192 Cc. M. CHILD 
Organisms which meet such conditions are simply eliminated. 
The survival and elimination of organisms is determined primarily, 
not by their morphological characteristics, but by their capacity 
for regulation of one kind or another under the conditions in 
which they find themselves. To attempt to understand the course 
of evolution from morphological characteristics alone can only 
lead to confusion and failure. Only a knowledge of the nature of 
the metabolic current in organisms and the possibilities of its 
equilibration under different conditions can lead to a theoryof 
evolution and heredity which will stand. 
For example, the evolution of animals and plants, like every 
other evolution, is based primarily upon differences in the meta- 
bolic processes. These undoubtedly originated as regulations and 
as soon as they had arisen, gave different possibilities ot further 
regulation: in the course of the realization of these different possi- 
bilities in accordance with the conditionsof existence, animals and 
plants with their different morphological characteristics have 
arisen. In each case the visible structure represents merely a 
partial record of the realized possibilities. All the structural 
‘adaptations’ in both animals and plants are based upon the proc- 
esses of equilibration of the energy current and must sooner or 
later be expressed in terms of this current and its environment. 
They are not the primary and essential features of the organisms, 
they give us merely an outline, a diagram of the most character- 
istic activities of the energy current. As the banks and channel 
of the river, even after the water has ceased to flow, enable us to 
gain some conception, though a very incomplete one, of what the 
river has done in the past, so the structure of the organism is 
merely a rough sketch of what the current of life has done in the 
way of deposition, arrangement and removal of materials along 
its course. Many of the past activities of the current are not dis- 
tinguishable in the structure because their effects were slight or 
transitory, or because they have been masked or altered by later 
activity of a different character. As the river in some process of 
equilibration, e.g., in a flood, a period of increased energy, may 
sweep away many of the records of its previous activity, so the 
