Thus, according to our view, the germ-plasm consists of ids, each of which contains all the determinants of the whole ontogeny, but usually in individually different quality. Returning for a moment to the processes by which the reduction of the chromosomes, that is, of the nuclear rods of germ-plasm in the ovum and sperm-cell is brought about, we recall the fact that this happens at the last two divisions of the germ-cell, the so-called 'maturing divisions.' In these the nuclear substance, as we have seen, is divided between the two daughter-nuclei in a manner quite different from the usual one, for a longitudinal splitting of the rods, bands, or spheres in the equatorial plane of the nucleus does not take place, but half the number of rods move into the right and half into the left daughter-nucleus without previous division, so that in each daughter-nucleus the number of rods is reduced to half (Fig. 76). [Illustration: FIG. 76. Diagram of the maturation divisions of the ovum. _A_, primitive germ-cell. _B_, mother-egg-cell, which has grown and has doubled the number of its chromosomes. _C_, first maturation division. _D_, immediately thereafter; _Rk_ 1, the first directive cell or polar body. _E_, the second maturation spindle has been formed; the first polar body has divided into two (2 and 3); the four chromosomes remaining in the ovum lie in the second directive spindle. _F_, immediately after the second maturation division; 1, the mature ovum; 2, 3, and 4, the three polar cells, each of these four cells containing two chromosomes.] Although the distribution of the rods in this manner takes place twice in succession, the normal number is not, as we have already seen, reduced to a quarter, because, long before the occurrence of the first maturing division, a duplication of the rods by means of longitudinal division had taken place, and thus the first division differs from an ordinary division in that the splitting of the rods does not take place during the process of dividing but long beforehand. Only the second maturing division differs from all other nuclear divisions known to us, since it is not associated with any splitting of the rods at all, but conveys half of the existing rods into each daughter-nucleus. It is the time reducing division, through which the number of the rods is reduced to one half[4]. [4] Recent investigations have shown that the reduction of the chromosomes does not always take place exactly in accordance with the scheme here indicated, but that it differs from it in many cases. But as investigations on this point are as yet by no means complete, I need not go into the question further; the ultimate result is the same in any case.