ith infinite degrees and variations, for it is only a matter
of more or less accentuated averages. In my own face the two halves
are distinctly different, one resembling my maternal ancestry and the
other, in a lesser degree, my paternal ancestry, these points being
seen distinctly in photographs taken in profile.

Each germinal cell contains the hereditary mneme of its ancestors,
paternal and maternal, and the two cells united by conjugation (Fig.
17) that of the ancestors of each of them. We have spoken above of
ecphorias produced according to _Mendel's_ law and reproducing
characters which have been latent during one or two generations.
Darwin was the first to study this interesting fact, which shows how
atavism often results from the crossing of varieties. There are
several varieties of fowls which do not brood; if two of these
varieties, B and C, are crossed excellent brooders are obtained.
_Semon_ assumes that in each of the non-brooding varieties the
ancestral energy, A, of the primary species, is weaker than that of
varieties B and C; we have then A > B, and A < C. But if B is coupled
with A the product represents the value B + C + A + A. Then B and C
are in equilibrium; and A being doubled becomes stronger than each of
them and arrives at ecphoria in their place, which restores the
faculty of brooding to the product of crossing.

_De Vries_ has shown, in the crossing of varieties with their primary
species, more or less analogous phenomena which he calls
"Vicino-variations." Conjugation leads to infinite combinations and
variations which the law of heredity traverses like a guiding line.

The celebrated zoologist, _Weismann_, considers that the chromatin of
each germinal cell contains a considerable quantity of particles each
of which is capable of forming an entire organism similar to the
parents; these he calls "ides." According to _Weismann_, each ide is
subdivided into "determinants" from which each part of the body is
derived, being potentially predetermined in them. According to the
action of a yet unknown irritation male or female determinants develop
in each individual of the animal species with separate sexes. But if
the determinants are disordered, either by abnormal variations or by
pathological causes, hermaphrodites or monstrosities may be produced.
In animals which are normally hermaphrodite (snails, etc.), there is
only one kind of sexual determinant, while in polymorphous animals
(ants, etc.)