No. 508] HEREDITY OF HAIR COLOR IN MAN 199 



light brown or lighter. Were the dark brown parents 

 triily homozygous in hair color, and did the hair color of 

 the offspring not grow darker with age, Mendelian ex- 

 pectation would be 100 per cent, dark brown. Actually, 

 the result falls far short of that, just as the necessary 

 conditions are far from being met. It is highly probable 

 that in some of these families (notably Gil-B, Gue and 

 Huf, and probably also Lat-A and Wil-D) the darker 

 parent actually forms germ cells that lack black pigment. 

 Of the four lightest haired children the ages of three 

 that are known are 8, 10 and 15 years— ages at which the 

 adult color is not fully shown. Under these circum- 

 stances one can not predict with certainty the outcome 

 of matings of this class. One can only say that the 

 proportions of light brown children and those with lighter 

 hair should be less in proportion to the darker haired 

 children in class B than in class A. The actual propor- 

 tions in the two classes are in the direction of this ex- 

 pectation. 



Table V. Distribution of Hair Color in the Offspring when One 

 Parent has Black Hair and the Other Light Brown Hair 

 (No Division, on Account of Fewness of Families) 



Assuming what is probably true tor an m« 

 that the black-haired parent produces an equal number ot 

 germ cells with a tendency toward lighter hair and toward 

 ! should expect an approach toward an equality 



what is probably true for all the families 



, . ,„T -rmmhpr f>i 



black, 



