18 



HELEN DEAN KING AND HENRY H. DONALDSON 



for comparison with the findings in later generations to indi- 

 cate the changes in the rate and in the extent of body growth 

 that resulted from life in captivity. 



Weight changes in the body with age for individuals in the 

 first group, comprising the second to the fourth generations, 

 inclusive, are shown in table 1. 



TABLE 1 



Showing the increase in the weight of the body with age for individuals in the 

 second to the fourth generations of captive gray rats 



In the first group, as indicated by corresponding entries 

 for the two sexes in table 1, the average weight of the males 

 at thirteen days of age was only slightly greater than that of 

 the females. At later age periods the excess in favor of the 

 males increased greatly. 



