It would have been simpler, but it would not have suited Weismann’s conception of nature, to say that the “living machine” differs essentially from other machines in not being a machine at all, or anything in the least like one. No machine constructs itself. No machine can do anything but repeat a certain series of movements, each series exactly similar to the last. What Weismann has described is _not_ a machine, just because it is a living organism. It is surely as true in biology as it is in mechanics that in any purely physical chain of sequences you cannot by any possibility get more out at the end than you put in at the beginning, unless you take it in upon the way. “Development,” writes Weismann, “is an expression of life.”[31] But “life,” again, is merely “a chemico-physical phenomenon.”[32] To say that development is an expression of a chemico-physical phenomenon does not seem a very illuminating or helpful generalization. The fact is that the statement that life is a chemico-physical phenomenon does not take us further towards an understanding of the subject than when we say, what is equally true, that chemical and physical phenomena are a manifestation of life. Life is everywhere. We use it as a convenient term for the energies associated with ‘living’ protoplasm, because we observe that when it is present protoplasmic structures act and react (as in the phenomena of nutrition, for instance) in certain chemico-physical ways, while, if it be absent, the same protoplasm acts in other ways, also chemico-physical, but quite different from the former, and analogous to the ways of minerals and of gases into which dead protoplasm finally resolves itself. The chemico-physical actions and reactions appear in a living plant or animal to be under the direction of a force devoted to the preservation of that particular organism. The smallest atom of organic life includes not only a chemical compound but a chemist. In the mineral world we may say broadly that there is no individuality of parts.[33] With protoplasmic structure, therefore, a stage is reached in the evolution of life which we may rightfully call ‘life’ _par excellence_, but there has been no breach of continuity, and it is highly probable, as Weismann himself suggests, that far below the limits of microscopic observation the transformation of ‘dead’ into ‘living’ matter is continually going forward. When, therefore, we speak of the action of living protoplasm the distinction is rather between this action and that of a piece of mechanism than between protoplasm and minerals or gases.