y to say that it has never yet been shown experimentally
that _anything_ acquired by one generation is transmitted to the next
(putting aside diseases)."

Mr. Romanes, writing in _Nature_, March 18, 1890, and opposing certain
details of Professor Weismann's theory, so far supports it as to say that
"there is the gravest possible doubt lying against the supposition that
any really inherited decrease is due to the inherited effects of disuse."
The "gravest possible doubt" should mean that Mr. Romanes regards it as a
moral certainty that disuse has no transmitted effect in reducing an
organ, and it should follow that he holds use to have no transmitted
effect in its development. The sequel, however, makes me uncertain how
far Mr. Romanes intends this, and I would refer the reader to the article
which Mr. Romanes has just published on Weismann in the _Contemporary
Review_ for this current month.

The burden of Mr. Thiselton Dyer's controversy with the Duke of Argyll
(see _Nature_, January 16, 1890, _et seq._) was that there was no
evidence in support of the transmission of any acquired modification. The
orthodoxy of science, therefore, must be held as giving at any rate a
provisional support to Professor Weismann, but all of them, including
even Professor Weismann himself, shrink from committing themselves to the
opinion that the germ-cells of any organisms remain in all cases
unaffected by the events that occur to the other cells of the same
organism, and until they do this they have knocked the bottom out of
their case.

From among the passages in which Professor Weismann himself shows a
desire to hedge I may take the following from page 170 of his book:--

"I am also far from asserting that the germ-plasm which, as I hold, is
transmitted as the basis of heredity from one generation to another, is
absolutely unchangeable or totally uninfluenced by forces residing in the
organism within which it is transformed into germ-cells. I am also
compelled to admit it as conceivable that organisms may exert a modifying
influence upon their germ-cells, and even that such a process is to a
certain extent inevitable. The nutrition and growth of the individual
must exercise some influence upon its germ-cells . . . "

Professor Weismann does indeed go on to say that this influence must be
extremely slight, but we do not care how slight the changes produced may
be provided they exist and can be transmitted. On an earlier page (p.