In the indirect division the nucleus is divided by a complicated process. Simultaneously the cytoplasm and the membrane are also cleft in two parts. In the typical cell division two parallel series of changes occur nearly simultaneously, one affecting the nucleus, the other the cytoplasm. The chromatin which is usually (Fig. A, Cut XXVIII) in form of scattered granules, arranged along the linin network, becomes aggregated together in certain definite areas (Fig. B), forming usually a convoluted thread or skein. This skein appears either in form of a long filament or divided up into a series of segments called “chromosomes” (Fig. C). The number of chromosomes is constant for each species of plant and animal. Thus, in the common mouse these chromosomes are twenty-four in number, in the onion sixteen, in the sea-urchin eighteen, etc. The number is always an even one. By this time the nuclear membrane has disappeared, and the chromosomes appear usually as a collection of bands lying free in the cytoplasm (Fig. D). At the same time, another series of changes has gone through the centrosome and the cytoplasm in the cell-body. The centrosome assumes an ellipsoid form, constricts transversely into a dumb-bell-shaped figure (Fig. B), and divides into two daughter centrosomes. Around each of them is gradually developed a stellate figure composed of a countless number of delicate fibrils, radiating out in all directions from the centrosome as a centre. The entire constellation is called “aster.” The two asters grow in size progressively as the two centrosomes move apart toward the poles of the cell (Fig. C). Between the two asters a spindle-shaped system of delicate fibrils appears stretching from one aster to the other which is called “central-spindle” (Fig. D). The two asters together with the central-spindle represent the “Amphiaster”. [Illustration: CUT XXVIII. _Mitosis or indirect division of a cell._ cy, cytoplasm; n, nucleus; c, centrosome; nu, nucleolus; l, linin; sk, skein; a, aster; cs, central spindle; ch, chromosome; u, U-shaped loops; mf, mantle fibres; cf, connecting fibrils.] At this point the centrosomes or the asters and the chromosomes begin to work together. A system of fibrils grows out from each aster which attach themselves to the individual chromosomes. The latter bent into U-shaped loops arrange themselves in a circle around the centre of the spindle and form the “equatorial plate” (Fig. E). The chromosomes are now longitudinally split, and the halves move toward the poles as if drawn by the mantle fibres (Fig. F). The loops are still connected with each other by these connecting mantle fibres (Fig. G and H). The new U-shaped loops form now new skeins at each pole (Fig. I). The chromatin granules now separate along the thread of the linin network, and the new nuclear membranes are formed (Fig. K).