the transmission of particular definite mental
traits, such as the various aspects of memory, association, attention,
temperament, etc. Before we can speak with any certainty here, we must
make very careful experimental studies of these mental traits in parents
and offspring. No such work has been done. All we have at the present
time is the result of general observation.

=Improvement of the Race.= Eugenics is the science of improvement of the
human race by breeding. While we can train children and thereby make
them much better than they would be without such training, this training
does not improve the stock. The improvement of the stock can be
accomplished only through breeding from the best and preventing the poor
stock from leaving offspring. This is a well-known principle in the
breeding of domestic animals.

It is doubtless just as true in the case of human beings. The hygienic
and scientific rearing of children is good for the children and makes
their lives better, but probably does not affect their offspring. We
should not forget that all the social and educational influences die
with the generation that receives them. They must be impressed by
training on the next generation or that generation will receive no
influence from them. The characters which we acquire in our lifetime
seem not to be transmitted to our children, except through what is known
as social heredity, which is merely the taking on of characteristics
through imitation. Our children must go through all the labor of
learning to read, write, spell, add, multiply, subtract, and divide,
which we went through. Moral traits, manners and customs, and other
habits and ideals of social importance must be acquired by each
successive generation.

=Heredity _versus_ Environment.= The question is often asked whether
heredity or the influence of environment has the most to do with the
final outcome of one's life. It is a rather useless question to ask, for
what a human being or anything else in the world does depends upon what
it is itself and what the things and forces are that act upon it.
Heredity sets a limitation for us, fixes the possibilities. The
circumstances of life determine what we will do with our inherited
abilities and characteristics. Hereditary influences incline us to be
tall or short, fat or lean, light or dark. The characteristics of our
memory, association, imagination, our learning capacity, etc., are
determined by heredity. Of course