As, moreover, there is a complete coalescence of the mutually
attracted nuclear substances in conception, and the new nucleus formed
(the stem-nucleus) is the real starting-point for the development of
the fresh organism, the further conclusion may be drawn that the male
nucleus conveys to the child the qualities of the father, and the
female nucleus the features of the mother. We must not forget,
however, that the protoplasmic bodies of the copulating cells also
fuse together in the act of impregnation; the cell-body of the
invading spermatozoon (the trunk and tail of the male ciliated cell)
is dissolved in the yelk of the female ovum. This coalescence is not
so important as that of the nuclei, but it must not be overlooked;
and, though this process is not so well known to us, we see clearly at
least the formation of the star-like figure (the radial arrangement of
the particles in the plasma) in it (Figures 1.26 to 1.27).

The older theories of impregnation generally went astray in regarding
the large ovum as the sole base of the new organism, and only ascribed
to the spermatozoon the work of stimulating and originating its
development. The stimulus which it gave to the ovum was sometimes
thought to be purely chemical, at other times rather physical (on the
principle of transferred movement), or again a mystic and
transcendental process. This error was partly due to the imperfect
knowledge at that time of the facts of impregnation, and partly to the
striking difference in the sizes of the two sexual cells. Most of the
earlier observers thought that the spermatozoon did not penetrate into
the ovum. And even when this had been demonstrated, the spermatozoon
was believed to disappear in the ovum without leaving a trace.
However, the splendid research made in the last three decades with the
finer technical methods of our time has completely exposed the error
of this. It has been shown that the tiny sperm-cell is NOT