e, greater or less variations, which constitute
_nutrition varieties_, and since the idioplasm remains unaffected in
general, last only so long as the causes which called them forth.[F]

[F] Naegeli, like Weismann, arrives at the conclusion that
acquired characters are not inherited. He was not content,
however, to rest the generalization upon purely speculative
grounds, but undertook the experimental demonstration. After
seventeen years of work by himself and son, especially upon
several species of Hieracium, he satisfied himself that his
theory was true to the facts. We all know now how far he fell
short of settling the question.--_Trans._

If we have in mind the inner nature of the organism, there is, properly
speaking, no such specific phenomenon as heredity, since the
phylogenetic line is a continuous idioplasmic individual. In this sense
heredity is nothing more than the persistence of organized substance in
a movement in which variations are automatically induced, or the
necessary transition of one idioplasmic configuration into the next
following. It is present, not only among plant and animal individuals
which are ontogenetically separated, but also everywhere within these
individuals, where individual parts (cells, organs) follow each other in
time. Hereditary phenomena are those that necessarily pass over to
following generations, and in general those that are located in the
idioplasm, since non-idioplasmic substance can be hereditary only
through a limited number of cell generations.

Variations and heredity are generally estimated, not according to the
inner nature of the mature individuals, but according to their relation
in successive generations, since heredity is assumed when the
ontogenetic characters remain the same, and variation when previously
latent characters become visible. But these phenomena belong to another
department of science; they concern the possibility and reality of
development of the idioplasmic determinants.

17. VARIETY, RACE, MODIFICATION.

From the multifarious variations of organisms proceed various categories
of kinship. _Varieties_ arise by extremely slow changes in the idioplasm
due to the perfecting process and adaptation. Since these are
conditioned by the same causes, they follow in all individuals of the
same variety in uniform manner. Varieties are uniform, entirely constant
under the most various external conditions, in general cro