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.

Among the viable determinants there are some that develop
unconditionally during each ontogenetic period; there are also
alternative determinants of which one or the other unconditionally
develops; lastly, there are some that develop only under favorable
circumstances. Which of two alternative determinants