178 Gardner—Studies on Growth and Cell 
stages of its formation, as one would expect, are very difficult 
to find, for the deeply stained chromosomes obscure the first 
traces of the nucleolus. That the chromosomes employ their 
chromatin to form the nucleolus is easily demonstrable in 
slightly later stages. As the chromosome coil gives up its 
chromatin elements, it loses its dark color gradually. At first 
these chromosomes are full of the dark chromatin granules ; 
these become fewer and fewer as the nucleolus becomes 
larger and more distinct. The chromosome coil or skein now 
appears crimson. Many stages can be found (Figs. 17, 18, 
19), where a few deeply stained chromatin granules can still 
be seen in the thread. 
Finally nearly all the chromatin is passed from the crimson 
thread to the nucleolus. The thread soon loses its evident 
connection with the nucleolus, and spreads out to form the 
nuclear reticulum. The nuclear membrane reappears during 
the time the nucleolus is being formed. When the nuclear 
membrane reappears, the first traces are always on the outer 
poles of the differentiating nucleus. 
Often instead of forming one nucleolus, the chromosomes 
empty their contents so as to form two nucleoli (Fig. 19). 
The two nucleoli may fuse before the resting stage is reached 
or as perhaps more frequently occurs, they never fuse, but 
exist as two nucleoli in the resting cell. 
The daughter nuclei becoming complete, division of the cell 
is completed. This occurs by a pushing in of the protoplasm 
from the two opposite walls of the cell until these inpushings 
meet in the center. The spindle becomes fainter and gradu- 
ally is lost. The division wall becomes distinct, the daughter 
nuclei perfectly formed and division is complete. 
Function of the Nucleolus—¥rom the above observations 
it is impossible to regard the nucleolus as a nutritive centre. 
The nucleolus is, at least in large part, a mass of chromatin 
material, packed together in a rounded form, during the resting 
