Opalina. 243 
ally, but by no means always, it is the anterior nucleus, in 0. 
intestinalis, which is in the more advanced condition of the two, if 
they be different, although in this nucleus the restoration of fully 
typical structure after mitosis is somewhat delayed because of the 
late appearance of the new nucleolus. One would naturally expect 
the chromatin of this nucleus to be in the less advanced condition 
of the two, if there is to be a difference. 
Chromatin spherules. 
In this description of mitosis no reference has been made to 
one of the most interesting series of phenomena, i. e. the diminution 
of the chromatin by the throwing off and dissolving of a large pro- 
portion of the material of the chromatin masses into which the 
chromatin ribbon constricts as described. 
Mention has been made of the granules present in the chromo- 
somes at all times. These are small, usually no larger than the 
achromatic granules of the nucleus. In addition to these, in O. im- 
testinalis, many larger spherical granules appear during the late 
spireme stage, or as soon as the chromatin ribbon is broken into 
separate masses (Figs. 71—73, Pl. XIX; 21, 22, 28—31, Pl. XV). 
These spherules1) are formed at the surface of the chromatin masses 
and protrude beyond their contour. They are of different sizes, 
not only in the same nucleus, but upon the same chromatin mass. 
They are compact and seem homogeneous with all stains used. 
Before the spindle for the next mitosis forms, the chromatin sphe- 
rules break away from the now divided chromatin ribbon and come 
to lie free in the nucleus (Fig. 72, Pl. XIX). At first they stain 
very strongly, but. by the time the spindle for the next mitosis is 
formed, they stain much more faintly (Fig. 75, Pl. XX, also Figs. 23, 
Pl. XV; 65, Pl. XIX; 79, Pl. XX). By the time the anaphase stage 
is reached they usually can no longer be recognised, though occas- 
ionally they can be faintly discerned even in the early telophases. ”) 
The formation of chromatin spherules was not seen in the 
gametes or zygotes or in the gamete mother-cells. I did not 
') In the preliminary notice of this paper I called these structures sometimes 
spherules and sometimes spheres. It seeme best to call them chromatin spherules 
and to reserve the term chromatin spheres for certain much larger bodies formed 
in and extruded from the nuclei in the spring before the sexual phenomena occur. 
*) Fig. 94, Pl. XXI, shows a pair of abnormal nuclei in the anterior of which 
are granular bodies which may be dissolving chromatin spherules. 
