537 
undivided into one or the other of the daughter nuclei. It is rather usual 
to find such a chromatin mass at or near each end of the spindle, but in 
numerous nuclei no such arrangement is observed. Occasionally one sees 
a dividing nucleus in which a mass of chromatin lies at the equator of the 
spindle, and sometimes this chromatin mass fails to divide or promptly 
to pass intact into either daughter nucleus. In fig. 20 is shown one 
such chromatin mass which appears as if it might fail to be included in 
either daughter nucleus. No care is taken in the multinucleate Opalinas 
5 
Figs. 12 and 13. Nuclei of O. antilliensis, in anaphase stages of mitosis. Both massive 
and granular chromosomes are shown. The preparation from which Fig. 13 was taken 
was injured before all the granular chromosomes were drawn. At the equator of 
Fig. 13 the spherical nucleolus is seen partially obscured by a massive daughter chro- 
mosome. In this species, as in other binucleate Opalinas, the nucleolus does not 
disappear or divide during mitosis, but passes bodily to one daughter nucleus. Both 
figures X 1780 diameters. 
to secure anything approaching an equasion division of the chromatin 
masses. 
Comparison of the resting nuclei in multinucleate Opalinas shows 
the apparent homology between the chromatin masses in the two groups, 
while study of the mitotic phenomena in the two groups indicates the 
similarity of the granular chromosomes in the two. The multinucleate 
and the binucleate forms take equal and very similar care of the granu- 
lar chromatin in mitosis, but they differ greatly in the attention paid to 
the massive chromatin in the division of the nuclei. The binucleate forms 
manipulate the chromatin masses as carefully as the granular chromo- 
