472 



EVOLUTION, GENETICS, AND EUGENICS 



exceptional parents tend to be, on the average, one-thircl less exception- 

 al than the parents. This he called the Law of Filial Regression. 



Similar results were obtained with several other types of human 

 differences that were capable of being graded quantitatively and ar- 

 ranged in classes. Thus when eye-colors were graded on the basis 



Fig. 88. — Diagram to illustrate Galton's "Law of Filial Regression" as shown 

 in the stature of parents and children. The mean height of all parents is shown 

 by the dotted line between 68 and 69 inches. The circles through which the diag- 

 onal line runs represent the heights of graded groups of parents, and the arrow- 

 heads indicate the average heights of their children. The offspring of undersized 

 parents are taller and of oversized parents are shorter than their respective parents. 

 {From Conklin, after Walter.) 



of the amount of pigment in the iris and arranged in nine or ten classes, 

 it was found that there was practically the same amount of filial re- 

 gression as there was in the case of stature. This was true for all ex- 

 cept the pure blue-eyed parents, with no pigment in the front of the 

 iris, where no regression in the offspring was noted. Blue-eyed indi- 

 viduals, are, of course, homozygous, if they are really blue-eyed in the 

 genetic sense. 



