“Hertwig,” he continues, “puts his theory of conception thus:
‘Conception consists in the copulation of two cell-nuclei, which comes from a male and a female cell.…’
“As the phenomenon of heredity is inseparably connected with the reproductive process we may further conclude that these two copulating nuclei convey the characteristics which are transmitted from parents to offspring.” (Ev. of Man, p. 56.)
“As, moreover, there is a complete coälescence (fusion) 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 protoplastic bodies of the copulating cells also fuse together in the act of impregnation; the cell-body of the invading spermatozoön (the trunk and tail of the ciliated cell) is dissolved in the yelk of the female ovum. This coälescence is not so important as that of the [two] nuclei, but it must not be overlooked; and though the 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.” (Haeckel, Ev. Man, p. 56.)
In another place (p. 57) he says:
“It has been shown that the tiny sperm-cell (spermatozoön) is not subordinated to but co-ordinated with, the large ovum. The nuclei of the two cells, as the vehicle of the hereditary features of the parents, are of equal physiological importance. In some cases we have succeeded in proving that the mass of the active nuclear substance, which combines in the copulation of the two sexual nuclei is originally the same for both.
“These morphological facts are in perfect harmony with the familiar physiological truth that the child inherits from both parents; and that on the average they are equally distributed. I say ‘on the average’ because it is well known that a child may have a greater likeness to the father, or to the mother; that goes without saying, as far as the primary sexual characters (the sexual glands) are concerned. But it is also possible that the determination of the latter—the weighty determination whether the child is to be a boy or a girl—depends on a slight qualitative or quantitative difference in nuclein or the colored nuclear matter which comes from both parents in the act of conception.” (Ev. Man, p. 57.)
Haeckel continues, (p. 57):