34 HEREDITY [ch. 



character which varies continuously about a mean or 

 mode, the greater the divergence from the mode in 

 either direction, the fewer will be the individuals 

 showing that divergence. In the case of human 

 stature, if the modal height of a population is 68 

 inches, there will be fewer men of 64 or 72 inches 

 than of 66 or 70, and still fewer of 63 or 73 inches. 

 If now the sons of all the men having a given diver- 

 gence were measured, and it were found that they 

 averaged as gi'eat a divergence from the mode as 

 their fathers, it is clear that on the average the 

 height of the sons would equal that of their fathers. 

 This does not mean that every son would exactly 

 resemble his father in stature, but the sons would 

 vary about the paternal stature equally above and 

 below it, and when plotted in a curve their statures 

 would make a curve having the paternal stature as 

 its mode. The average stature of the sons would 

 then be completely determined by the stature of the 

 fathers. If on the other hand the stature of the 

 father had no relation with that of his sons, it is 

 clear that the statures of the sons of fathers of any 

 height would vary about the mean of the general 

 population considered. In practice it is found that 

 the modal value for sons of fathers of a given height 

 is between the height of their fathers and the mode 

 of the general population. That is to say, if the fathers 

 diverge a given amount from the general mode, their 



