48 



Mutability and Individual Variation. 



tions are of an entirely different nature from the rest 

 of the phenomena included under the name of variability. 

 They have this in common that they are always present 

 and can be observed every year and in every group of 



2 23 /ns 167 ;o6 33 



' Fig. 10. Curve of Beans/ 



individuals provided it is not too small. They are always 

 grouped round a mean, and the numbers of the deviations 



cording to Quetelet's law. For a more exact demonstration a cor- 

 rection would be necessary, since obviously the larger beans fill up 

 their compartment more than a similar number of small ones. 



^ Curve of the red-spotted beans. The curve is plotted from the 

 observations reproduced in Fig. 9. It corresponds to the theoretical 

 form (a-f^)" sufficiently exactly, as is evident by mere inspection. 

 The length of the ordinates is proportional and almost equal to the 

 corrected height of the groups of beans belonging to each compart- 

 ment of the glass case. The number of beans found in each com- 

 partment is found at the foot of the corresponding ordinate. A bean 

 from each group is drawn as a sample to show the extent of fluc- 

 tuating variability in length. The beans are seen to be very variable 

 in form and coloring also. 



