4 Ada Springer 



pressed. The same principle holds in case of the rate of star- 

 vation. During a period there is a definite loss, but at the 

 beginning of that period there is more material to lose weight 

 than at the end, so the actual amount of decreasing material will 

 lie as a mean between the first and last weights of the period. 



The rate of increment and loss is best expressed for purposes 

 of comparison in percentages, as absolute increments do not show 

 relations between rates; for example, the absolute increment of a 

 larger individual may be greater than that of a smaller one, yet 

 the rate of growth in both may be the same, or even greater in 

 the small one. This is shown in many of the tables, where the 

 absolute increment and the percentage increment are both given. 

 The percentage was calculated from the average weights of the 

 sets. 



II THE NORMAL RATE OF GROWTH 



Increase in weight in Diemyctylus viridescens is due, as Mr. 

 Morgulis^ has discovered, not to storage of fat in the various parts 

 of the body, but to a uniform increase in the size of many of the 

 organs, e. g., the skin, muscles, liver, ovaries, etc. This type 

 of growth seems, therefore, comparable to growth from a young 

 to an adult stage. Conversely in starvation there is a decrease 

 in the size of the organs. 



Percentage increment decreases as the maximum weight is 

 approached; that is, the rate of growth becomes slower the nearer 

 the animal approaches its upper limit of weight. 



In Set A^ (Table I), where the individuals had been fed 153 

 mg. (average) of the beef a week, there was a tendency for 

 the percentage increment of weight to decrease as the animal 

 approached the maximum or limit of weight. It might be 

 supposed that a stage would be reached where this amount of 

 food proved insufficient to produce an increase, and in conse- 

 quence a state of equilibrium would be established between the 

 body material and the amount of food, around which equilibrium 

 there would be a fluctuation between loss and gain. If now an 



Unpublished work of S. Morgulis. 



