STUDIES ON PARAMECIUM. 



6 9 



RESULTS. 



Certain dyes did not stain the cytoplasm of normal living 

 Paramecium (Table I.). Of the colors tested, these were anilin 

 blue, alizarin, erythrosin, orange G, Lyons blue, purpurin, eosin 

 Y, trypan blue, trypan red, and congo red; all of them except 

 Lyons blue belong to the acid group of dyes. With these stains, 

 color became visible in the cytoplasm only when the animals 

 were dead or moribund. Dead animals usually stained almost 

 immediately even though the cell membrane was not broken. 

 The macronucleus of the dead organisms was stained by all of 

 the dyes except erythrosin and orange G. In some instances, 

 the cytoplasm might stain before the animal was entirely dead, 

 but such paramecia were always swollen and sluggish, and very 

 obviously moribund. Except in purpurin or in eosin, the Para- 

 mecium could live normally and apparently indefinitely in any 

 of the above dyes as long as the cytoplasm did not stain. 



TABLE I. 



DYES NOT STAINING CYTOPLASM OF NORMAL LIVING Paramecium. 



(C. & B.) = Coleman and Bell Co. 

 (G.) = G. Grubler and Co. 

 (M). = H. A. Metz and Co. 

 (N.) = National Aniline and Chemical Co. 



Purpurin, which has been used as an indicator for calcium in 

 dead Paramecium (Sampson, 1925), does not stain any part of 



