etc.) come under the same head.

Transformative heredity--or the transmission of acquired
characters--is one of the most important principles in evolutionary
science. Unless we admit it most of the facts of comparative anatomy
and physiology are inexplicable. That was the conviction of Darwin no
less than of Lamarck, of Spencer as well as Virchow, of Huxley as well
as Gegenbaur, indeed of the great majority of speculative biologists.
This fundamental principle was for the first time called in question
and assailed in 1885 by August Weismann of Freiburg, the eminent
zoologist to whom the theory of evolution owes a great deal of
valuable support, and who has attained distinction by his extension of
the theory of selection. In explanation of the phenomena of heredity
he introduced a new theory, the "theory of the continuity of the
germ-plasm." According to him the living substance in all organisms
consists of two quite distinct kinds of plasm, somatic and germinal.
The permanent germ-plasm, or the active substance of the two
germ-cells (egg-cell and sperm-cell), passes unchanged through a
series of generations, and is not affected by environmental
influences. The environment modifies only the soma-plasm, the organs
and tissues of the body. The modifications that these parts undergo
through the influence of the environment or their own activity (use
and habit), do not affect the germ-plasm, and cannot therefore be
transmitted.

This theory of the continuity of the germ-plasm has been expounded by
Weismann during the last twenty-four years in a number of able
volumes, and is regarded by many biologists, such as Mr. Francis
Galton, Sir E. Ray Lankester, and Professor J. Arthur Thomson (who has
recently made a thorough-going defence of it in his important work
_Heredity_),[129] as the most striking advance in evolutionary
science. On the other hand, the theory has been rejected by Herbert
Spencer, Sir W. Turner, Gegenbaur, Koelliker, Hertwig, and many others.
For my part I have, with all respect for the distinguished Darwinian,
contested the theory from the first, because its whole foundation
seems to me erroneous, and its deductions do not seem to be in accord
with the main facts of comparative morphology and physiology.
Weismann's theory in its entirety is a finely conceived molecular
hypothesis, but it is devoid of empirical basis. The notion of the
absolute and permanent independence of the germ-plasm, as
distinguished