of fertilization must be the basis of inheritance from the father. It
is equally true, as we shall see in the next chapter, that the
nucleus of the ovum and the nucleus alone transmits maternal
qualities. The material which conveys inheritable characters can be
seen and has been identified in both germinal cells; from each of
them the fertilized ovum derives equal amounts. As the parental
nuclei unite, the material which they contain intermingles and
establishes a new being; to attain full development, it requires
nothing further from the father, and nothing save nourishment from
the mother.

THE FIRST STEPS IN DEVELOPMENT.--Although the identity of the
spermatozoon is lost at the moment of fertilization, its influence
just then begins to be asserted. In the fertilized ovum the dawn of
development is shown at first by unusual activity within and later by
alterations upon the surface. Before very long the circumference of
the cell becomes indented as if a knife had been drawn around it, and
shortly two cells appear in place of one. These two cells in turn
divide, yielding four cells which grow and divide into eight. In this
manner division follows division until a multitude of cells have
sprung into existence, all of which cling together in the shape of a
ball. Development always proceeds in the same orderly way; evidently
it is governed by fixed laws which decree that the mass shall remain
for a while in the form of a ball, though the ball, at first solid,
soon becomes hollow.

While these changes are taking place the growing ovum is carried down
the oviduct a distance of four to six inches and finally comes to
rest in the uterus, where it is to dwell during the months necessary
to its complete development. The time consumed by this journey cannot