234, A. B. MACALLUM. 
varies in its size and shape, but most frequently it has the 
appearance represented in the figure. 
I have never observed the annular swellings described by 
Balbiani as present in the filament in C. plumosus, but I take 
it that the swollen portions here described are the representa- 
tives of such structures. Nor have I ever determined that 
the filament ends by attachment to the nuclear membrane, or to 
the ameehiform nucleolus, through which it may pass several 
times in its course. The nucleolus varies not only in form 
and size but also in composition. It may be homogeneous, 
but more frequently the central portion contains vacuoles and 
granules and stains more deeply with eosin or safranin, while 
the peripheral non-granular portion may possess no staining 
capacity whatever. In many preparations made from alcohol 
material and stained with eosin, the nucleolar body alone is 
stained, and this is particularly the case when the preparation 
has been treated with acid alcohol and the acid ferrocyanide 
mixture to demonstrate the iron present. The nucleolar sub- 
stance, apart from its granules, contains iron, but the iron 
present is very small in amount compared with that observed 
in the filament, for, when the latter gives an intensely deep 
blue reaction, the colour given the nucleolus is a very pale 
blue, and when the nuclei are kept for a week mounted in the 
glycerine and sulphide mixture in the warm oven, the isolated 
nucleoli develop only a greenish colour, portions of the fila- 
ments, on the other hand, giving in the same preparations a 
marked dark-green reaction. Unlike the differences in staining 
exhibited after treatment with eosin, the faint or light blue 
reaction is uniform throughout the nucleolar substance. 
The dim bands with the excessively fine fibrils in the filament 
are formed of chromatin, as shown by treatment with the stain- 
ing reagents, when the preparations have been properly 
hardened. ‘There is, however, a difference between this chro- 
matin and that of the ordinary animal cell in that while acid 
methyl-green colours the former it leaves unaffected the 
nucleoli and the swollen portions of the filament, which stain 
deeply with hematoxylin and carmine. 
