628 Wisconsin Academy of Sciences, Arts, and Letters. 
higher magnification the organization of the chromatin into 
threads with a disappearance of many of the fine linin strands. 
As suggested above, the formation of the leptonema spirem 
results from a spreading of the chromatic material of the net 
knots along certain of the strands of the reticulum forming a 
thread into which is withdrawn others of these linin fibers, 
There is no definite arrangement of the knots into rows to form 
the spirem as seems to be the case in the formation of the spirem 
in the earlier mitoses of the anther. The knots of the reticu¬ 
lum placed side by side would, because of their great diversity 
in size, form a spirem of extreme irregularity and, in places, of 
much greater diameter than the leptonema spirem shown in the 
figure. It seems probable that some of the smaller knots lying 
side by side in the reticulum do form a part of a spirem, but 
nevertheless have no especial significance. Figure 9 shows a 
tangential section of a nucleus which lies in an anther with 
other nuclei in advanced stages of synapsis. Strands are still 
present but the appearance of chromatin knots is giving place 
to a condition in which the chromatin is distributed in threads. 
The disappearance of the fine strands of the reticulum together 
with the appearance of more open, free areas in the nuclear 
reticulum certainly suggests strongly the withdrawal of part of 
the fine strands into the knots or into the other strands. 
We must conclude 1 think that the thin chromatin spirem is 
formed by two processes,—first the elongation of the net knots 
in certain definite directions along certain of the connecting 
fibers to form a much attenuated chromatic strand and secondly 
the withdrawal into the aggregation thus formed of the remain¬ 
ing linin strands. 
Almost at the same time that the leptonema spirem becomes 
differentiated, the chromatic content of the nucleus can be seen 
to be irregularly drawn away from the nuclear membrane in 
places (Fig. 7). A tangential section (Fig. 7a) of the same 
nucleus as figured in figure 7 shows that the chromatin is prob¬ 
ably all transformed into the spirem, though certain other areas 
such as are represented in figure 9 still show fine strands which 
indicate that a spirem of uniform thickness has not yet been 
