28 HELEN DEAN KING AND HENRY H. DONALDSON 



nearly level until its termination at the 480-day period. 

 Graphs might be constructed from available data for various 

 other series of albino males that would, doubtless, have a 

 slightly different course than that of the graph given in chart 

 4, but all such graphs would indicate very rapid growth dur- 

 ing early postnatal life, which is, seemingly, characteristic 

 for the albino race in general. 



The relative positions of the graphs in chart 4 indicate that 

 during the period of rapid growth, from 40 to 150 days, albino 

 males were very much heavier than gray males of either 

 series. At the 150-day period the space between the graph 

 (3) for albino males and the graph (1) for gray males of the 

 first generation represents a difference of 69 grams, or 28.2 

 per cent, if the body weight of the albino males is taken as 

 the standard in computation. At this age period, however, 

 albino males were only 28 grams, or 11.4 per cent, heavier 

 than gray males of the tenth generation. 



From the above analysis of data it is evident that the 

 course of body growth in gray males had changed consider- 

 ably at the end of ten generations of life in captivity. Dur- 

 ing the first growth phase the rate of growth was accelerated 

 and was approaching the albino type. During the second 

 growth phase the chage was relatively slight, since the ulti- 

 mate body weight attained by males of the tenth generation 

 was only about 4 per cent greater than that of the males in 

 the first generation. 



Data for the increase in the weight of the body with age for 

 females in the first and for those in the tenth generation of 

 captive Grays are given in table 5. 



In table 5 the findings for gray females parallel those for 

 the corresponding series of gray males (table 4) in that they 

 show that females of the tenth generation were heavier than 

 females of the first generation at all age periods for which 

 records were taken. 



Chart 5 shows graphs constructed from the average body 

 weights of gray females as given in table 5. In this chart, 

 also, is a graph (3) for the body growth of albino females, 



