466 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1921. 



again, no serious attempt lias yet been made at showing the reason. 

 Yet there must be reasons, and judging from the generality of the 

 tendency, they are more likely to be of inherited than of environ- 

 mental nature. 



These are the facts that may have a bearing on this question. In 

 the section on skin pigmentation it was seen that the skin of the 

 male is more frequently darker than medium than happens among 

 the females; should this fact be substantiated elsewhere, we would 

 be justified in assuming that the skin in the male takes care on the 

 average of a somewhat larger quantity of the pigment produced in 

 the body, while in the female, should she produce proportionately 

 to her weight as much pigment as man, the surplus would be likely 

 to go into the eyes and hair. In addition, the male discharges a sub- 

 stantial quantum of pigment through his beard, moustache, and 

 greater body hairiness, as well as through the hair of the head, for 

 due to the frequent cuttings a man produces on the average more hair 

 on his head than a female. All this disposes in the male of a consid- 

 erable amount of the pigment formed in the body, so that if the sexes 

 produced the same or nearly the same amount per pound of active 

 tissue, there would be a surplus of pigment in the female which 

 would inevitably, it seems, affect the pigmentation of both the eyes 

 and the hair. There is no indication that there is any greater pro- 

 duction of pigment in the female, but she differs slightly in the man- 

 ner of its disposition and elimination. 



The relative pigmentation of eyes in the two sexes may also, as in 

 the case of hair, be presented in the form of values. If the subject 

 is carefully weighed it will be found that about the following ap- 

 proximate values may be assigned to the different eye colors : 



Assumed values of eye colors. 

 Pure lights: 

 Blues- 

 Light 10 



Medium 20 



Deep 25 



Greenish 15 



Gray 30 



Mixed 50 



Pure browns: 



Light 65 



Medium 75 



Dark 85 



Arranging our data on this basis, we obtain the following inter- 

 esting results : 



