384 
Freda M. Baehmann 
fully formed the nuclear membrane is 110 longer so clearly defined as 
in the resting nuclei, and very soon it eorapletely disappears (Figs. 10 — 12). 
The entire membrane does not disappear at onee, the dissolution being 
more rapid in some parts. In some eases (Fig. 11), tliere is plainly a een- 
trosome-like body at each end of the spindle. This body is more easily 
seen when the spindle lies parallel to the plane in which the seetion was 
ent, because if the spindle is diagonal to the surfaee of the seetion it is 
often difficult to distinguish a body at the poles from the ehromosomes. 
In the division figure shown in Fig. 11, there appear fo be two granules 
at the pole “a”; there are also two stained bodies at the opposite pole, 
but it is possible that the larger one of these bodies, because of its greater 
size and its position somewhat at one side of the axis of the spindle, is 
the remnant of the nueleole. At the equatorial plate stage there seem 
to be fixe or six ehromosomes. The daughter nuclei may enlarge con- 
siderably (Fig. 3) before they move apart. The chromatin, as seen in 
Figure 3 at a, may remain massed until both the cell and the daughter 
nucleus have inereased considerably in size, or, as seen in the same figure, 
may very soon beeome distributed as in the resting niüeeus. After some 
time, judging from the number of binueleate cells which may be found, 
the nuclei migrate one toward either end of the cell and only then is the 
partition formed which separates the daughter cells. 
I have not determined exactly how this partition is formed. It is 
possible that it is formed by a furrowing in of the plasma membrane 
from each side of the cell, as has been deseribed for CJadophora and other 
algae. The partition never becomes heavy, and I am inclined to think 
that there is no deposition of wall material in the cleft. When first formed 
the partition appears to be continuous (Fig. 2); liowever, very frequently 
threads of cytoplasm in adjacent cells meet at the same point in the 
septum and one cannot be certain that there is no protoplasmic Connec- 
tion. While the partition is not heavy, its position between cells is made 
very conspicuous by the appearance of material which is most frequently 
granulär and which is deposited all around the edge of the partition but 
outside of the lateral wall (Figs. 2, 3, 5, 8). These figures show an out- 
side view of the cross walls. Seen in optical seetion (Fig. 10), it is very 
evident that this granulär material is entirely outside the cell. Such 
granules are never found on newly formed partitions but only on those 
between old and quite large cells. Oceasionally this material is not depos- 
ited in the form of granules but appears to form a homogeneous thicken- 
ing around the wall (Figs. 4, 6, 7). In one case (Fig. 9, at a ), I have found 
material deposited around the lateral cell wall at a place other than where 
