EXPERIMENTAL EVOLUTION 



viduals measured. The length varied from 8 to 16 

 millimeters, and in the following proportions : 



Millimeters 8 9 10 n 12 13 14 15 16 



Number of beans, i 2 23 108 167 106 33 7 i 



The beans were then placed 

 in a glass jar divided into 

 nine compartments, all the 

 beans of the same length 

 in the same compartments. 

 When this was done it was 

 found that the beans were 

 so grouped that the tops of 

 the columns in the various 

 compartments followed a 

 curve, known as Quetelet's 1 

 curve (Fig. 51). 



This curve may be plotted 

 by erecting vertical lines 

 (ordinates) at intervals of one 

 millimeter on a horizontal 

 line or base, the height of 

 each vertical line being pro- 

 portionate to the number of 

 beans having the length in- FlG ^.-Demonstration of 



dicated in figures at its base. Que"telet's law of fluctuating varia- 



This curve shows the freq- bilit >' in the len & th of seeds of * he 

 , .. common bean (Phaseolus videaris). 



uency of occurrence of seeds Description in the text . (Redrawn 

 of any given dimension from de Vries.) 



1 So named from its discoverer, QuStelet (Ket-lay). As de Vries states: 

 "For a more exact demonstration a correction would be necessary, since 

 obviously the larger beans fill up their compartment more than a similar 

 number of small ones." 



