The prospective potency of our system, that is to say of each of its elements, is the sum total of what can be done by all; but the fact that a typically proportionate development occurs in every possible case, proves that this sum comes into account, not merely as a sum, but as a sort of order: we may call this order the “relation of localities in the absolutely normal case.” If we keep in mind that the term “prospective potency” is always to contain this order, or, as we may also call it, this “relative proportionality,” which, indeed, was the reason for calling our systems “harmonious,” then we may apply it without further explanation in order to signify the *non-variable* factor on which the prospective value of any element of our systems depends, and, if we denote the prospective potency, embracing order, by the letter *E*, we are now able to complete our formula by saying *p.v. (X) = f(s, l, E)*. So far the merely analytical study of the differentiation of harmonious-equipotential systems.[59] [59] A far more thorough analysis of this differentiation has been attempted in my paper, “Die Localisation morphogenetischer Vorgänge. Ein Beweis vitalistischen Geschehens,” Leipzig, 1899. *Instances of “Harmonious-Equipotential Systems”* We must try at first to learn a few more positive facts about our systems, in order that we may know how important is the part which they play in the whole animal kingdom, and in order that our rather abstract analysis may become a little more familiar to us. We know already that many of the elementary morphogenetic organs have been really proved to be harmonious-equipotential systems, and that the same probably is true of many others; we also know that the immature egg of almost all animals belongs to this type, even if a fixed determination of its parts may be established just after maturation. Moreover, we said, when speaking about some new discoveries on form-restitution, that there are many cases in which the processes of restitution do not proceed from single localities, the seat of complex potencies in the organism, but in which each *single* part of the truncated organism left by the operation has to perform one *single* act of restoration, the full restitution being the result of the totality of all. These cases must now be submitted to a full analysis.