152 Scientific Proceedings, Royal Dublin Society. 
those organisms which, having accomplished the reproductive act, 
almost immediately expire. This view of nature is very repel- 
lent to us who reflect and are self-conscious. But it is, never- 
theless, evident that we are but parts of an economical system 
which ruthlessly sacrifices the individual on general grounds of 
economy. ‘Thus, if, in the life history of any individual organism, 
the (imaginary) curve which defines the mean rate of reception of 
energy at different periods of life be opposed by a second curve 
Energy 
Time 
drawn below the axis along which time is measured, representing 
the mean rate of expenditure of energy (see fig.), this curve must 
be of such a nature from its origin to its completion in death, when 
there is no further expenditure of energy except in the post- 
vital disintegration of the body, that the condition is realized 
of the most economical rate of expenditure at each period of life.* 
The rate of expenditure of energy at any period of life is, of course, 
in such a curve defined by the slope of the curve towards the axis 
of time at the period in question; but this particular slope must 
be led to by a previous part of the curve, and involves its past 
and future course to a very great extent. There will, there- 
fore be impressed upon the organism by the factors of evolution 
a unified course of economical expenditure completed only by its 
death, and which will give to the developmental progress of the 
individual its prophetic character. 
In this way we philosophically look to the unified career of 
each organic unit, from its commencement in the ovum to the 
1 See “‘ The abundance of Life,’’ these Proceedings, ante, Vol. vu, p. 78. 
