Centrifugal Force upon the Cell. 329 
through them, just as a small glass bead may be made to fall 
through a column of soap-foam. 
As the lamellae are laid bare by means of the centrifugal 
force, thus enabling an unobstructed view of the interior of 
the cell, a word further as regards its structure may not be 
out of place here. 
As is well known (Strasburger, ’97), these lamellae may be 
distinguished in normal cells of Cladophora not too rich in 
chlorophyll. Upon them are usually distributed nuclei and 
chloroplasts. When the movable cell-contents are removed, 
the lamellae appear rigid, forming sharp angles with each 
other like so many cell-walls ; in fact the cell looks as if it 
were filled with a thin- walled parenchymatous tissue. The 
lamellae shift their position little or not at all. On careful 
observation with high powers or oil-immersion, they are 
seen to be in a constant vibrating or quivering motion, and 
over their surface a thin layer of colourless cytoplasm is 
seen to move. It cannot be unreservedly stated that the 
lamellae quiver or vibrate constantly, but this movement was 
seen at each observation. 
Immediately the preparation is taken from the centrifugal 
machine, the displaced contents begin to redistribute them- 
selves, but, in Cladophora especially, very slowly, requiring 
often three weeks for a complete redistribution. During the 
first twenty-four hours the redistribution takes place more 
rapidly, after which it becomes slower and more uniform. 
The time of redistribution will vary with the size of the cell, 
being less in small narrow cells. 
Fig. 1 was drawn twenty- four hours after the centrifugal 
action, when a portion of the chlorophyll and other inclusions 
had advanced somewhat into the colourless part of the cell. 
In the beginning all the movable contents occupied the space 
indicated by the densely shaded portion of the cell. As 
a rule the chloroplasts, and presumably the nuclei also, travel 
back toward the opposite end in a tolerably uniform layer, 
only a few isolated chloroplasts proceeding faster. The 
plastids and nuclei, together with the more coarsely granular 
