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, L.C., 1904 ; C, D, after Schneider, Fest.ffir 



R. Hertwig, 1910.) A, C, telophase ; B, D, prophase. 



or anaphase. This view is held by many workers, e.g. 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 (19 13), 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 stages. 



