BoT.— Vol. II.] B YXBEE—LA VA TERA . 6*J 



from the wall a little, or had been used up at its inner edge 

 (figs. 7 and 8). These fibers, as has already been stated, 

 are probably derived from the elongated meshes of the 

 cytoplasm. The)?^ are of much greater diameter than the 

 linin threads, are smooth and stain deep blue. The extent 

 to which these fibers are visible varies greatly in different 

 cells. 



At some point the nuclear wall disappears and through 

 the gap thus formed the fibers immediately without the 

 nucleus begin to grow into the cavity (fig. 9). At first, 

 these fibers can be distinguished from the linin threads of 

 the nucleus by their greater diameter and smoother appear- 

 ance. As the nuclear wall continues to disappear, how- 

 ever, and the linin to thicken up, the fibers from within and 

 without the nucleus mingle in an interwoven mass in which 

 those of different origin cannot be distinguished (fig. 10). 



By the time the nuclear wall has entirely disappeared, 

 the nuclear cavity is filled with a mass of interwoven fibers 

 which is usually densest about the circle of chromosomes 

 which marks the situation of the old nuclear wall (fig. 10). 

 In some part of the nuclear space the fibers crowd closer 

 together to form a denser mass and at the same time tend 

 to range themselves so that they lie more or less parallel to 

 each other (figs. 11 and 12). Soon a number of projec- 

 tions appear in this mass as though it were being drawn out 

 at a number of points. Figure 13 shows an earlier and fig. 

 14 a later stage in this process. This continues until a dis- 

 tinct multipolar spindle is formed (fig. 15). 



Soon two principal groups of fibrous cones can be distin- 

 guished in the multipolar spindle and in each of these 

 groups one cone becomes the most prominent. Into these 

 two all others are soon absorbed by the continued straight- 

 ening out and converging of the fibers. Figure 16 shows a 

 spindle in which the cones have almost reached their final 

 position and in which there is only a trace of the third cone. 

 The completion of this process brings the chromosomes 

 into position at the equatorial plate just at the time that the 

 perfect bipolar spindle is formed. 



