arwin's contribution to the problem of the sixth order was his rather
vague theory of "Pangenesis." The living organism, according to him, forms
in its various organs, parts, and cells exceedingly minute particles of
living matter (gemmules), which, "in some way or other," bear within them
the special characteristics of the part in which they are produced. These
may wander through the organism and meet in the germ-plasm, and then, when
a child-organism is produced, they "swarm," so to speak, in it again "in
some way or other," and in some fashion control the development. This
gemmule-theory was too obviously a _quid pro quo_ to hold its ground for
long. Various theories were elaborated, and the world of the invisibly
minute was flooded with speculations.

The most subtle of these, on the side of consistent Darwinism, is that of
Weismann, a pronounced preformation theory which has been increasingly
refined and elaborated in the course of years of reflection. According to
Weismann, the individual parts and characteristics of the organism are
represented in the germ-plasm, not in finished form, but as "determinants"
in a definite system which is itself the directing principle in the
building up of the bodily system, and with definite characteristics, which
determine the peculiarities of the individual organs and parts, down to
scales, hairs, skin-spots, and birth-marks. As the germ-cells have the
power of growth, and can increase endlessly by dividing and re-dividing,
and as each process of division takes place in such a way that each half
(each product of division) maintains the previous system, there arise
innumerable germ-cells corresponding to one another, from which,
therefore, corresponding bodies must arise (inheritance). It is not in
reality the newly developed bodies which give rise to new germ-cells and
transfer to them something of their own characters; the germ-cells of the
child-organism develop from that of the parent ("immortality" of the
germ-cells). Therefore there can be no inheritance of acquired characters,
and no modifications of type through external causes; and all variations
which appear in a series of generations are due solely to internal
variations in the germ-cells, whether brought about by the complication of
their system through the fusion of the male and female germ-cells, or
through differences in the growth of the individual determinants
themselves. The numerous subsidiary theses interwoven i