nges in the parent stock
due to grafting, and others, of which Mr. Darwin has given a summary
in the eleventh chapter of the first volume of his "Plants and
Animals under Domestication," have never been adequately explained
by Weismann in accordance with his theory. He has perhaps succeeded
in parrying their force by showing that some such explanation is
conceivable; they still point strongly against him.

Wilson has good reason for his "steadily growing conviction that
the cell is not a self-regulating mechanism in itself, that no cell
is isolated, and that Weismann's fundamental proposition is false."

But, granting the force of these criticisms, the question still
remains, Is the special effect of use or disuse transmissible? Would
the blacksmith's son have a stronger right arm?

1. The isolation and independence of the germ-cells, which Weismann
postulates as opposing this, can hardly be as great as he thinks. 2.
It is in his view impossible to conceive how these acquired
characteristics can in any way reach and affect the germ-cells in
such a manner as to reappear in the next generation. 3. All
variations can be explained by his own theory without such
transmission. Why then believe that acquired characteristics can in
some inconceivable way affect the germ-cells so as to reappear in
the next generation, as long as all the facts can be explained in a
more simple and easily conceivable manner?

As to his second argument, I would readily acknowledge that it is at
present difficult or impossible for me to conceive how any cell can
act upon another, except through the nutrient or other fluids which
it can produce. But though I cannot conceive how one cell can affect
another, I may be compelled to believe that it does so. And this
Weismann readily acknowledges.

Driesch changed by pressure the relative position of the cells of a
very young embryo, so that those which in a normal embryo would have
produced one organ were now compelled, if used at all, to form quite
a different one. And yet these displaced cells formed the organ
required of cells normally occupying this new position, not the one
for which they were normally intended. And the organ which they
would have builded in a normal embryo was now formed by other cells
transferred to their rightful place.

What made them thus change? Not change of substance or structure,
for the slight pressure could hardly have modified this. Not change
of nutriment. The on