134 Wage r. — Observations on the Structure 
into two or more segments. But although indications of the 
above structure are visible, it is impossible to say with cer- 
tainty what is the exact structure of the chromatin body in 
the nucleus in the resting stage. Inside the chromatin is a 
mass of nucleoplasm which does not stain very deeply, and in 
many cases is not distinctly seen owing to the thickness of the 
surrounding chromatin. There is, so far as I am able to 
determine, no nucleolus present. The nucleus is surrounded 
by a limiting layer or nuclear membrane, which can however 
be seen better at a later stage. Rosenvinge 1 has obtained 
nuclei in certain fungi which have a somewhat similar structure 
to the above, but in which no indications of a separation of 
the chromatin into distinct parts was observed. Nuclei which 
have been too deeply stained appear in many cases to be 
perfectly homogeneous. The division of the nucleus in the 
mycelium is indirect, but in badly stained sections, or when 
seen under insufficient magnifying power, the phenomena of 
karyokinesis cannot be observed. In such cases the division 
of the nucleus appears to be direct ; it first elongates, then 
becomes constricted, or dumb-bell shaped, then the connecting 
portion between the two knobs becomes thinner and thinner 
until it finally breaks across, and the two daughter nuclei are 
formed. Karyokinesis when well seen includes all these 
phenomena, but in addition the breaking up and rearrange- 
ment of the chromatin can be seen, when the nucleus is well 
stained, and a sufficiently high magnifying power used. 
The division of the nucleus is preceded by a perceptible 
increase in size and by considerable changes in the chromatin, 
leading to the formation, or separation of it, into distinct 
threads (Fig, 1, 2 , 3 ). In many cases the chromatin appears 
to form granules in the nucleus, but their appearance seems to 
be due to the fact that the nucleus is in such a position as to 
show only the ends of the threads. The threads appear to be 
few in number; they are somewhat elongated, and are arranged 
irregularly. The nuclear membrane can be distinctly seen at 
1 Loc. cit 
