Cytology and Movements of the Cyanophycece. 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 haematoxylin, 

 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 



