64 HEREDITY AND EUGENICS 



Although albino mutations occur in black races, the 

 ' white " man is by no means devoid of pigmentation. 

 It appears probable that man}^ small germinal changes 

 affecting pigmentation were involved. The known 

 relations between skin pigmentation and the adrenal 

 capsules indicate that germinal changes which 

 affected the activity of these glands were really in- 

 volved. From recent studies of the endocrine gland 

 secretions, it appears that differences in the activities 

 of various endocrine glands are responsible not only 

 for the differences in pigmentation of the various 

 races of mankind, but also for their characteristic 

 physiognomies (see p. 211 ff.). 



In the same way, it is highly probable that brown 

 w^as the primitive eye colour in man, and that blue 

 arose from it through one or more mutations, with 

 loss of pigment. (For a further discussion of this 

 subject see p. 44.) It may be that blue arose origin- 

 ally as a simple mutation from brown, and that 

 intermediate shades have come in later. This has 

 been shown to be the history of various cases of 

 melanism in Lepidoptera. But at present there is 

 no definite evidence to prove the point either way as 

 regards man. When blue e3'es were once established^ 

 they multiplied in the northern races, perhaps through 

 sexual selection, until blue eyes are characteristic of 

 the Scandinavian and other northern peoples. But 

 the native peoples in tropical countries appear always 

 to have retained brown e3^es, the pigment probably 

 being a protection for the e3^e against the strong rays 

 of the sun. The white race is thus in a sense an 

 albinotic variation, which has arisen through loss of 

 pigmentation. This loss has been carried still further 

 in the more northern races with fair complexion, 

 light hair, and blue e3^es. 



In the Pearson monograph on albinism many early 

 records of albinotics are considered. It is concluded 



