organism, which are the results
of external influences, consist either only of a specific molecular
character (irritability), by virtue of which the individual is capable
of responding to those influences with temporary or permanent phenomena,
or they consist of finished arrangements. The latter have, in general, a
double function: either they protect the organism from external
influences whose results they are, or they place it in a condition to
apply such environmental influences to their advantage. The
preponderance of the one or the other led to the development of the
plant or the animal kingdom. In the one case the primordial plasma
formed in the cellulose cell wall a stimulus-proof covering. On account
of this cell membrane being insensible to stimuli, adaptations in the
plant kingdom were restricted essentially to the spheres of nutrition
and reproduction. In the other case the irritability and mobility of the
primordial plasma increased so that it was placed in a condition to
avoid the irritant or make it serviceable by accommodating itself to it.
The cells sensible to irritants led in the animal kingdom to the
formation of organs of sense and the nervous system.

12. CONDITIONS OF PHYLOGENETIC DEVELOPMENT OF THE DETERMINANTS. ATAVISM.

In the primordial condition, formation and development of the
determinants coincide, since the plasma constituting the organism
possesses the capability of growing by intussusception of new micellae
and of changing this growth through the action of inner and outer
causes. But as the primordial plasma differentiates into idioplasm and
soma-plasm, the formation of determinants consists in the transformation
of the idioplasm, while the development of determinants consists in the
production of soma-plasm and of non-plasmic substances under the
influence of the idioplasm.

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.