23 



108 



167 



106 



33 



FIG. 231. Variation in size of similar units 



On measuring the length of each of several hundred beans taken at random from a 

 large lot, it was found that the largest was about twice as long as the smallest. The 

 number of seeds of each size is shown by the relative height of the corresponding 

 column above the horizontal line. Studies of this kind, repeated by many workers 

 on many kinds of material, show not only that individuals vary, but that they vary 



in a certain way 



