and other kinds of living creatures, as proved
by Galton and Pearson and many others who have dealt with such characters
as human stature, human eye color, and an extensive series of the
peculiarities of lower animals and even of plants.

The researches dealing with the physical basis of inheritance and its
location in the organism have yielded the most striking and brilliant
results. Darwin himself realized that the doctrine of natural selection
was incomplete, as it accepted at its face value the inheritance of
congenital racial qualities without attempting to describe the way an egg
or any other germ bears them, and he endeavored to round out his doctrine
of selection by adding the theory of pangenesis. According to this, every
cell of every tissue and organ of the body produces minute particles
called gemmules, which partake of the characters of the cells that produce
them. The gemmules were supposed to be transported throughout the entire
body, and to congregate in the germ-cells, which in a sense would be
minute editions of the body which bears them, and would then be capable of
producing the same kind of a body. If true, this view would lead to the
acceptance of Lamarck's or even Buffon's doctrine, for changes induced in
any organ by other than congenital factors could be impressed upon the
germ-cell, and would then be transported together with the original
specific characters to future generations. Darwin was indeed a good
Lamarckian.

But the researches of post-Darwinians, and especially those of the
students of cellular phenomena, have demonstrated that such a view has no
real basis in fact. Many naturalists, like Naegeli and Wiesner, were
convinced that there was a specific substance concerned with hereditary
qualities as in a larger way protoplasm is the physical basis of life. It
remained for Weismann to identify this theoretical substance with a
specific part of the cell, namely, the deeply staining substance, or
chromatin, contained in the nucleus of every cell. Bringing together the
accumulating observations of the numerous cytologists of his time, and
utilizing them for the development of his somewhat speculative theories,
Weismann published in 1882 a volume called "The Germ Plasm," which is an
immortal foundation for all later work on inheritance. The essential
principles of the germ-plasm theory are somewhat as follows. The chromatin
of the nucleus contains the determinants of hereditary qualities. In