290 Allen . — The Early Stages of Spindle- Formation 
Often the nucleole becomes by this means the centre of 
a system of radiating fibres, as is shown at a later stage in 
Fig. 2. The only visible structure in the cytoplasm in the 
earliest stage is a fibrous network. The apparently empty 
meshes are of varying shapes and sizes ; in general they are 
smallest near the nucleus and increase in size toward the 
periphery of the cell. Scattered about upon the fibres and 
between them are granules, staining blue like the fibres. These 
granules are probably, in large part at least, cross-sections of 
fibres, and they are no more numerous than such sections 
would be likely to be in such a network. Often they are 
shown by focusing to extend through the thickness of the 
section. 
Fig. 2 is from material gathered and fixed March 15 ; the 
fixation is according to Vom Rath’s picric-acetic-osmic acid 
and platinum chloride formula. There has evidently been no 
great change during the winter. The Vom Rath fixation, 
however, does not permit of so good a differential stain as the 
Flemming, and the preparations are in general not as satis- 
factory. The fibrous network is still present, though not well 
brought out ; between the meshes, especially near the nucleus, 
is a granular or cloudy substance, but the large peripheral 
meshes are still empty, giving the outer part of the cell a 
vacuolated appearance. In the cytoplasm are seen occasional 
small rounded bodies of distinct outline, staining homo- 
geneously and a little more deeply than the rest of the 
cytoplasm. 
Fig. 3 shows a somewhat later condition (in Flemming 
fixation, as are all the remaining figures). The cells have 
now rounded up and are provided with a relatively thick 
cell-wall. The blue intercellular substance has disappeared, 
and the cells float in a colourless liquid. The cytoplasm now 
plainly contains two constituents, the fibrous meshwork first 
observed, which stains blue, and a cloudy or very finely 
granular, orange-staining material. The latter substance does 
not occupy all of the inter-fibrous spaces, but clear areas of 
varying size are also scattered through the cytoplasm. Some- 
