n Weismann's theory
are entirely coherent, and have been thought out to their conclusions with
praiseworthy determination.(67) To the theory as a whole, because of its
fundamental conception of preformation, and to its subsidiary hypotheses,
piece by piece, there has been energetic opposition on the part of the
upholders of the modern mechanical theory of epigenesis. This opposition
is most concretely and comprehensively expressed in Haacke's "Gestaltung
und Vererbung." The infinitely complex intricacy of Weismann's minute
microcosm within the germ-cell, indeed within every id in it, is justly
described as a mere duplication, a repetition in the infinitely little of
the essential difficulties to be explained. The complicated processes of
developing in the growing and inheriting organism cannot be explained,
they say, in terms of processes of the equally complex and likewise
developing germ-plasm. The complex, if it is to be explained at all, must
be explained by the simple--in this case by the functions of a homogeneous
uniform plasm.

At an earlier date Haeckel had made an attempt in this direction in his
theory of the "perigenesis of the plastidules." Peculiar states of
oscillation and rhythm in the molecules of the germ-substance, handed on
to it from the parent organism and transferable to all the assimilated
matter of the offspring, represent, according to this theory, the
principle which impels development to follow a particular course
corresponding to the type of the parents. This was a _physical_ way of
interpreting the matter. Other investigators have given a _chemical_
expression to their theoretical schemes for explaining heredity.

Haacke declares both these to be unsatisfactory, and replaces them by
morphological formative principles. It is the _structure_ of the otherwise
homogeneous living matter that explains morphogenesis and inheritance.
Minute "gemmae," homogeneous fundamental particles of living substance, not
to be compared to or confused with Darwin's "gemmules," are aggregated in
"Gemmaria," whose configuration, stability, symmetrical or asymmetrical
structure, and so on, are determined by the relative positions of the
gemmae to each other, and these in their turn control the organism and give
it a corresponding symmetrical or asymmetrical, a firmly or loosely
aggregated structure. The completed organism then forms a system in
organic equilibrium, which is constantly exposed to variations and
inf