Cytology and Movements of the CyanophycecB. 277 



omes of Cyanophycese to show the effect of the stain upon 

 their nuclei. In every instance the nuclei of Spirogyra and 

 the central bodies of the lower plants would give identical 

 results. After as much was made out from the living 

 preparations as possible, fixed and stained material were 

 resorted to for the purpose of checking and supplementing 

 the former observations. Any point thus noted would be 

 again sought and found if possible in the living unchanged 

 cell. 



But as is well known, fixed material is open to the criti- 

 cism that artifacts may at times be formed. To overcome 

 this it was thought that if several different fixatives sup- 

 plemented by several different stains should each bring out 

 the same features constantly, the strong presumption would 

 be that the structures shown would be natural to the organ- 

 ism, for in such a concert of results, obtained from such 

 different chemicals and fixing methods, there would have 

 to be some natural structure to act as a determining cause 

 or there would certainly be differences shown in the fixed 

 material. All of the experiments here detailed, and the 

 results given, were thus confirmed. 



The Cyanophyceae have usually been quite scientifically 

 investigated, but in the study of the bacteria, where the 

 cells are so much smaller and probably more delicate, some 

 methods have been employed which would not be counte- 

 nanced at all in higher forms, and even such methods have, 

 at times, crept into the investigations of the Cyanophyceae. 



The fixing reagents chosen were chromic acid of various 

 strengths, chromacetic acid, corrosive sublimate — both hot 

 and cold — picric acid, in alcohol and in water, picro-sul- 

 phuric acid, osmic acid, Flemming's strong and weak fluids, 

 Hermann's fluid, acetic acid of various strengths, formalin, 

 alcohol, formalin and alcohol mixed, and boiling in water. 

 Staining was effected with Heidenhein's iron-ammonia-alum 

 hematoxylin, Delafield's hsematoxylin, acid hsematoxylin, 

 saffranin, eosin, erythrosin, methyl green, methyl blue (for 



