No. 466.] STUDIES ON PLANT CELL.— VIII. 699 



view that the cells of the Cyanophyceae and also of the Schizo- 

 mycetes contain nuclei, taking a position in sharp opposition to 

 that of Biitschli ('96). Fischer's conclusions were based on his 

 failure to find that differentiation of the protoplasm within the 

 cell demanded by the conception of the central body and the 

 activities of this structure during cell division as described by 

 other authors. He presented a sharp criticism of the conclu- 

 sions based on the reaction of stains in determining the nature 

 of protoplasmic structures, criticisms largely directed against the 

 investigations of Biitschli. He showed by some ingenious experi- 

 ments upon emulsions of albumen fixed on a slide that stain 

 reactions were a purely physical phenomenon. Thus the same 

 combinations of stains, such as saffranin and gentian violet, may 

 be made to give exactly opposite results in differentiating a mix- 

 ture of large and small globules of albumen when used in reverse 

 order. He attached no importance to the so called affinity of a 

 protoplasmic structure for a particular stain and would not accept 

 such apparent affinity as evidence of its chemical nature. The 

 fact that the central body takes chromatic stains did not seem to 

 him important evidence of its nuclear character and he was very 

 positive in his behef that the cells of the Cyanophyceas do not 

 contain nuclei and that the central bodies should not be consid- 

 ered the phylogenetic forerunners of such structures. 



This attitude of Fischer towards conclusions based on stain 

 reactions was later presented in more elaborate forrn in his cri- 

 tique ('99) on methods of fixing and staining protoplasm and has 

 had an important influence on methods of cytological investi- 

 gation and interpretation. The stain reaction is now regarded 

 as probably merely a physical phenomenon but an effective 

 means of differentiating protoplasmic structures. The deter- 

 mination of their morphology rests with an understanding of 

 their history and behavior in the activities of the cell. Although 

 Fischer's general criticism of methods of cell research was 

 timely and in some instances richly deserved, nevertheless his 

 particular conclusions respecting the cell structure of the Cyano- 

 phyceae and the Schizomycetes have not been sustained by 

 investigators who have followed the history of the protoplasmic 

 structures in the cells of these organisms. 



