sequence of sexual generation.]

[Footnote 215: Darwin's _Animals and Plants_, vol. ii. pp. 23, 24.]

[Footnote 216: In his essay on "Heredity," Dr. Weismann discusses many
other cases of supposed inheritance of acquired characters, and shows
that they can all be explained in other ways. Shortsightedness among
civilised nations, for example, is due partly to the absence of
selection and consequent regression towards a mean, and partly to its
individual production by constant reading.]

[Footnote 217: Weismann explains instinct on similar lines, and gives
many interesting illustrations (see _Essays on Heredity_). He holds
"that all instinct is entirely due to the operation of natural
selection, and has its foundation, not upon inherited experiences, but
upon variations of the germ." Many interesting and difficult cases of
instinct are discussed by Darwin in Chapter VIII of the _Origin of
Species_, which should be read in connection with the above remarks.

Since this chapter was written my attention has been directed to Mr.
Francis Galton's _Theory of Heredity_ (already referred to at p. 417)
which was published thirteen years ago as an alternative for Darwin's
theory of pangenesis.

Mr. Galton's theory, although it attracted little attention, appears to
me to be substantially the same as that of Professor Weismann. Galton's
"stirp" is Weismann's "germ-plasm." Galton supposes the sexual elements
in the offspring to be directly formed from the residue of the _stirp_
not used up in the development of the body of the parent--Weismann's
"continuity of the germ-plasm." Galton also draws many of the same
conclusions from his theory. He maintains that characters acquired by
the individual as the result of external influences cannot be inherited,
unless such influences act directly on the reproductive
elements--instancing the possible heredity of alcoholism, because the
alcohol permeates the tissues and may reach the sexual elements. He
discusses the supposed heredity of effects produced by use or disuse,
and explains them much in the same manner as does Weismann. Galton is an
anthropologist, and applies the theory, mainly, to explain the
peculiarities of hereditary transmission in man, many of which
peculiarities he discusses and elucidates. Weismann is a biologist, and
is mostly concerned with the application of the theory to explain
variation and instinct, and to the further development of the theory of
evolution. He has