264 A. B. MACALLUM. 
From all this it may be gathered that nuclei, in the strict 
sense of the term, are not present in the cells of the Cyano- 
phyceze, and that if any structure performs the functions of 
such an organ, it must be the colourless central body. In 
regard, however, to the composition, the position, and the 
number of varieties of the granules, there is less of concord- 
ance. All the observations quoted would appear to indicate 
that a typical chromatin substance is absent. If a ‘‘ masked ” 
iron compound is present in these organisms, with what part 
of the cell is it associated ? 
The forms which I used, in endeavouring to determine an 
answer to this question, were: Oscillaria Froelichii, Oscil- 
laria princeps, Oscillaria sp., Tolypothrix sp., Scy- 
tonema sp., Microcoleus terrestris, Cylindrosper- 
mum majus, Anabena (Spherozyga) oscillarioides, 
and Nostoec commune. The fixative reagents used were 
alcohol, corrosive sublimate, the stronger Flemming’s fluid, and 
saturated solutions of picric acid ; while the staining fluids 
employed were hematoxylin (Khrlich’s and Delafield’s), alum 
cochineal, picro-carmine, safranin, and eosin. In determining 
the presence of iron compounds, material hardened by alcohol 
only was used. 
The results of my experiments, so far as they affect the 
question of the relations of iron to the cytoplasm of these cells, 
may be summarised as follows: 
1. The cytoplasm consists of a dense central portion and of 
‘a vesiculated peripheral zone, the former staining with hema- 
‘toxylin, alum cochineal, and safranin more deeply than the 
latter when it is free from granules or vesicles, but when 
vesicles are present they stain deeply, while the remainder 
of the central portion acquires a faint colour only slightly 
more marked than that of the peripheral portion. ‘The size of 
these vesicles of the central portion varies from that, in which 
they appear as scarcely larger than granules, to that observed 
in Tolypothrix sp., in which they measured in diameter a 
third of that of the cell. The stainable substance of these 
forms a thick membrane enclosing an apparently inert sub- 
