VARIATION AND HEREDITY 17 



plexity to a Iiiglior, ))ul llic rcvc'i-sc iiiny Kc line.'* Thus 

 experimental breeding has sliown tliat the wliite coat of 

 the horse is not a sinipk' character, but is due to several 

 independently inheritable factors.'^ 



Besides Mendel's Law, there are Galton's two statis- 

 tical laws of inheritance: the Law of Regression and the 

 Law of Ancestral Inheritance. The Law of Regression 

 as first expounded was based upon measurements of the 

 stature of over 900 English persons.^" Galton found 

 tlmt the stature of an individual is determined by the 

 racial type to which the parents belong, modified, how- 

 ever, by a tendency to revert to a type intermediate be- 

 tween the special variations represented by the parents. 

 For example, if the father is very tall, and the mother 

 somewhat tailor than the average, the childi-en tend to 

 develop a stature which is somewhat near the racial 

 ty]K', l)ut at the same time dependent upon an inter- 

 mediate value located between the stature of the mother 

 and that of the father. This law a])i)eared to hold for 

 the inheritance of stature, eye-color, and artistic ability. 

 1 biologists have criticized Galton's laws on the ground 

 tliat they lump together both inherited and non-inherited 

 \ariations. The Law of Ancestral Inheritance showed 

 tliat on the average each parent contributes i/4 of every 

 inherited faculty, each grandparent Vu-,, and so on. 

 j\rore recent studies have shown that the intensity of 

 heredity for each parent may be expressed by about ]-\.^' 

 The principle may be made clear by quoting from Or. 

 Boas : ' * Provided the mother differs in her stature by an 

 amount of 9 em. from the racial norm, — for instance, if 



1* Thomson & Geddes, op. cit.. p. 137. 



i'> Davonport, op. rif., p. 24. "■■ Calton, ap. rit.. vh-i. vi. and vii. 



"Pearson, K. — "On the Laws of TToredity in Man." Bionirtrika, vol. ii, 

 p. 357 ct sc(i.; and Boas, F. — "Ileiodity in Anthropometric Traits," Ainer. 

 A)ithropoJo(iist, X. S., vol. i\, ]). 4ri3 ct seq. 



