The whole of the vegetable world is produced by the osmotic growth of mineral substances, if we except the small amount of organic matter contained in the seeds. The most important problem of synthetic biology is not so much the synthesis of the albuminoids as the reduction of carbonic acid. In nature this reduction is accomplished by the radiant energy of the sun, by the agency of the catalytic action of chlorophyll. {158} The physico-chemical study of osmotic growth is as yet hardly begun; we have but indicated the method, the way is open, and the problems awaiting solution are legion. Only work and ever more work and workers are required. Experiments should be made with substances which are chemically unstable like the albuminoids, substances which readily combine and dissociate again, alternately absorbing and giving up the potential energy which is the essence of life. Experiments should also be made with substances which readily unite or decompose under the influence of water, since hydration and hydrolysis appear to be the dominant mechanism in all vital reaction, as they undoubtedly are in osmotic growth, which consists of an increase of hydration on one side of an osmotic membrane and a diminution on the other side. Life is not a substance but a mechanical phenomenon; it is a dynamic and kinetic transference of energy determined by physico-chemical reactions; and the whole trend of modern research leads to the belief that these reactions are of the same nature as those met with in the organic world. It is the grouping of physical reactions and their mode of association and succession, their harmony in fact, which constitutes life. The problem we have to solve in the synthesis of life is the proper attuning and harmonizing of these physical phenomena, as they exist in living beings, and there should be no absolute impossibility in our some day realizing this harmony in whole or in part. Albert Gaudry says: "I cannot conceive why in determining the connecting links of the animal world the fact that an organic body is formed of such and such elements should be of greater importance than the manner in which these elements are grouped. Descartes regarded extension as the essential property of an organized being; he supposed it to be inert of itself, and that it had the Deity for its motive force. To-day the hypothesis of Descartes has given way to that of Leibnitz, who regards force as the essential property of the living being, the visible and tangible matter being only of secondary importance. If we regard the living being as a force, this force is able to aggregate matter under such and such a form, {159} with such or such a structure, and such or such a chemical essence. It does not seem that the classification depending on differences of substance are any more important than those which depend on differences of form."