Telophase. Telophase is the closing period of mitosis and completes the organization of the daughter nuclei (see Fig. 7).
The chromosomes come to lie in a vacuole (Fig. 7 c, d, e) con taining nuclear sap and later the chromatin becomes distributed over a linin network and one or more nucleoli develop (Fig. 7 f> <") As was stated in Section I, the nuclear membrane probably represents the reaction of the granular kinoplasm to a fluid secretion around the chromosomes which becomes the nuclear sap (La wson, :O3a). However, the nuclear membrane is generally a definitely organized film, much more sharply defined than vacuolar membranes. The development of the linin network is not well understood. It is readily seen that the chromosomes become joined end to end and sometimes elon gate. The amount of chromatin diminishes as the linin substance appears, but it is not certain whether the chromatin is changed directly into linin, or whether the latter substance is a secretion: The best evidence rather favors the former view. Nucleoli are also believed to hold a very close chemical relation to chromatin.
It is uncertain whether or not the chromosomes lose their organic identity in the daughter nuclei. Investigations on this problem are surrounded by many difficulties. It has been claimed by Guignard ('99) for Naias and Strasburger (: oo) for several forms that the chromosomes may be followed with cer tainty through the period between the first and second mitosis in the spore mother cell. But other investigators have not been able to trace the chromosomes after telophase and are inclined to believe that the chromosome completely loses its identity in the resting nucleus. One of the last investigations of Lilium (Mottier, : 03) argues strongly for the latter view, and all who have followed nuclei from one mitosis into another know that the resting nucleus with its linin network and the granular chromatin present conditions that generally make the recognition of chromosomes impossible with the instruments and technique at our command, but this does not prove that they may not be present.
The theory of the permanence of the chromosome has met with much favor because it is argued that otherwise how could the number be maintained so regularly through immense numbers of mitoses. But it can hardly be said that the doctrine is established. It has also found favor because all the events of mitosis emphasize the importance of the chromosomes which are really the only enduring structures in the nucleus and have led to their being considered as the probable bearers of hereditary qualities.
FIG. 7. Telophase of Mitosis, spore mother-cell of Passiflora coerulea. A, very lateanaphase ; the daughter chromosomes are collected at the poles of the spindle, b, the commence ment of telophase ; the chromosomes have fused together and the daughter nucleus is represented by an irregularly shaped mass of chromatin. C, the presence of small lacunae within the mass of chromatin indicates the accumulation of nuclear sap in vacuoles. D, an increased amount of nuclear sap, still held however within the mass of chromatin, and consequent enlargement of the vacuole destined to become the nuclear cavity, e, the chromatin has begun to break up into small masses so that it no longer holds the nuclear sap which has established contact with the cytoplasm and is forming the nuclear plasma membrane, f, nuclear sap in contact on all sides with the cytoplasm and a complete nuclear membrane clearly established; chromatin is very much broken up and two nucleoli (n) have been formed, g, the resting nucleus with chromatin distributed in small masses connected by a network of linin threads; a nucleolus (n) is shown ; the zone outside the nuclear membrane is kinoplasm and its appearance indicates the approach of the second mitosis in the pollen mother-cell. All figures after Lawson.
