Man 159 



discretion, and discretion requires mental 

 power. 



The names of the intellectually eminent 

 men selected for investigation, and the de- 

 tails of their pedigrees as far as known, were 

 given in Control of Heredity. Here we will 

 give the general results with a few additional 

 facts learned since 1902. These facts show 

 generally that the men of great intellectual 

 power were sons of old or comparatively old 

 fathers, and that the grade of intellect, from 

 the top to the bottom of the scale, was 

 approximately proportional to the age of the 

 father at the birth of the son. Of course it is 

 not possible to grade these intellectual giants 

 with respect to each other, still, by dividing 

 them into fair-sized groups by the ages of 

 their fathers, it could be distinctly seen that 

 the groups represented a graduated scale. 

 The intellectual grade of the children repre- 

 sented the intellectual grade of the parents 

 at the time the children were conceived. 



In the case of horses it was pointed out that 

 we sometimes get a 2 : 10 stallion from a 



