294 Phillips on a Comparative Study of the 



acid, but digestion with trypsin in an alkaline fluid causes 

 them to disappear. They are usually scattered throughout 

 the peripheral protoplasm, or aggregated at times along the 

 division walls of the cells. Especially do they take the latter 

 position in Oscillaria. 



Vacuoles. 



Vacuoles have been described in this group by different 

 authors. Hieronymus and Palla declared that they were 

 normal structures, while Gomont and Zacharias claimed 

 equally strongly that they did not occur in active cells. 

 Zukal considered that they appeared upon degeneration of 

 the cell. This is the case in all of the organisms examined 

 by the writer. Vacuoles, as normal structures, do not 

 appear in any of the Cyanophycese. They can be made to 

 appear by cultivating the organisms in darkness or in an 

 unpropitious environment. When they appear as patho- 

 logical conditions upon the breaking down of the cells, they 

 have no tonoplast as described by De Vries (21B) and 

 Went (83), but are merely globules of disintegrated cell 

 substance enclosed in openings within the protoplasm. That 

 they are formed by the disintegration of the protoplasm is 

 plainly evidenced by the presence of oil and other similar 

 products. The vacuoles described by some authors as 

 occurring in the central body, sometimes even filling it com- 

 pletely, are in reality the larger or smaller hollow chromatin 

 vesicles as described above. 



Other Cell Constituents. 



The chemical composition of the various parts of the 

 protoplast has been spoken of in the different sections treat- 

 ing of the organs in detail. There are, however, some sub- 

 stances in the cells of the Cyanophycese, the presence or 

 absence of which have certain bearings upon the interpre- 



