Cytology and Movetnents of the Cyanophycece. 325 



(9) Summary of Results. 



1. The central body of the Cyanophyceae is composed of 

 chromatin and is a true cell nucleus. 



2. This nucleus divides by one of two methods, both of 

 which start upon the karyokinetic history, one going no 

 further than the net-spireme stage where it constricts itself 

 into halves, while the other continues further and forms a 

 rudimentary spindle with rudimentary chromosomes upon 

 linin threads. 



3. In both forms of division, the nucleus divides itself, 

 not being strangled into two parts by the ingrowing parti- 

 tion wall. 



4. The chromatin is arranged on the spireme thread in 

 granules which multiply in number by transverse divisions. 



5. There is no longitudinal splitting of the chromosomes 

 or of the spireme, and in the division of the cell by the 

 method first mentioned above, the two portions of the 

 nucleus are not necessarily equal. 



6. The chromatin is aggregated in hollow vesicles in the 

 resting cell. These vesicles give out their chromatin to the 

 net-spireme very much like the nucleoli of higher plants, 

 and they may represent it. They are imbedded in a granular 

 ground substance. 



7. The outer zone of the protoplast is divided into two 

 portions, a thin colorless ectoplasm lining the cell wall, and 

 the thicker layer between it and the central body. This 

 latter portion contains the pigments which are dissolved in 

 it, and is rightfully termed the chromatophore. 



8. The cyanophycin granules and slime balls are probably 

 food products. They are located in the chromatophore. 



9. The movements of Oscillaria, Cylindrospermum and 

 the other forms of the Cyanophycese which exhibit motion, 

 are caused by delicate protoplasmic cilia distributed along 

 the sides of the trichome. 



10. Finger-like processes of the ground mass of the 



