528 P. W. WHITING 



the big chromosomes in the lower right hand corner. Nothing 

 of the sort can be made out in the cell shown in figure 10. In 

 figure 11 is drawn a diffuse body resembling the nucleolus. Figure 

 12 also shows a diffuse body as well as a diffuse element attached 

 to the outer member of one of the large pairs of chromosomes. 

 In figure 13 are two diffuse bodies, and in 14 a diffuse end of the 

 inner member of a large pair. This end is much more con- 

 densed than that shown in figure 12. In stage B of the meta- 

 phase and in anaphase these diffuse bodies and extra elements 

 are not seen. 



Figure 15 is a condition frequently observed, in which the 

 chromosomes are passing from stage A to stage B. The mem- 

 bers of the small pair are still considerably bent, those of one of 

 the larger pairs appear to be perfectly straight. The radial 

 symmetry of stage A is here lost and the six chromosomes are 

 beginning to assume the parallel arrangement of stage B. 



Figure 16 shows a metaphase in which the chromosomes have 

 assumed an approximately parallel arrangement. In the de- 

 scription of this stage and the stages immediately following, it 

 will be necessary to distinguish three axes — the polar axis and 

 two equatorial axes. The polar axis connects the poles of the 

 spindle and passes through the centre of the metaphase plate 

 and at right angles to it. An equatorial axis cutting the chromo- 

 somes transversely may be called the transverse axis, while an 

 equatorial axis lying parallel with the chromosomes and passing 

 between the members of the middle pair may be called the 

 parallel axis. In figures 16 to 28 the directions of the three 

 axes are represented by lines, each with a number at one end, 

 which indicates how many degrees of a circumference the end 

 of the line should be raised above the plane of the paper to get 

 the inclination of the axis. The polar axis is represented by a 

 solid line, the transverse axis by a dotted line, and the parallel 

 axis by a dot-and-dash line. Thus figure 16 is a polar view, 

 with the transverse and the parallel axes in the plane of the 

 paper. The three axes are of course always at right angles to 

 each other. If we disregard differences of size and irregular 

 bending of the chromosomes, we see that in stage B the meta- 



