Cytology and Movements of the Cyanophycecs. 247 



dividing nucleus. This was considered to be a nucleus 

 because it broke up into a number of pieces and the cell then 

 divided, tlie ingrowing division wall being plainly seen. 

 Between the daughter nuclei he could further distinguish, 

 in some cases quite distinctly, fine colorless striae which sug- 

 gested the achromatic fibers of karyokinesis. 



Probably the most extensive worker on the Cyanophyceae 

 was E. Zacharias, to whom we owe much in the solution of 

 the cytological problems, not only of these but of all organ- 

 isms. His researches covered not merely the staining rela- 

 tions of the different parts of the cell, but included an 

 exhaustive micro-chemical study, and it is for this portion of 

 his work that we owe him greatest thanks. His first inves- 

 tigation (88) published in 1887, was on Tolypothrix and 

 Oscillaria and his methods and conclusions might be 

 summed up as follows : First. Fresh material treated with 

 gastric juice, was extracted with ether and alcohol, fol- 

 lowed by 0.3 per cent, hydrochloric acid. The granules gave 

 the characteristic "nuclein luster." Second. In material 

 treated as above, followed by 10 per cent, sodium chloride 

 or with 0.05 per cent, potassium hydrate the "central sub- 

 stance" disappeared. Third. Fresh threads treated with 55 

 per cent, hydrochloric acid caused the "central substance" 

 to swell. These considerations caused him to conclude that 

 the "central substance" was a nucleus. 



In a later work, Zacharias (89) extended his studies to 

 include, besides the former organisms, Nostoc, Tolypothrix, 

 Cylindrospermmn and Scytonema. It was in this work that 

 he took up the micro-chemistry most fully. He found a 

 colored peripheral layer, often thickest on the partition walls, 

 which he thought was surrounded by a thin uncolored 

 plasma layer, and a central part which always remained 

 clear. He could not determine whether the colored portion 

 was to be regarded as a chromatophore or not. In the cen- 

 tral part he saw many granular frame-like formations and 

 one or two nucleolar-like bodies, though they were not pres- 



