CELL-DIVISION. 33 
left, whose elements diverge, meeting the concave plasma membrane 
at different points. Other delicate fibers extend from the spirem in 
all directions toward the plasma membrane. As soon as the nuclear 
membrane appears these radiating fibers become more uniformly dis- 
tributed about the nucleus. They undoubtedly take part in the forma- 
tion of the spindle in the division of the daughter nucleus. 
FREE CELL-FORMATION. 
The most beautiful and best known illustration of typical free cell- 
formation is found in the development of the spores in the ascus of 
certain Ascomycetes as described by Harper. 
The delimination of the spores from the cytoplasm in Zrysiphe fol- 
lows immediately after the close of the last of the three successive nuclear 
divisions which furnish the eight nuclei for the spores. The entire 
process is accomplished by those kinoplasmic fibers which constitute 
the polar radiations of the last nuclear division and in-a manner quite 
peculiar to asci. 
All of the eight nuclei pass through the anaphase at the same time, 
and, when in the resting condition, cannot be distinguished one from 
the other, with the exception of those that lie close to the wall. The 
polar radiations persist in connection with those nuclei that form 
spores, while from those which do not the radiations disappear entirely. 
The chromatin lies mostly free in the nuclear cavity, but it is always 
in communication with the nuclear membrane, especially near the 
centrosphere (Fig. 12, A). As the first indication of cell-formation, 
the nucleus becomes pointed and develops a beak-like prolongation on 
the side next to the pole or centrosphere. This point or beak gradually 
elongates, so that the centrosphere becomes farther removed from the 
body of the nucleus (Fig. 12, B). As soon as the beak reaches a 
length which exceeds slightly the diameter of the nucleus, its growth 
ceases. This beak consists not of a single fiber or thread but of a 
slender cylindrical tube arising abruptly from a rather broad base. 
Into the tube there extends quite to the centrosphere a continuation of 
the chromatin net, by which the latter remains in communication with 
the centrosphere. In the base of the beak the nuclear network is 
loose and more open, while in the slender part it is drawn out into a 
single and twisted thread. ‘ 
As soon as the beak has reached its definitive length the kinoplasmic 
radiations undergo a remarkable change. The radiations which have 
a direction similar to that of the beak begin now to bend or grow 
backward, with the centrosome as a center, toward the nucleus, so that 
