Wager . — The Nucleus of the Yeast-Plant . 535 
The nucleolus now begins to divide. Its outline becomes 
slightly irregular, and the deeply stained granular mass 
becomes more prominent. Then an elongation of the nucle- 
olus takes place (Fig. 60), and we have gradually formed 
a long row of granules surrounded by a lightly stained blue 
substance, derived from the nuclear body, stretching across 
the cell either in a longitudinal or a transverse direction (Figs. 
61-63). These granules gradually become separated into 
two groups by constriction, but they remain connected together 
for some time by a less deeply stained substance drawn out 
between them (Figs. 64, 65, &c.). Finally complete separation 
is effected and two daughter-nucleoli are produced (Fig. 68). 
Each one then divides again in the same manner, but in such 
a way that the line of division of one is perpendicular to that 
of the other, so that the two dividing nuclei often present the 
aspect of a cross (Figs. 69, 70 , 72 ). Further divisions may 
take place leading to the formation of as many as eight nuclei 
(Fig. 71 ), but in most cells only four are produced (Figs. 73 - 
75 ). Each of the four nucleoli thus formed becomes 
surrounded by protoplasm and a thin cell-membrane, and 
thus constitutes a spore lying free in the remainder of the 
protoplasm (Figs. 76 - 78 ). The spores are at first very 
small, but they gradually increase in size at the expense of 
the surrounding protoplasm, a thick cell-wall being produced 
around each, until finally they completely fill the mother- 
cell, the wall of which at this stage is in consequence not 
easily visible. They are then mature and enter upon a resting- 
stage. 
The process of nuclear division just described may perhaps 
be regarded as a case of direct division in which the chromatin- 
substance is previously taken up into the nucleolus and 
separated out in the form of granules, which ultimately divide 
into two equal or nearly equal groups. But it may possibly 
be regarded as a very simple case of karyokinesis, if we look 
upon the granules as chromosomes, and the lightly stained 
substance which surrounds them during division as of the 
nature of a spindle-figure. The difficulty of observing all 
