Cytology and Movements of the Cyanophycece. 283 



of hollow chromatin vesicles. The fact that these vesicles 

 are often quite large, especially in plants that have been 

 cultivated in solutions which feed the chromatin, had led 

 some observers to consider that they were vacuolated. But 

 their behavior during division excludes the possibility of 

 such an assumption. The central body is of no definite 

 form, its outline being determined by the number of balls 

 within it. In Oscillaria the central body fills up a large por- 

 tion of the width of the cell and in some forms quite as 

 much of the length. In Cylindrospermum the central body 

 is more elongated in the longitudinal axis of the trichome, 

 often reaching from end wall to end wall. By cultivating 

 the organism in a full culture solution for several days, or 

 in a solution strong in soluble phosphates and iron which 

 feed the chromatin, the outer stainable walls of the "chroma- 

 tin vesicles" become much more pronounced, while if cul- 

 tivated in fluids which are poor in these substances and 

 which would thus starve the chromatin they become degen- 

 erated, losing their power to take up chromatin stains. This 

 is quite in accord with the work of Brass (6A) who was 

 able in this way to so starve the chromatin of the nuclei of 

 Amoeba and Gregarinida as to make them quite poor in this 

 element. Digestion of these organisms in artificial gastric 

 juice made the central body much more evident, though it 

 dissolved away the surrounding protoplasm and caused the 

 chromatin vesicles to take a characteristic yellow luster. 

 Experiments upon Spirogyra, carried on in the same culture 

 dishes with the above, gave identically the same results as 

 regards the chromatin. When cultivated in a full nutrient 

 solution, the nucleus became much denser in its staining 

 properties and somewhat enlarged, while when the cultiva- 

 tion was carried on in a solution free from phosphorus the 

 opposite was sure to occur. The central body, of the forms 

 of Nostoc that grow in Collema, or of Anabaena found in 

 the roots of Cycas, is very much poorer in chromatin than 

 is that of similar plants growing under their natural environ- 



