I. LIFE PROCESSES .'II 



a straight line, as these females showed no pronounced ac- 

 celeration in body growth during early postnatal life. Graph 

 2, for gray females of the tenth generation, runs higher than 

 graph 1 from its beginning until the end of its course. At tin 

 150-day period the space between these graphs represent > a 

 difference of 44 grams, or 31 per cent, in average In Mix- 

 weights. Subsequently these graphs run much closer, and 

 their position at the end of the weighing period indiran - a 

 difference of but 8.1 per cent in the average body weights. 



Albino females show the same marked acceleration in 

 growth during the first growth phase as do albino males. In 

 chart 5, as in chart 4, the graph (3) for Albinos runs much 

 higher during the early part of its course than either of tin- 

 graphs for Grays. At a later period, however, graph ." 

 flattens and falls below the level of the other graphs, since 

 the albino females were not as heavy as ^ray females during 

 adult life. 



At 150 days of age albino females had an average bod\ 

 weight that was 44 grams, or 23.fi per cent, heavier than that 

 of gray females of the first generation. At this age, however, 

 gray females of the tenth generation had the same weight as 

 that of the albino females, and they were much heavier in 

 later life (chart 5). 



The change in the rate and in the extent of body growth 

 that had occurred in gray females at the end of ten trenera- 

 tions of life in captivity was similar to that in the males. 

 The trend was toward the type characteristic for albino rats 

 in general. In only one series of Albinos for which data are 

 available, that of Greenman and Duh ring ( '23), does the body 

 weight of adult animals equal that of the tenth generation of 

 captive Grays. These Albinos, however, were given exowiae 

 and were especially well cared for and fed. 



The findings in these captive Grays are in accord with th<i 

 for various domesticated animals, such as cattle, >h-rp, 

 horses, etc., which are much larger at all age periods than 

 their wild prototypes. 



