ID Ada Sprmger 



after the first week or two, was about 50 mg., or 153 mg. per week; 

 while in the present series the amount was twice as large. The 

 average weight of each piece was 105 mg., or 315 mg. per week. 

 The feeding in this series was regular from the beginning, which 

 was not the case in the first series. 



A record of each individual was kept, together with the number 

 of pieces of beef consumed, so that at the end of a definite period 

 the amount of food taken by each individual was known. Of 

 course there was a chance for error in cases where the beef was 

 later rejected by the animal. It will be well to state that if a 

 certain individual in a set was not disposed to eat for several 

 periods, the corresponding control individual was not fed at 

 these times; thus keeping the conditions in each set as even as 

 possible. 



I TO WHAT FACTORS ARE DUE IRREGULARITIES IN RATE OF 



GROWTH 



It has been found that animals kept under almost identical 

 conditions of temperature, of food given and of depth of water, 

 varied considerably in the rate of increment. As to the causes of 

 these variations, several questions arose : {a) Does sex account 

 for the variation; do females gain faster than males .^ {h) Does 

 the initial weight of the animal affect the percentage increment ^ 

 (c) Do the periods of moulting affect the rate ? 



(a) Males and females. Two sets, one consisting of ten males, 

 the other of ten females, were placed under identical conditions 

 of temperature and food, October 22. The average amount of 

 beef taken by each individual per week was 315 mg. In respect 

 to feeding, these two sets proved to be the most satisfactory of any 

 during the experiments — for, with the possible exception of once 

 or twice, the feeding was absolutely regular. 



After a period of ten weeks the average percentage increment 

 was as follows: 



Per cent 



Set A (Table XVII), males 29.7 



Set B (Table XVII), females 42.1 



