at is
there has no resemblance to what it will be in time. The biologist
finds in the nucleus or central core of every growing and reproducing
cell certain minute bodies which Weissmann believes do much to
determine the growth of the rest of the cell. He believes also that
there are many more such "determinants" than are necessary for the
reproduction of the cell. Each of these determinants may be fitted to
produce slightly different results, but what decides which of them
shall have its own way is quite uncertain. It may be that one
determinant happens to be more favorably placed than others in the
cell and that it has consequently secured more of the nourishment that
comes to the cell in the blood of its parent. If this is true it would
certainly be favored in the competition. We are becoming quite certain
that whatever variations arise really start in the egg. The simplest
conception as to the cause of variation would seem to be varied
experience. One man trains his brain, another his hand; and in each
case the organ so trained develops. But science is strongly of the
mind that such influence does not reach the next generation.

A musician may have taught his fingers to be nimble; may have given
them speed of motion and precision in their action. No child of his
born after he acquired this wonderful facility of execution is any
more likely to be a skilled musician than a child born before he had
ever practiced enough to be anything more than a crude performer.
Science is nearly certain that his children are just as likely to be
talented along musical lines if he himself never had become a
musician, simply because he had it in him to be a musician. In other
words, they may inherit the talent which he developed, but they
inherited it not because he developed it, but because it was in him to
be developed. This is in accordance with the famous principle that
there is no inheritance of acquired characters. We shall touch this
question a little more fully in a later chapter, in speaking of the
development of the evolution theory since Darwin's time.

If we are right in this matter, and we certainly are nearly right,
variation must take place for the most part in the germ. These
variations may not show until the animal has grown up, but they must
have taken place among the determinants in the germ cell or they would
not reappear in subsequent generations.

There is another process by which new variations may arise and wh