Cytology and Movements of the Cyanophycea. 299 



ing towards a karyokinetic stage, but that in some cells it 

 does not reach as advanced a condition as in others. 



In those cells where the spireme segments or chromo- 

 somes are formed, each segment or chromosome seems to 

 act independently, though all divide at the same time. 

 When the daughter chromosomes separate, each retreats 

 to its end of the spindle and there begins to diffuse, there 

 being as many such centers of diffusion as there are chro- 

 mosomes. These centres gradually merge together and 

 form the granular nucleus out of which is to form the next 

 net-spireme of the next division, or the chromatin vesicles 

 of the resting stage. 



(4) Protoplasmic Continuity. 



The Cyanophyceas have usually been looked upon as com- 

 posed of groups of cells, but with no connected organiza- 

 tion. As will be seen by the review of the literature, some 

 investigators have been able to find pores in the division 

 walls of these organisms, through which delicate strands of 

 protoplasm passed connecting one protoplast with the other. 

 To Borzi is due the credit of having developed this fact to 

 the greatest extent. He found that the protoplasts were 

 usually connected by means of these protoplasmic threads, 

 but that the heterocysts, which showed the most evident 

 openings were connected to the other cells by means of 

 cyanophycin threads. This protoplasmic continuity between 

 the cells, Borzi concluded, assisted the plant to correlate its 

 movements. This is certainly a logical conclusion, and one 

 that is supported by observation. The evident passage of 

 material from which to form the spores, from cell to cell 

 through these openings, is still stronger evidence of the 

 concentrated organization' of these plants. Macfarlane 

 (51) considered that in the higher plants, sex- forming 

 products might pass through these pores from cell to cell 

 and thus correlate and epitomize the hereditary substance. 

 Gardiner held that ferments and soluble materials passed 



