26 



HELEN DEAN KING AND HENRY H. DONALDSON 



2 at the 180-day period indicates a difference of 39 grams, 

 or 19.9 per cent, in the body weights of these two series of 

 males. At the end of the weighing period (608 days), the 

 position of the graphs indicates a difference of 4.1 per cent 

 in the body weights. 



TABLE 4 



Showing the increase in the weight of the body with age and the coefficients 



of variation for males in the first and in the tenth generation of captive gray 



rats, also coefficients for a series of stock albino males 



The graph (3) for stock albino males has a distinctly dif- 

 ferent form from that of either of the graphs for gray males. 

 At the age period from 40 to 150 days the graph has a very 

 pronounced upward curve. Subsequently it flattens, and runs 



