464 Smith. — Cy to logical Studies in the Protococcales . I. 
grow towards the centre. These furrows are broadly V-shaped and not 
narrow as Harper has shown them for Synchytrium ( 3 ). That this broaden- 
ing at the outer end is the normal condition, and not due to plasmolysis, is 
shown by the fact that the protoplasts are not separated from one another 
by spaces of any considerable width along the transverse cleavage planes. 
At other times the secondary furrows are not formed at right angles to the 
primary cleavage planes but are formed at varying angles (Fig. 4). With 
the completion of the formation of these furrows the protoplasm is divided 
into a number of irregular multinucleate masses with irregular outlines. At 
this time also there is considerable variation in the number of nuclei in each 
protoplasmic mass. The fact that there is no division of the pyrenoid accom- 
panying the cytoplasmic cleavage is much more marked after the longitudinal 
cleavage furrows have been formed. The pyrenoids remain unchanged 
during the process and are still homogeneous in structure with the ring of 
starch plates showing quite plainly around each (Fig. 5). The further steps 
in the process consist in the formation of uninucleate masses of protoplasm. 
The cleavage furrows that cut out these uninucleate protoplasts may be 
formed parallel to the long axis of the mother-cell, although they are usually 
formed at varying angles to the already existing cleavage planes. When 
the process of cleavage has been completed the whole interior of the mother- 
cell wall is filled with angular uninucleate masses of protoplasm (Fig. 5). 
These daughter-cells contain no pyrenoids, the pyrenoids of the original 
mother-cell remaining between the uninucleate cells in certain cases, while 
in others no pyrenoids can be found. The fate of the pyrenoids of the 
mother-cell was not determined, but their disappearance certainly occurs 
after the process of cleavage is well advanced. 
These small uninucleate cells now round up and become zoospores. 
Fig. 6 shows a condition in advance of that found in Fig. 5, the young 
cells having lost their angular shape to a certain extent, but the rounding-up 
process is not fully completed. This figure also shows that a pyrenoid 
reappears in the young cells before the rounding up has become completed. 
At first these new pyrenoids are very minute, red-staining bodies, when 
Flemming’s triple stain is used, showing practically nothing of the hyaline 
area with which they are surrounded when the zoospore is ready for liberation. 
When the process of rounding up has been completed, the zoospores thus 
formed are ovoid or pyriform (Fig. 7), each having a" pyrenoid at one end 
and a nucleus at the other. These two bodies are not always on the line of 
the long axis of the young zoospore as Fig. 17 shows. The relation of the 
cilia to the zoospore could not be determined from the preparations. 
The Growth of the Young Cell. 
Since stages in the liberation of the young zoospores were not observed 
the manner of their coming to rest could not be determined. From our 
