oduction by another tissue of some specific poison which causes the
nervous system to react in a definite way. We have mentioned these
possibilities merely to indicate how complex the problem may turn out to
be. Though there is no doubt that mental ability is inherited, what it is
that is transmitted, whether factors involving the quality and structure of
the nervous system itself, or factors involving the production of specific
poisons by other tissues, or both together, is at present uncertain.

Little as is known to-day of heredity in man, that little is of
extraordinary significance. The qualities of men and women, physical and
mental, depend primarily upon the inherent properties of the gametes which
went to their making. Within limits these qualities are elastic, and can be
modified to a greater or lesser extent by influences brought to bear upon
the growing zygote, provided always that the necessary basis is present
upon which these influences can work. If the mathematical faculty has been
carried in by the gamete, the education of the zygote will enable him to
make the most of it. But if the basis is not there, no amount of education
can transform that zygote into a mathematician. This is a matter of common
experience. Neither is there any reason for supposing that the superior
education of a {182} mathematical zygote will thereby increase the
mathematical propensities of the gametes which live within him. For the
gamete recks little of quaternions. It is true that there is progress of a
kind in the world, and that this progress is largely due to improvements in
education and hygiene. The people of to-day are better fitted to cope with
their material surroundings than were the people of even a few thousand
years ago. And as time goes on they are able more and more to control the
workings of the world around them. But there is no reason for supposing
that this is because the effects of education are inherited. Man stores
knowledge as a bee stores honey or a squirrel stores nuts. With man,
however, the hoard is of a more lasting nature. Each generation in using it
sifts, adds, and rejects, and passes it on to the next a little better and
a little fuller. When we speak of progress we generally mean that the hoard
has been improved, and is of more service to man in his attempts to control
his surroundings. Sometimes this hoarded knowledge is spoken of as the
inheritance which a generation receives from those who have g