find themselves unable to form these complex combinations directly from their elements; but they succeed in forming them indirectly, by successive modifications of simple combinations. In some binary compounds, one element of which is present in several equivalents, a change is made by substituting for one of these equivalents an equivalent of some other element; so producing a ternary compound. Then another of the equivalents is replaced, and so on. For instance, beginning with ammonia, NH3, a higher form is obtained by replacing one of the atoms of Hydrogen by an atom of Methyl, so producing Methyl-Amine, N(CH3H2); and then, under the further action of Methyl, ending in a further substitution, there is reached the still more compound substance, dimethyl-amine, N(CH3)(CH3)H. And in this manner highly complex substances are built up. * * * * The progress toward higher types of organic molecules is effected by modification upon modification; as through Evolution in general. Each of these modifications is a change of the molecule into equilibrium with its environment—an adaptation, as it were, to new surrounding conditions to which it is subjected; as through Evolution in general. Larger or more integrated aggregates are successively generated; as through
