526 



EVOLUTION 



470, in which case beans are assorted according to size. Of course 

 where size is the variation considered, the space occupied by 

 each class of individuals will vary more than the number of 

 individuals in each class, for the smaller individuals occupy less 



FIG. 469. Quetelet's law of continuous or fluctuating variability, demon- 

 strated by arranging 82 ears of Corn in piles according to size. The ears were 

 taken from unselected material from a field of Corn. The length and number 

 of ears in each pile are given in figures below. Notice that the piles decrease 

 each way from the pile (highest pile) containing the ears of average length, 

 decreasing accordingly as the length of ears in each pile is greater or less than 

 the average length. After Blakeslee. 



^y 



FIG. 470. A demonstration of Quetelet's law of continuous variation in 

 the size of the seeds of a Common Bean. The seeds are grouped with refer- 

 ence to length. The longest column contains those of average length and 

 the columns to the right or left of it are shorter accordingly as the length of 

 Beans in each column are greater or less than the average length. Redrawn 

 from De Vries. 



space than the larger ones. All kinds of continuous variations, 

 such as number of flowers per plant, number of seeds per pod, 

 weight of seeds, height of plant, size and shape of leaves, etc., 

 distribute themselves around an average in the same general way 

 as illustrated by size in case of Beans and ears of Corn. 



