HEREDITY.--The transmission of bodily resemblance and of traits of
character from parent to child is a broad and complicated subject,
whose fundamental principles biologists are just beginning to grasp.
The facts thus far established regarding heredity relate chiefly to
plants and to the lower animals. There is no doubt whatever that the
meager knowledge we possess of heredity in man will be amplified and
will ultimately indicate on the one hand the marriages which are
advisable and, on the other hand, those which are not. Indeed, the
foundations for a science called Eugenics, which purposes to improve
the human race in this way, have already been laid. It is barely a
decade, however, since our knowledge of heredity has approached that
order and system which entitle it to be ranked as a science; and in
this brief period great strides could hardly be expected in its most
intricate field, that of human inheritance.

The modern teachings of heredity are of interest to us, nevertheless,
since they intimate the time when a child's inheritance is fixed and
the means by which hereditary characters are conveyed. To understand
these fundamental points we must recall that at the moment of
conception a male germinal cell combines with a female cell, and that
this act, which is named fertilization, brings together vital
elements from the two parents. We have seen that the spermatozoon
represents the solitary contribution of the father toward the
development of the child, and the spermatozoon, therefore, must
convey the material basis of paternal inheritance. Similarly we might
expect the ovum to be the bearer of the maternal qualities inherited
by the child. This is actually true; but much of the evidence is of a
technical character and must be omitted. Yet an experiment
successfully conducted by Castle and Phillips will indicate, even to