82 



HELEN DEAN KING AND HENRY H. DONALDSON 



sex in each generation. In a general way, these graphs for 

 the extremes follow those for their respective means. They 

 show also that in the case of the males a deficiency of 15 per 

 cent or more occurs five times, while in the case of the females 

 a deficiency of 14 per cent or more occurs three times. Thus, 

 some individuals do deviate as much as do the Albinos on the 

 average, but, as the results show, these extreme deficiencies 

 have not sufficient frequency to produce more than a slight 

 average deficiency in the case of the captive Grays. 



MALES 



% G, 



HO 



G 2 



Norwoy 



Stondord 



-5 



-10 



-15 



-20 



\ 



Bel 



Chart 15 Brain weight: Deviations of limiting values above and below the 

 mean in each generation of captive Grays. Males. 



Parts of the brain 



The percentages of the brain weight represented by the 

 olfactory bulbs and by the paraflocculi are given in table 15 

 and chart 14. The relations of these percentages can be briefly 

 stated. In both instances the average of the percentage 

 values for the female runs a trifle below that for the male, but 

 in both sexes and for both parts these values remain nearly 

 constant from GX to Gr 10 . It follows from this that the fluctua- 

 tions in the weight of the entire brain are accompanied by 

 corresponding fluctuations in the weights of these parts, thus 

 maintaining constant weight relations. 



