640 The American Naturalist. [July, 
The time taken to form the figures cannot be determined, but appar- 
ently the various generations of nucleoli follow rapidly, each being 
resolved into the figures and the figures forming granules and the 
granules dissolving into the material that presumably dissolves away 
into the cell protoplasm to help form the yolk. 
The successive generations of nucleoli arise from preceeding ones; 
the first nucleoli come as stated above from the original chromatic 
filament, the following generations arise from the granules, into which 
the nucleoli disintegrate—some granules not dissolving but persisting ; 
later some nucleoli arise from spherules or larger fragments of figures 
that do not break down into the minute granules. In either case the 
new nucleoli arise near the nucleolar membrane; in the first case from 
many granules that become enveloped by a membrane in the second 
case by the union of several spherules or else by the enlargement of a 
single spherule. 
Now the granules are arranged along the plastin network and when 
many combine to form a new nucleolus that nucleolus is a structured 
and complex body having in it a network with granules and an outside 
membrane. Though the nucleolus looks homogeneous yet actual sec- 
tions of nucleoli may show the outside membrane, the plastin network 
and the granules or filaments of chromatin : in fact the nucleolus has the 
same structure as the nucleus. This is seen in section and again when 
the nucleolus passes into the interior of the nucleus to be resolved into 
some complex figure; it may then even come out of its membrane — 
and, as it were, grow out in a tree like net with chromatin on the 
meshes. 
Before speaking of the interesting descriptions of the formation of 
yolk, outside the nucleus, we may venture to restate the above brief 
outline of the process of resolution of nucleoli in comparing it with a 
complex series of pyrotechnic displays. The nucleoli are like most 
complicated fireworks arranged about the periphery of the nucleus— 
apparently simple but complex in internal arrangement. They move in- 
wards towards the centre of the nucleus—as if discharged and then un- 
fold the most diverse stars, feathers, coils, nets, etc., that ultimately 
burst into the smallest sparks, granules, scattering outwards through 
the nucleus along the network of plastin that fills the entire area. 
When most of these sparks are quenched some few are coming together 
near the old point of discharge and fashioning a complex rocket, 
Roman candle, or wheel that will in turn be set off at the succeeding 
display of figures—and so on for several years. 
