“Quite in harmony with this new conception of the equivalence of the two gonads (ovum and spermatozoön) on the equal physiological importance of the male and female sex-cells and their equal share in the process of heredity, is the important fact established by Hertwig that in normal impregnation only one single spermatozoön copulates with one ovum; the membrane which is raised on the surface of the yelk immediately after one sperm-cell has penetrated, prevents any others from entering. All the rivals of the fortunate penetrator die without.” (Ev. Man, pp. 57-58.)
Sec. 17. Germ-Cell Does Not Contain Any Skeleton, Model nor Performed Outline of the Coming Embryo
At this point it should be noted that the stem-cell does not contain any skeleton, model nor other preformed outline of the coming embryo for the following reasons: (1) neither the ovum nor the spermatozoön contains any such skeleton, model nor outline; and if each of them contain such a thing, both would be destroyed when these primary cells fuse and merge into the germ-cell. (2) The germ-cell first divides into two, four, eight, sixteen, thirty-two, and sixty-four daughter-cells, and so on into the millions; and this segmentation of the stem-cell and daughter-cells would surely annihilate any skeleton, model or other outline that might exist in the germ-cell; (3) the germ-cell first divides into two daughter-cells and so on, to infinity, as already stated; and these daughter-cells form what are called “germ-layers” or sheets of cells from which the human body and all of its organs and parts are built up. (Haeckel, Ev. Man, pp. 14, 16, 59, 92; Encyc. Brit., (9th ed.) 3, p. 682; 8, pp. 165, 744; 24, p. 631; Cent. Dic. 3, p. 2500, “Germ-layer.”)
This mode of growth, by the segmentation of cells and formation of germ-layers, is called “epigenesis” which Huxley defines as “the successive differentiation of a relatively homogeneous rudiment, into the parts and structures, which characterize the adult.” (Encyc. Brit. 8, p. 744. Cent. Dic. 3, p. 1968, “Epigenesis.”)
According to the theory of epigenesis, which is now held by all the scientific world, the human body grows anew from the germ-cell, without any skeleton model or any other kind of preformation.
“Every living thing,” says Huxley, “is evolved from a particle of matter, in which no trace of the distinctive characters of the adult form of that living thing is discernible. This particle is termed a germ.” (Encyc. Brit. (9 ed.) 8, p. 746.)
He defines a germ as “matter potentially alive, and having, within itself, the tendency to assume a definite living form;” and says that this definition “appears to meet all the requirements of modern science.” (Encyc. Brit. (9 ed.) 8, p. 746.)
“In all cases,” he says, “the process of evolution [growth] consists in a succession of changes of the form, structure and functions of the germ [fertilized ovum], by which it passes, step by step, from an extreme simplicity, or relative homogeneity, of visible structure to a greater or less degree of complexity or heterogeneity; and the course of progressive differentiation is usually accompanied by growth, which is effected by intussusception.” (Encyc. Brit. 8, p. 746.)
Huxley is surely mistaken in saying that “the process of evolution [development and growth] consists in a succession of changes in the form, structure and functions of the germ,” for the germ (fertilized ovum) immediately divides into two daughter-cells, these into four, these into eight, sixteen and so on to infinity. Thus, it appears that germ (germ-cell) becomes “a drop in the sea,” its identity being wholly lost. Huxley states this fact, in substance, in the quotation below.