McAllister . — Nuclear Division in Tetraspora lubrica. 687 
may possibly be the explanation of Golenkin’s results with Hydrodictyon 
and Sphaeroplea. 
In the early prophases the net knots become more conspicuous, — 
increasing in size until the chromatic granules are conspicuous blue-staining 
bodies many times the size of the original knots, and apparently of uniform 
size. Accompanying this increase in size there is an apparent decrease in 
the number of the net knots. Figs. 4 and 6 show stages in the develop- 
ment of these bodies. Notwithstanding these marked changes in the 
nuclear contents the reticulate condition persists in nuclei which have 
relatively large chromatin bodies (Fig. 5 ). 
The nucleole apparently remains unchanged during the period of 
increase in chromatic material. Fig. 6 shows a nucleus in which the 
chromatic material is nearly at the stage of spireme formation while the 
nucleole is still intact. It seems perfectly clear that the nucleole does not 
here undergo disintegration during the increase of stainable material in the 
nuclear cavity. It does not disappear until the spireme material is all 
formed, — therefore any participation by the nucleole in the formation of 
the spireme thread must be very slight indeed. 
The uniform chromatic bodies of this much modified reticulum ap- 
parently become arranged side by side or in a row to form the spireme 
thread, which, although at first appearing to be of irregular diameter, does 
not seem to be made up of definite ‘ chromomeres ’. If this spireme is ever 
in a uniformly distributed condition throughout the nuclear cavity, it remains 
so distributed for but a very short time, for nearly all of the nuclei con- 
taining the unsegmented spireme show the thread somewhat contracted to 
form a loose aggregation occupying the central part of the nuclear cavity 
(Figs. 7 and 8 ). 
A stage possibly similar to this has been described by Davis (12) as 
occurring in the prophases of dividing nuclei in germinating spores of 
Pellia. Here the chromatic material becomes more or less grouped around 
or near the nucleole in a loose aggregation, which does not entirely fill the 
nuclear cavity. 
Stout (44) has also called attention to such an aggregation of the 
chromosomes in the nuclei of root tips of Carex. He says, — “At one stage 
in the late prophases the chain of chromosomes is tightly coiled about the 
nucleole.” 
It is my opinion that no especial significance is to be attached to this 
contracted condition. The more or less connected condition of the chromo- 
somes as late as the metaphases suggests that even during the spireme stage 
somewhat of a reticulate condition still exists. If such were the case, the 
uniform distribution of the spireme would probably be much restricted. 
Upon the segmentation of the spireme, the chromosomes come to be 
quite widely separated from one another, causing this to be a conspicuous 
