512- THEOPHILUS S. PAINTER 



side of the centrosphere pushing the rays forward in these re- 

 gions and dragging the whole aster along wdth it. 



Figure 3 shows an egg in which the bending of the rays is still 

 more pronounced. The two areas of twisting are to be made out, 

 less clearly than in figure 2, and a careful inspection shows that 

 the rays in these two regions run forward and then backwards 

 as described for the other cases. This egg is particularly inter- 

 esting as it shows how the astral rays have been pulled free from 

 their anchorings in the cytoplasm. This egg shows, perhaps, the 

 condition most commonly found. 



In figure 4 we see an egg in which the twisting is very clearly 

 localized around two points. The section cuts the aster some- 

 what obliquely so that only one center shows distinctly. A 

 faint spindle may be seen in the centrosphere connecting the 

 two centers. Again we note that the course of the rays at the 

 two centers of movement is the same as in the other eggs. One 

 further point of interest lies in the position of the chromosomes. 

 It will be noted that in the region of bending two chromosomes 

 have been pulled away from their mates. 



Figure 5 shows an egg in which the two centers have moved 

 far apart. Faint traces of the centrosphere may still be seen con- 

 necting them. The chromosomes lie, for the most part, around 

 one center. (This is shown both in this section and in those ad- 

 joining it.) 



Figures 6 and 7 show later stages of the spiral asters. In fig- 

 ure 6 the chromosomes are scattered, though they lie in the 

 plane of the spindle connecting the two centers. In figure 7, 

 an equatorial plate has been formed. (In the latter case the 

 plane of section is a trifle obHque to that of the spindle.) 



In figure 8 we have an egg which appears to be the final stage 

 of the spiral aster. The rays are no longer bent, they appear 

 somewhat finer than those of the preceding figures. The only 

 trace of the bending is seen in the spindle itself. A division of 

 the chromosomes has taken place, though the latter fact is not 

 clear from the figure. 



The eggs shown in the figures, with the exception of 3, per- 

 haps, seem to form continuous steps in a process of shifting of the 



