372 



ON INCREASE IN SIZE 



[PT. Ill 



distribution is shown by the distance to the right of the vertical base- 

 Hnes, and can be judged by the frequency-scale at the bottom of the 



WEIGHT 

 GRAMS 



1 -000 



•1000 



•0100 



•00100 



•00010 



•00001 



9 10 n 12 13 14 15 

 CONCEPTION AGE 



Fig. 22. 



16 17 18 19 



chart. The means, weighted by the number of individuals in each 

 litter, are shown as dots on the vertical base-lines, and it is through 

 these, of course, that the "normal curve" would be drawn. The 

 continuous curve in the graph is one drawn to a formula which 



