476 Smith . — Cy to logical Studies in the Protococcales. IL 
appearance as those in which it is about to occur, the densely-staining 
chromatin being a conspicuous feature of all such nuclei. 
The formation of uninucleate protoplasts is generally completed by 
midnight. At this time each nucleus lies at one of the angular apices of its 
protoplast. The nuclei are frequently lenticular or curved instead of 
spherical at this time (Fig. 17). The next step in the formation of the 
zoospores is a rounding up and swelling of the protoplasts so that the 
cleavage planes entirely disappear. When this rounding up begins the 
nuclei are even closer to the edge than they were when the protoplasts were 
still angular (Fig. 16). As the cleavage lines disappear the nuclei 
become more dense, but the chromatin granules and the nucleolus are still 
distinguishable (Figs. 18, 19). 
In material fixed at 1 a.m. no trace of cleavage planes could be found, 
but many cells similar to those shown in Figs. 18 and 19 were found 
in my preparations. Cells in the same colony stain differently, so that 
all gradations can be found between those in which there is a heavy stain 
in the cytoplasm and those in which the cytoplasm is only faintly stained ; 
yet in no instance do any cells in this material show signs of cleavage 
planes. The objection might be raised that this condition which I have 
interpreted as a swelling of the protoplasts, making the cleavage planes 
indistinct, comes really before and not after cleavage. However, cells 
