150 THE FIRST PRINCIPLES OF HEREDITY 



line we get the number of individuals having the stature 

 of 68 inches — i.e., about 670. Vice versa, if we draw a line 

 parallel to the base line from this same point, it wiU cut 

 the curve at C. A perpendicular from C on to the base 

 line will go through the point marked 68 inches, indicating 

 thereby that 670 individuals out of the whole number 

 possess that height. 



But the Normal Frequency Curve gives us more informa- 

 tion still. The line drawn vertically from the highest 

 point of the curve on to the base line gives us the " Mode " 



7 S B iO II IZ 13 14- IS J6 IT 



Fig. 68. — Curves of Poppies. 

 [From Karl Pearson, " The Grammar of Science.") 



of the variations — i.e., that variation which is possessed 

 by the greatest number of individuals in Fig. 67 repre- 

 sented by the vertical M. The line which divides into 

 equal halves the area enclosed by the curve is called the 

 " Median," and the variation indicated at the foot of the 

 median on the base line gives us the " Mean" or "Average " 

 of all the variations from which the curve is constructed — 

 — i.e., half the number of individuals measured have more 

 and half the number have less than the mean variation. 



In Fig. 68 are represented, according to Professor Karl 

 Pearson, the curves for the number of stigmatic bands 



