38 



HELEN DEAN KING 



have influenced them. Data for sex distribution and for sex 

 ratios in rats of later generations are given in table 11. 



The sex ratios in table 11 are discordant, and do not show 

 any definite trend as the generations advanced. In many 

 cases a high ratio in one generation is followed by a relatively 

 low ratio in the succeeding generation, and there are no sig- 

 nificant differences between ratios for successive generations 



TABLE 11 



Sex distribution and sex ratios in the eleventh to the twenty-sixth generation of 



captive gray rats 



nor between any one ratio and that for the series as a whole. 

 The ratio for individuals in the eleventh to the twenty-sixth 

 generations is but slightly higher than that for the first ten 

 generations, and for the combined series is below equality, 

 being 97.3 males to 100 females. 



Figure 12 shows graphically the sex ratios for the first 

 twenty-six generations of captive grays. 



