140 The Significance of Sex, [ Feb. 
in a the phenomena are restricted to the nucleus; in 4 to the hyaline body which 
holds the nucleolus, and at last, in ç, the nucleolus is sending out ray-like pseudo- 
podia, which become the chromatin fibrils. A spindle is finally formed with a hy- 
aline mg at each end. d-A show different states of a nucleus in the “ resting” 
condition. In æ we have a nucleolus and paranucleolus ; these segment and become 
related, as ine and f. Ing the nucleolus is much segmented. 4 shows us the nu- 
cleus preparing for division ; the aa protoplasm sheet saa the nucleus is amee- 
boid, as is also the nucleolus. The former, at last, gathers as two polar caps (/), 
while the latter dissolves to granules (); ; at first the granules are in the centre of the 
nucleus, then they pervade its whole substance, and finally a peripheral clear zone is 
abil ed (2). The substance of this zone then moves to the poles, forming a “ polar 
plate,” while the granules egate in vertical lines, and fuse more and more towards 
ator to form an equatorial plate of microsomata (7). Then SSO, 
begins n, and the daughter-microsomata move apart towards the s (m). On 
their way they form a continuous plate or zone of very minute anhi (2), but 
sometimes the groups may be shown to be still distinct, as at o, which also shows the 
polar stars (“ so) raying out from the protoplasmic cap. The microsomata are 
received and absorbed by the polar plate in a rosette-like figure (2). The polar ana 
invaginates like a gastrula, while the spindle constricts; the polar masses of pro 
w down on the sides (g), and are at last jamn constricted to serve as 
an envelope for the daughter-nuclei ; the spindle-fibres are absorbed into the cavity 
of the gastrula-like “ calotte,” and a stage-like 4 results. The substance of these 
brils is probably that which is separated from the nucleolus to form the paranu- 
cleolus. 
Fic. 104, a-c. A nucleus of Opalina ranarum—Nussbaum, A. m. A., xxvi.—The 
nucleus divides by first forming four “ microsomata nucleoli,” seen in polar view in 
a. ese microsomata divide and move along fibres to the poles, as in 4, and simple 
constriction, as in ¢, and reversion to uninuclear condition follows. 
oo 105, a-f- A ikii of Opalin m. According to Wisenes: (M. J., xi.), 2 
shows an irregular reticulum or “ inet” with a couple of nucleoli and irregular 
masses of chromatin at the surface. In 4 the chromatin has become aggregated in 
superficial microsomata. These are forms of resting nuclei. The initial condition 
from which division p ds is seen in c. We have an abundant knäuel and a few 
nucleoli; then ind the knauel (skein) filament segments ; next, in z, the segments 
are concentrated to the centre. The nucleoli may or may not be absorbed. Now 
there ray out fibres from an “ amphiaster”’ towards the centre from two opposite 
the segments of nuclein arrange themselves into an equatorial plate (/), 
<- and, splitting each into two, send the regular number of V-shaped loops along the 
ae fibres of the spindle to the poles (s4). AS follows (7), and the segments 
"once more fuse into a “ skein-filament” or a “ reticulum.” BEE oe 
cated a form of karyokinesis as psies ROT 
Secs 106; pa Nucleus of embryonic e = Scorpion—Blochmann, M. J.,x.—To 
show “ direct” atoé; the nucleolus then divides, 
next the nucleus does so, and at {last the cell constricts jecol to 
> “Fis. 107. Nucleus of Vorticella in division—Camnoy, p-217-—Shows a simple con- 
t modification of the net-work. — n 
