s the bearers of heredity because they contain
samples, so to speak, of all the organs of the body.

In heredity, according to Weismann's theory, the egg is the centre
of control, the continuous germ-plasm the source of all transmitted
changes; according to Darwin's theory, the body is the source, and
the egg is derived in great part at least from it. If you put to the
two the time-honored question, Which is first, the owl or the egg?
Weismann would announce, with emphasis, The egg; Darwin would say,
The owl. One proposition is the converse of the other, and most
facts accord almost equally well with both theories.

In any family, devoted for generations to literary or artistic
pursuits, the children show, as a rule, an aptitude for such
pursuits not manifested by those of other families. According to the
Neo-Lamarckian view, this inherited aptitude is to a certain extent
the result of the constant exercise of these faculties through a
series of generations. The active efforts and voluntary disposition
of the parents have given an increased predisposition to the child.
"Quite the reverse," says Weismann, "the increase of an organ in the
course of generations does not depend upon the summation of
exercise taken during single lives, but upon the summation of more
favorable predispositions in the germ." "An organism cannot acquire
anything unless it already possesses the predisposition to acquire
it."[A]

[Footnote A: Weismann, Essays, pp. 85 and 171.]

We may accept or deny this last statement, but it is evident
that facts like these, and indeed the origin of most or all
characteristics involving use or disuse, may be explained almost
equally well by either theory.

But as far as the transmission of effects of somatic changes is
concerned, if protozoa undergo special modifications under the
influence of external conditions, will not the germ-cells undergo
special modification under the influence of changes in the
somatoplasm which forms their immediate environment? We must never
forget the close relationship between all the cells of the body, and
how slight a change in the body or its surroundings may conduce to
sterility or fertility. Such isolation and independence in the body,
on the part of the germ-cells, is opposed to all that we know of the
organic unity of the body, whose cells have arisen by the
differentiation of, and division of labor between, cells primitively
alike. The facts of bud-variation, of cha