ese "the organism produces germ-
cells afresh again and again, and that it produces them entirely from its
own substance." While by the second "the germ-cells are no longer looked
upon as the product of the parent's body, at least as far as their
essential part--the specific germ-plasm--is concerned; they are rather
considered as something which is to be placed in contrast with the _tout
ensemble_ of the cells which make up the parent's body, and the
germ-cells of succeeding generations stand in a similar relation to one
another as a series of generations of unicellular organisms arising by a
continued process of cell-division." {30}

On another page he writes:--

"I believe that heredity depends upon the fact that a small portion of
the effective substance of the germ, the germ-plasm, remains unchanged
during the development of the ovum into an organism, and that this part
of the germ-plasm serves as a foundation from which the germ-cells of the
new organism are produced. There is, therefore, continuity of the germ-
plasm from one generation to another. One might represent the germ-plasm
by the metaphor of a long creeping root-stock from which plants arise at
intervals, these latter representing the individuals of successive
generations." {31}

Mr. Wallace, who does not appear to have read Professor Weismann's essays
themselves, but whose remarks are, no doubt, ultimately derived from the
sequel to the passage just quoted from page 266 of Professor Weismann's
book, contends that the impossibility of the transmission of acquired
characters follows as a logical result from Professor Weismann's theory,
inasmuch as the molecular structure of the germ-plasm that will go to
form any succeeding generation is already predetermined within the still
unformed embryo of its predecessor; "and Weismann," continues Mr.
Wallace, "holds that there are no facts which really prove that acquired
characters can be inherited, although their inheritance has, by most
writers, been considered so probable as hardly to stand in need of direct
proof." {32}

Professor Weismann, in passages too numerous to quote, shows that he
recognises this necessity, and acknowledges that the non-transmission of
acquired characters "forms the foundation of the views" set forth in his
book, p. 291.

Professor Ray Lankester does not commit himself absolutely to this view,
but lends it support by saying (_Nature_, December 12, 1889): "It is
hardly necessar