratio from the data at 

 hand. In crosses of brown x blue we should expect half the 

 offspring to be brown even if all the browns were heterozygous. 

 If some of the browns were dominant the proportion would be 

 greater. As a matter of fact we get 48 blacks or browns to 69 

 of the gray-blue class which is very different from the expected 

 Mendelian ratio. 



In crosses of brown x gray we get 30 of the dark class to 17 

 of the light which is more in accordance with the Mendelian ex- 

 pectation. In the black x blue crosses we get 30 of the dark 

 color to 18 of the light which is very close to the preceding 

 result. Black x gray gave 13 dark to 8 light. 



Much of the data obtained may be interpreted as illustrating 

 Mendelian inheritance but it is by no means certain that it should 

 be so interpreted. There are, on the contrary, several cases 

 which refuse to come under the Mendelian formula. There are 

 indications that the inheritance is to a certain extent of the blended 

 type. Crosses of brown or black with gray give a relatively 

 greater number of browns than do crosses of brown or black with 

 blue. Since gray frequently contains a certain amount of melanin 

 pigment it is readily understood, if the inheritance is partially 

 blended, why many more offspring should be raised into the 

 brown category than in the crosses with blue. Again, compare 

 the crosses of black x blue with those of brown x blue. In the 

 former the proportion of blues is small, 4 out of 48, where the 

 Mendelian expectation (if the blacks are predominantly hetero- 

 zygous) is much greater. In the latter 46 out of 1 17 are blues. 

 This can hardly be accounted for by any difference in the propor- 

 tion of heterozygotes between the blacks and browns, which is 



