It is necessary to observe on the fundamental distinction between the growth of the protoplasm and the growth of the crystal. It is common to draw comparison between the two, and to point to metabolism as the chief distinction. But while this is the most obvious distinction the more fundamental one remains in the energy relations of the two with the environment.[1] The growth of the crystal is the result of loss of energy; that of the organism the result of gain of energy. The crystal represents a last position of stable equilibrium assumed by molecules upon a certain loss of kinetic energy, and the formation of the crystal by evaporation and concentration of a liquid does not, in its dynamic aspect, differ much from the precipitation of an amorphous sediment. The organism, on the other hand, represents a more or less unstable condition formed and maintained by inflow of energy; its formation, indeed, often attended with a loss of kinetic energy (fixation of carbon in plants), but, if so, accompanied by [1] It appears exceptional for the crystal line configuration to stand higher in the scale of energy than the amorphous. 74 a more than compensatory increase of potential molecular energy. Thus, between growth in the living world and growth in the dead world, the energy relations with the environment reveal a marked contrast. Again, in the phenomena of combustion, there are certain superficial resemblances which have led to comparison between the two. Here again, however, the attitudes towards the energy of the environment stand very much as + and -. The life absorbs, stores, and spends with economy. The flame only recklessly spends. The property of storage by the organism calls out a further distinction between the course of the two processes. It secures that the chemical activity of the organism can be propagated in a medium in which the supply of energy is discontinuous or localised. The chemical activity of the combustion can, strictly speaking, only be propagated among contiguous particles. I need not dwell on the latter fact; an example of the former is seen in the action of the roots of plants, which will often traverse a barren place or circumvent an obstacle in their search for energy. In this manner roots will find out spots of rich nutriment. Thus there is a dynamic distinction between the progress of the organism and the progress of the combustion, or of the chemical reaction generally. And although there be unstable chemical systems which absorb energy during reaction, these are (dynamically) no more than the expansion of the compressed gas. There is a certain 75 initial capacity in the system for a given quantity of energy; this satisfied, progress ceases. The progress of the organism in time is continual, and goes on from less to greater so long as its development is unconstrained and the supply of energy is unlimited.