IRON COMPOUNDS IN ANIMAL AND VEGETABLE CELLS, 235 
Balbiani! concluded from such results that chromatin (sub- 
stance chromatique) is present, not only in the dim discs, but 
also in the annular swellings and the nucleoli. According to 
Flemming,” safranin colours all these elements, but stains the 
nucleoli very strongly. Flemming’s observation is correct only 
for preparations made with the chrom-osmio-acetic reagent ; 
but when the nuclei have been fixed with alcohol, or with 
corrosive sublimate, treatment with acid alcohol for two or 
three days affects the filament in such a way that its discs and 
their excessively fine fibrils absorb and retain the safranin to a 
very marked extent, while the nucleolus remains unstained, 
and the swollen portions of the filament are faintly coloured. 
It is possible to obtain in such preparations both the safranin 
and the Prussian blue reactions, and then, with the exception 
of the faint blue in the nucleoli, both effects are co-extensive 
and of equal intensity. The marked difference between the 
substance of the discs and that of the nucleoli is thus shown, 
but it may be brought out in a more brilliant way by staining 
Prussian blue preparations with eosin, which then affects the 
nucleolus only. 
The nucleolus thus resembles the similarly named structure 
obtaining in the nuclei of Vertebrates, but it differs from this 
in that it is amoeboid in form, and does not possess, in any case, 
a chromatin envelope. The presence of granules and vacuoles, 
moreover, appears to indicate that it is physically active, which 
cannot be postulated of the vast majority of the nucleoli of 
Vertebrate cells. 
Whatever effects may be obtained by treating the nuclei 
with various staining reagents, but one results in the cytoplasm 
of the secreting portions of the salivary gland in Chironomus. 
Acid methyl-green in the fresh preparations, and hematoxylin 
and safranin in the hardened glands, demonstrate very clearly 
that there is a stainable substance, in many respects like 
chromatin, uniformly distributed through the cytoplasm ; that 
it is chromatin would appear from the fact that the cytoplasm 
} Loe. cit. 
* *Zellsubstanz, Kern- und Zelltheilung,’ pp. 112, 113. 
