r,so 



THE AMERICAN NATURALIST 



[Vol. L 



No. 2 is the mean of the population. Curve No. 3 is the 

 plus deviation from the mean. Curve No. 4 is a curve 



Co rises of M//A- Proc/(/c/-/o/7 -r~/$.Z 



which was plotted to show what the requirements ought 

 to be if the means, deviations and varying capacity of the 

 different classes are taken into account. In plotting this 

 curve it was necessary to consider the basis upon which 

 the minimum requirements of this population ought to 

 be placed. 



The minus deviation point can not show what ought to 

 be required of the class as a minimum, for such point 

 would weight individuals inversely in proportion to their 

 capacity. A greater deviation from the mean of the class 



