ed characters, as a short and convenient
expression, but have since changed the term to "transformative heredity"
(as distinguished from conservative). This term is preferable,
as inherited regressive modifications (degeneration, retrograde
metamorphisis, 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 thoroughgoing defence of it in his important work "Heredity" (London,
1908.)), as the most striking advance in evolutionary science. On the
other hand, the theory has been rejected by Herbert Spencer, Sir W.
Turner, Gegenbaur, Kolliker, 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 t