78 



Scientific Proceedings, Royal Dublin Society. 



particle as origin, its propagation involves a continual accelerated 

 inflow of energy from the surrounding medium, a dynamic condi- 

 tion unknown in periodic effects, transmitted by inanimate actions, 

 and, indeed, marking the fundamental difference between the 

 dynamic attitudes of the animate and inanimate. 



We can trace the periodic succession of individuals on a diagram 

 of activity with some advantage. Considering, first, the case of 

 the unicellular organism reproducing by subdivision and recalling 

 that conditions, definite and inevitable, oppose a limit to the rate of 

 growth, or, for our present purpose, rate of consumption of energy, 

 we proceed as follows : — 



i , Time. 



Fig. I. Lifer Waves of the Amceba. 



Along a horizontal axis units of time are measured ; along a 



vertical axis units of energy. Then the life-history of the ameeba, 



for example, appears as a line such as A in fig. 1. This line 



starts at the point of origin of the axes of reference. During 



the earlier stages of its growth the rate of absorption of energy is 



small ; so that in the unit interval of time, t, the small quantity of 



energy, ei, is absorbed. As life advances, the rate of activity of 



the organism augments, till finally this rate attains a maximum, 



when ^2 units of energy are consumed in the unit of time. At 



de . 

 any moment of its life, the rate of activity, — , is represented by 



the trigonometrical tangent of the angle made with the axis of 

 time by aline tangential to the curve at the point in question. 



