VARIATION AND HEREDITY 17 



plexity to a higher, but the reverse may be true. 14 Thus 

 experimental breeding has shown that the white coat of 

 the horse is not a simple character, but is due to several 

 independently inheritable factors. 15 



Besides the Mendelian theory of inheritance there is 

 one other theory: Francis Galton's theory of Regression. 

 The theory as first expounded was based upon the meas- 

 urements of the stature of over 900 English individuals. 16 

 Galton found that the form of the body of an individual 

 is determined by the racial type to which the parents 

 belong, modified, however, by a tendency of reversion to 

 a type intermediate between the special variations pre- 

 sented by the parents. For example, if the father of an 

 individual is exceedingly tall, and his mother somewhat 

 taller than the average, it is often found that the children 

 tend to develop a stature which is somewhat near the 

 general type, but at the same time dependent upon the 

 intermediate value located between the stature of the 

 mother and that of the father. In accordance with this 

 theory it was found that the influence upon the individual 

 of inheritance was about y from each parent and VIG 

 from each grandparent. This law of regression was 

 found to hold for the inheritance of stature, eye-color, 

 and artistic ability. More recent studies have shown 

 that the intensity of heredity for each parent may be 

 expressed by about one-third. 17 The principle of regres- 

 sion may be made clearer by quoting from Professor 

 Boas: " Provided the mother differs in her stature by an 

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



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



is Davenport, f>p. cit., p. 24. m Galton, op. cit., chs. vi. and vii. 



if Pearson, K. "On the Laws of Heredity in Man," Biometrika, vol. ii, 

 p. 357 et scq.; and Boas, F. "Heredity in Anthropometric Traits," Amer. 

 Anthropologist, N. S., vol. ix, p. 453 et seq. 



