Cytology and Movements of the Cyanophycee. 263 
almost free from granules. A small quantity of a chro- 
matin-like substance was found in it, which resisted diges- 
tion with artificial gastric juice. This material contained 
phosphorus and “masked” iron, and was uniformly diffused 
throughout the cytoplasm of the central body. The proto- 
plasm of the peripheral layer was always more coarsely vesic- 
ulated than the central body. There were usually two types 
of granules present, one set which stained with hematoxylin, 
and contained “masked” iron and phosphorus and therefore 
resembled chromatin, but which became dissolved by arti- 
ficial gastric digestion. These, which he called “granules 
of the first type,” were hollow when they became large and 
divided at the time of cell division. They were usually 
found in the peripheral part of the central body, though they 
might extend to its central part or to the inner portion of 
the peripheral cytoplasm. The “granules of the second type” 
were found in the outer protoplasm and chiefly adjacent 
to the cell membrane. They rarely took the form of hollow 
spheres. They stained deeply with picro-carmine, had no 
organic phosphorus or “masked” iron, and dissolved very 
quickly in weak acids. They were probably of a proteid 
nature. The heterocyst was a degenerated cell in which the 
distinction between central and peripheral parts was lost. 
The chromatin-like substance of the central body diffused 
throughout the cytoplasm when the heterocyst was formed. 
When fully developed, the cytoplasm gave a feeble reaction 
for iron. A small mass at one or either pole of the cell gave 
a distinct reaction for “masked” iron and stained deeply 
with picro-carmine. As it did not dissolve in acids it was 
not related to the granules of the second type. He thought 
that the formation of the heterocyst next to the spore in 
Cylindrospermum majus and other forms, as well as its 
development beside the cells out of which arise the lateral 
branches in Tolypothrix, would appear to suggest that it 
might be the result of some rudimentary sexual process. He 
believed that there was no cell nucleus nor any structure 
