In the Metaphases of the Karyokinesis begins the actual division of the cell. Each chromosome splits lengthwise into exactly similar halves, and these, in the Anaphases of the mitosis, drift out to the opposite poles of the spindle to form the daughter-nuclei of the new cells. The daughter-nuclei receive precisely equivalent portions of chromatin from the mother-nucleus, and this is an important fact in mitosis. As the chromosomes go toward the poles the cell-body begins to constrict at the equator. In the final phases, the Telophases, the cell divides in a plane passing through the equator of the spindle, and each daughter-cell receives half the chromosomes, half the spindle, and one of the asters with its centrosome. A daughter-nucleus is reconstructed in each cell from the chromosomes. The aster commonly disappears and the centrosome persists, usually outside the new nucleus, but sometimes within it. Every phase of mitosis is subject to variation in different kinds of cells, but the outline of the division given here is the fundamental method. The germ-cells differ from the body-cells in general by containing half the number of chromosomes characteristic of a given animal or plant. If the body-cell has, say, twenty-four chromosomes, the spermatozoön of the animal or plant from which the cells are taken will have twelve chromosomes and the ovum will have twelve. When the nuclei of these two cells unite in fertilization the resulting primordial cell will have the twenty-four chromosomes restored, the specific number for this plant or animal. In oögenesis and spermatogenesis the phases of "Reduction," wherein the ovum and spermatozoön get rid of half the chromosomes during the stages of maturation of these germ-cells, are somewhat similar for both sexes. The process is very complicated, but it is of importance in the theories of inheritance. All the physical characteristics in a human being that come to him from his parents and remoter ancestors are supposed, by the biologists, to reach him through the chromosomes in the nuclei of the single parental germ-cells. The maternal physical heredity is handed on through the chromosomes in the ovum. The fetus in the womb is a parasite, autocentric, feeding at the start from the deutoplasm, or yolk, in the ovum, and later from the supplies brought to it by the maternal blood. The physical material it gets directly from the mother is very probably all in the chromosomes of the fecundated ovum. Some weeks elapse, and the embryo is quite advanced before it begins to draw food from the mother at all. So far as the father is concerned, there is no doubt whatever that every physical and pathological characteristic that can be handed down--and there are many such qualities--must come through the chromosomes of the paternal spermatozoön. Certain physical characteristics are passed on for centuries in a family--the Norseman's body in northeastern Ireland, the skin-pigment in the American negro, and so