No. 508] HEREDITY OF HAIR COLOR IN MAN 197 



pigment has a weak intensity in the parents it will have 

 the same character in the children; but where it has a 

 strong intensity, as red, in the parents it may have the 

 strong intensity in some (Swe) or all (Edw) of the 

 children. 



As compared with Table I, Table II shows a greater 

 variation in the offspring— the classes light brown and 

 yellow brown make their appearance and comprise jnst 

 50 per cent, of the offspring, a result that accords with 

 the hypothesis that light brown is heterozygous and flaxen 

 or light yellow is recessive, for, DR X RR is expected 

 to yield 50 per cent, of the DR (light brown) type. We 

 note here as in Table I that the hair is in no case darker 

 in the children than in the darker parent ; but it may be 

 less dark. 



Table ITT. Distribution of Hair Color in the Offspring when Both 



Assuming two cases of ' 'auburn brown" in Byr family 

 to be essentially golden brown (this hair has not been 

 seen by us) it appears that when both parents have light 

 brown hair either all of the children are of the same type 

 (Pla-B, Ste-G, Tuc. families) or else of the light brown 

 and lighter (yellow brown to flaxen-Byrf, Klo. family). 

 In the first case the parents act like homozygous domi- 

 inants toward the lighter types; in the second case like 

 heterozygous dominants. 



In this case we obtain a total of 42 offspring, 16, or d» 

 Per cent., dark brown and brown, and 26, or 62 per cen ., 

 light brown or lighter. Taking dark brown as hetero- 



