448 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1921. 



generation of the mixed progeny may, through a Mendelian form of 

 heredity, be born once more pure light, medium, or dark, as were their 

 parents or grandparents, is not yet definitely known, but the plainly 

 evident results of the mixture between different types of pigmen- 

 tation is a large variety of intermediaries. 



The effects of such mixtures are not manifested in the same way 

 in all the involved parts. The skin-hair-eye pigmentation behaves in 

 a large measure as a unit, but in interbreeding not infrequently this 

 complex becomes more or less dissociated and its components enter 

 into differing combinations with the pigmentation factors provided 

 by the other germ cell. The skin, hair, and eyes show somewhat 

 different tendencies in these directions. 



In the skin the usual result of a mixture of two types of color is a 

 uniform change, but the grade of this change may show considerable 

 differences in different members of the resulting family. There are, 

 however, also cases of irregular " blends." These may be witnessed 

 occasionally in the admixtures of the white with the negro, and, 

 probably more frequently than we are generally aware of, in the 

 mixtures of darks and lights among the white people. The darker 

 strain manifests itself in the form of more or less marked irregular 

 areas or patches, or in larger or smaller "freckles." Permanent 

 freckles have much more significance than they have hitherto re- 

 ceived, and even passing freckles may occasionally have a phy- 

 logenetic rather than mere ontogenetic or casual significance. The 

 characteristic freckled " Scotch skin " is much more probably a 

 record of admixture of a darker with a light type in the past, than a 

 sun effect, or a meaningless individual, or tribal peculiarity. 



The hair in mixture behaves much like the skin. Generally the 

 result is a " blend," or rather increased pigmentation more or less 

 over that of the lighter parent. But not infrequently in mixed 

 progeny with the lighter shades of hair, particularly in females 

 where due to the length of the hair the conditions may be more easily 

 appreciated, there may be detected strands of darker or lighter hair 

 than the majority. xVn imperfect blend seems also to exist in some 

 of the " sandy " or " rusty " reds. Individual tufts or locks of black 

 or white hair are anomalies, though they may run in families. 



The organs in which the most varied and interesting conditions 

 result in consequence of mixture are, however, the eyes. The original 

 human eye was probably hazel (or medium brown) to dark brown. 

 All the primates, all the colored races of man, and a considerable 

 proportion as yet of the whites have brown eyes. Such eyes in earlier 

 times were doubtless associated with dark hair as well as a darker 

 skin. But under the already discussed environmental conditions of 

 northwestern Europe, acting through thousands of years, the pro- 

 tective brown pigment, no longer needed, was eliminated until it 



