. Cytology, with special reference to the metazoan nucleus. Cells. THE CHROMOSOMES 15 nucleus is formed by the intertwining of these threads, which at the same time become irregular and broken up (as regards the chromatin ; the linin basis of the threads remains continuous) and connected with each other by anastomoses. Prophase consists of the reverse process. There are two variations on this view : (a) Two threads are formed from each chromosome, and hence the prophase chromosomes are from the first double, and even the resting nucleus is duplex as regards its chromatin constituents. Accordin
. Cytology, with special reference to the metazoan nucleus. Cells. THE CHROMOSOMES 15 nucleus is formed by the intertwining of these threads, which at the same time become irregular and broken up (as regards the chromatin ; the linin basis of the threads remains continuous) and connected with each other by anastomoses. Prophase consists of the reverse process. There are two variations on this view : (a) Two threads are formed from each chromosome, and hence the prophase chromosomes are from the first double, and even the resting nucleus is duplex as regards its chromatin constituents. According to this view, therefore, the real division of the chromosomes into daughter chromosomes takes place not in prophase but in the previous telophase. Fig. 7. Larva of Salamandra maculosa. (A, B, after Kowalski, , 1904 ; C, D, after Schneider, R. Hertwig, 1910.) A, C, telophase; B, D, prophase. or anaphase. This view is held by many workers, Schneider (1910), Salamandra (Fig. 7) ; Dehorne (1911), Salamandra and (1911) Allium (Fig. 8), with, however, a different interpretation as to the part played by the anaphase division in the following mitosis; Lundegardh (1913), Allium', Schustow (1913), Allium. (b) Only one thread is normally produced from each chromosome in telophase, the di\dsion of the chromosomes taking place in prophase. [Bonnevie (1908), Ascaris (Fig. 6) and Allium (Fig. 8) ; Boveri (1909), Ascaris, exceptionally; Vejdovsky (1911), Ascaris.] It is clear that where different workers base such contradictory conclusions on identical material, the reason for their differences must be sought largely in the difticulty of interpreting these confused Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Agar, Wilfred Eade, 1882-. London, Macmillan
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