222 J. MCA. KATER. 



EXPLANATION OF PLATES. 



All figures drawn from sections 4 micra thick with aid of Abbe camera lucida 

 and Leitz 2 mm. oil immersion lens. Figs, i, 4, 7, 10, n, 13, and 15 to 22 from 

 material fixed in Flemming's strong; the remaining figures from sections fixed in 

 Bouin's. All sections stained with iron-alum-hjematoxylin and lightly counter- 

 stained with eosin. With the exception of figures 21 and 22 all drawings represent 

 structures in two dimensions. Magnification 1900 X. 



PLATE i. 



FIG. i. The chromosomes have become contiguous at the poles of the spindle. 

 Individual chromosomes can be traced by their rounded ends. 



FIG. 2. Vacuolization is beginning. Rounded ends still indicate limits of each 

 chromosome. 



FIG. 3. Vacuolization continued. Disperse chromatin granules in chromo- 

 somal vesicles. 



FIG. 4. Note non-vacuolized portion of each chromosome. Linin strands 

 represent line of contiguity of different chromosomes. Chromatin granules in 

 vesicles. 



FIG. 5. The linin borders of the chromosomes are still prominent and the non- 

 vacuolized ends of the chromosomes are joining. 



FIG. 6. A continuation of the changes illustrated by Fig. 5. Note lower nucleus 

 where the two last non-vacuolized portions of chromatin are joining to form 

 chromatin nucleolus or karyosome. Disperse chromatin granules are located 

 principally around the periphery of the nucleus. 



FIG. 7. Approximately the same stage of development as Fig. 6. The section 

 was so cut that the nucleolus does not appear in one of the daughter nuclei. Note 

 that the linin strands are not parallel in this one. 



FIG. 8. Completion of the joining of the non-vacuolized chromosome ends to 

 form the nucleoli. Nucleolus approximately spherical in one daughter nucleus. 

 Linin sheaths of chromosomes still prominent. 



FIG. 9. Polar view of reconstructing nucleus. This nucleus is at about the 

 same stage of development as Fig. 5. The linin strands are not parallel as in 

 side view. 



