240 BOTANICAL GAZETTE [APRIL 
rate, that the intranuclear centers are strongly anchored to that near- 
est portion of the nuclear membrane situated poleward from them. 
We may summarize these results pertaining to the nuclear division 
of Empusa sciarae and E. aphidis as follows. During the early 
stages of division the nuclei become less stainable and slowly change 
from a rounded to an oval shape. Two diverging centers of division, 
or centrosomes, become conspicuous near the middle of the nucleus. 
Fibers may now be seen radiating from the two intranuclear centers, 
some crossing the median line between the centers, others evidently 
anastomosing with fibers from the other system. The nucleus elon- 
gates still more and the opposed centers, each with its system of radi- 
ating fibers, diverge farther and farther apart. The centrosomes 
appear to increase in size as division proceeds, probably from the 
aggregation about them of the chromatic material in the radiating 
fibers. 
In cells which are comparatively short, a space filled with sap is 
early apparent between the diverging daughter masses, as well as in 
the interstices between the chromatic fibers. This sap increases in 
amount until in the oval, turgescent nuclei found in such short cells, 
the middle portion becomes filled with it, and we note a clearer central 
part, containing at first a few scattered fibers, separating the two polar, 
darkly-staining regions. On the final withdrawal of the last chro- 
matic filaments to the daughter-poles, the middle of the elongated 
nucleus becomes perfectly clear and transparent. The cytoplasm 
now encroaches on the median sap-cavity and, by constriction, cuts 
the mother-nucleus in two. In some instances, a double cytoplasmic 
constriction may take place, so that a vacuole filled with nuclear sap 
is cut off and left between the two daughter-nuclei. 
In long cells, on the other hand, or in filaments with few, far-sepa- 
rated septa, the nuclear sap does not accumulate in the manner just 
described; hence the nucleus, instead of becoming turgid with the 
liquid secretion, becomes early in the process of division constricted in 
the middle and greatly elongated, thus assuming the shape of an hour- 
glass. A few connecting strands in the constricted portions remain 
for some time, while the active polar regions, with their dense accumu- 
lation of chromatic material, become separated farther and farther, 
with the result that the two daughter-halves are finally pulled apart- 
