46 Papers from the Marine Biological Laboratory at Tortugas. 
cause of the loss of chromatin from the spherules. The yellow nucleolus 
seen after staining with orange G and Lyon’s blue must be explained, I be- 
lieve, on the assumption that here only the plastin element of the nucleolus 
took a stain, the chromatin element showing no affinity for either of the 
stains employed. That the nucleolus should select one cytoplasmic (acid) 
stain and the remainder of the odcyte another, remains inexplicable. Nor 
does it appear whether the selection is a chemical or a physical phenomenon. 
Chromatin appears to be transported in a highly fluid form through the 
‘nuclear reticulum, where some of it becomes condensed as karyosomes, and 
some carried to the nucleolus, where it is lodged in the form of spherules. 
Here the chromatin undergoes further elaboration and condensation and is 
thus imbibed by the plastin, leaving vacuoles more or less emptied of fluid 
chromatin. Thus the fact that in all living eggs the nucleoli appear vacuo- 
lated is explained by the reasonable assumption that plastin and fluid chroma- 
tin in the shape of spherules have different indices of refraction, due to a 
difference in degree of condensation and possibly of chemical composition. 
When all the spherules are filled and all the chromatin is approximately at 
the same stage of elaboration (as at the culmination of the growth-period) 
the nucleolus stains homogeneously black with iron hematoxylin. When 
some of the spherules have lost their contained chromatin through extraction 
by the plastin, real vacuoles appear which seem colored according as the 
underlying plastin is stained. Whenever the plastin of the nucleolus be- 
comes freed of the chromatin elements it always stains similar to the linin 
of the nuclear reticulum. 
Occasionally one finds full-grown odcytes which contain besides one large 
nucleolus several smaller accessory nucleoli scattered through the nuclear 
reticulum (fig. 56). I have counted as many as fifty of these in odcytes in 
which the chief nucleolus was of almost normal size. Most of these were 
chromatic and stained similar to the chief nucleolus. Evidently such odcytes 
have a superabundance of chromatin. I have never seen any such odcytes 
mature. Cases of such eggs observed by me are too rare to permit the gen- 
eralization that an unusually great amount of chromatin is detrimental to 
maturation and normal development. There is evidently a slight variation 
in the amount of chromatin contained in different odcytes of the same 
individual, but a limit is probably reached beyond which a greater amount 
is abnormal. These cases, however, give certain evidence that the chromatin 
may manufacture plastin, or at least compel the morphological arrangement 
and chemical modification of plastin (linin) to be used as ground-substance, 
for it was frequently possible to see that these accessory nucleoli had each a 
plastin ground-substance, and occasionally one was seen with vacuoles similar 
to those of the chief nucleolus. Again, when the female pronucleus is 
formed it always contains a plastin nucleolus (plasmosome) (figs. 82, 83, 
84). Very rarely this was seen to be chromatic (fig. 81), which may mean 
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