No. 508] HEREDITY OF HAIR COLOR IN MAN 



211 



of the children, the character in question would probably 

 become quite degenerate. Since the note in Science was 

 published we have read a paper by Feer, to which our 

 attention was called by the title "Der Einfluss der Blut- 

 verwandschaft der Eltern auf die Kinder." 4 This paper 

 comes very near to our point of view. After showing 

 that retinitis pigmentosa and congenital deaf -dumbness 

 are the diseases most closely associated with inbreeding 

 the author concludes that they are not so much inheritable 

 diseases in the usual sense as inheritable diseases of 

 degeneration, and depend on degeneration of the em- 

 bryonic ectoderm. It seems clear from such data as Feer 

 adduces that our general thesis will hold true for many 

 human characters— that inbreeding does not cause them 

 to degenerate, but having a tendency to degenerate, in- 

 breeding will prevent any recovery and, in addition, will 

 hasten the downward tendency from generation to gen- 

 eration. The only way to avoid progressive degeneration 

 is to bring in (usually necessarily from outside) blood 

 with the tendency to produce the characteristic in a well- 

 developed condition. 



Combining now the results of the three studies on eye 

 color and hair color and form made by us, 5 it appears that 

 two parents with clear blue eyes and yellow or flaxen 

 straight hair can have children only of the same type, no 

 matter what the grandparental characteristics were; that 

 dark eyed and haired, curly-haired parents may have 

 children like themselves but also of the less developed 

 condition. In the latter case what the proportions of 

 each type will be is, for a fairly large family, predictable 

 by a study of the immediate ancestry. 



Carnegie Institution of Washington, 



Department of Experimental Evolution, 

 Cold Spring Harbor, N. Y., 

 December 1, 1908. 



4 Separate, Berlin, 1907; also " Jahrbuch fur Kinderheilkunde, " Bd. 

 LXVI. 



5 G. C. and C. B. Davenport, "Heredity of Eye-Color in Man," Science, 

 N. S., XXVI, pp. 589-592, November 1, 1907; "Heredity of Hair-Form 

 •in Man," American Naturalist, XLII, pp. 341-349, May, 1908. 



