Only the mature determinant is able to develop, especially if, at the same time, a related and heretofore active determinant must be forced back into the latent condition. But the determinant of an absolutely new form of adaptation, which does not take the place of a preceding one, must develop enough before it can become outwardly manifest, for it to be possessed of a sufficient amount of molecular energy to render its activity possible. For this reason the characteristics of the developed organism change abruptly, notwithstanding the fact that the transformation of the idioplasm has proceeded very gradually. The configuration of the idioplasm becomes continually more complex through the automatic action of the perfecting process, and by this means the organism ascends to higher stages of organization. Hence the viable determinants of organization or perfection are always overtaken after a certain time by that movement and forced into the latent condition. They then become continually weaker, and are at last completely destroyed. Only in the first period after their becoming latent can such determinants pass again into a developmental condition and thus allow the organism to revert to the next preceding stage of organization. Since the configuration of the idioplasm, which becomes more complex from internal causes, always assumes a definite character of adaptation in consequence of the action of external causes, the adaptation determinants capable of development may become more and more weakened and at last latent when other external causes produce other adaptation determinants. But these determinants may be revived by the renewed activity of the former causes, and thus rendered capable of development. Hence the organism may show the most various reversions with respect to its adaptations. But in such reversions the earlier forms never quite return, because in the meanwhile the idioplasm has changed somewhat in consequence of its automatic progress, and therefore lends to the adaptations which assume the earlier character a somewhat different expression. 13. ONTOGENETIC DEVELOPMENT OF THE DETERMINANTS. Since the capability of the primordial plasma to grow is the original and only vital quality (_Anlage_), the whole ontogeny in this first stage consists in the growth of the detached parts to the adult size. In the same way the development of the determinants in all the following stages is nothing more than the growth of the substance detached as a germ cell after the manner of the changes in the character of the idioplasm in the course of phylogeny. In this manner all determinants may in the lower stages of organization reach development, but in the higher stages an increasing number of them must remain latent.