474 Woolery.—Meiotic Divisions in the Microspore 
granules change in the chromatin thread. Lawson (T2) says that ‘ although 
threads may appear vacuolated, granular, or even beaded, they are composed 
of uniform material As the nucleus prepares for the activity of the 
division to follow, the lumps in the thread appear to become somewhat 
larger and to elongate so that each joins with its neighbours (Fig. 3). 
Some of the thin linin threads which appeared to stretch across to other 
portions of the chromatin now appear to be drawn in and to help make the 
thread appear somewhat wider. Fig. 4 is taken from a section cut 5 microns 
in thickness and portions of the chromatin network are shown. Fig. 5 is 
a portion of another nucleus in which the chromatin granules are more 
evenly distributed along the thread, and it has more the appearance of 
a continuous thread than of a network. In some places portions of the 
thread lie almost parallel with each other. In one place two portions seem 
to be joined together by a slight attenuation of one thread, but it cannot be 
said with certainty that this indicates any pairing which will persist. The 
chromatin thread here is becoming slightly contracted. 
The mother-cells, during the resting stage, are closely packed together 
and have thin walls and uniformly dense cytoplasm. From one to three or 
four nucleoli are seen irregularly placed in the nucleus, in among the 
irregular chromatin thread. The nuclear membrane appears as a sharp line 
separating cytoplasm from nuclear contents. The enlargement of the nuclear 
cavity, which takes place about this time, is doubtless coincident with an 
increase in the amount of containing fluid as Lawson (T 1 A and T 2 ) shows, 
but there is also, at this time and following it, a shortening and thickening 
of threads and a contraction which results in the diminution of the chromatin 
mass. 
Synapsis. Measurements were taken of nuclei in the resting, synaptic, 
spireme, and segmented stages, and the results that were found do not sub¬ 
stantiate Lawson’s theory (’ll A and T 2 ) that the nuclear cavity enlarges 
but the chromatin mass remains stationary in volume. The measurements 
show an increase in the size of the nuclear cavity just preceding and during 
synapsis, which size remains relatively stationary during the spireme and 
segmented stages ; but unquestionably a decrease in the size of the chromatin 
mass is found in synapsis. In taking measurements nuclei were chosen at 
random, care only being taken that the section should be cut as nearly 
through the centre of the nucleus as possible. Of the nuclei measured, the 
average for the resting stage was 16 microns by 14 microns. Nuclei in the 
synaptic state were measured, with an average size of 23 microns by 18 
microns, while the chromatin mass from these same nuclei gave an average 
measurement of 13 microns by jo microns. The two dimensions denote 
the greatest and shortest diameters of each nucleus or mass. The measure¬ 
ments of the nuclei in spireme and segmented stages show sizes tallying 
with the measurements of the nuclear cavities of nuclei with chromatin in 
