Of course this is no place for a lecture on methodology, and it therefore must suffice to make one remark with special regard to our purpose, which we should like to emphasise. Our concept of the harmonious-equipotential system--say rather, our concept of the prospective potency itself--presumes the understanding that indeed *all* blastomeres and *all* stems of *Tubularia*, including those upon which we have *not* carried out our experiments, will behave like those we have experimented with; and those concepts also presume that a certain germ of Echinus, *A*, the blastomeres of which were not separated, would have given two whole larvae, if separation had taken place, while another germ, *B*, which actually gave us two larvae after separation, would only have given one without it. Without this presumption the concept of “potency” is meaningless, and, indeed, every assumption of a “faculty” or a “possibility” would be meaningless in the whole area of science. But this presumption can never be proved; it can only be postulated. It therefore is only with this postulate that our first proof of vitalism holds; but this restriction applies to *every* law of nature. I cannot force you to agree with this postulate: but if you decline you are practically saying that there exists a sort of pre-established harmony between the scientific object and the scientist, the scientist always getting into his hands such objects only as have been predestinated from the very beginning to develop two larvae instead of one, and so on. Of course, if that is so, no proof of natural laws is possible at all; but nature under such views would seem to be really dæmonic. And so, I hope, you will grant me the postulate of the universality of scientific concepts--the only “hypothesis” which we need for our argument. 4. ON CERTAIN OTHER FEATURES OF MORPHOGENESIS ADVOCATING ITS AUTONOMY Our next studies on the physiology of form will be devoted in the first place to some additional remarks about our harmonious-equipotential systems themselves, and about some other kinds of morphogenetic “systems” which show a certain sort of relationship with them. For it is of the greatest importance that we should become as familiar as possible with all those facts in the physiology of form upon the analysis of which are to be based almost all of the future theories that we shall have to develop in biology proper and philosophical. Our discussions, so far as they relate to questions of actual fact, will contain only one other topic of the same importance.