Effect of Gentian Violet on Protozoa. 121 



dye was investigated in two ways: 1st, by applying it directly 

 to the organism and transplanting to another media and, 2d, by 

 growing the organism in media containing the dye. In the first 

 series of experiments the Paramecium was found to be readily 

 stained and promptly killed. When placed in media containing 

 gentian violet, the effect of the dye could readily be studied on a 

 single organism placed in a watch glass for this purpose. To the 

 fluid in which the organism was swimming gentian violet in a 

 dilution of 1 to 100,000 was added. The effect of the dye was 

 sharp and constant. The nucleus soon became distinctly stained 

 and the cell outline sharply marked out by the staining of the 

 protoplasm. This took place while active motility of the organism 

 was still retained (both rotatory and progressive) and while the 

 cilia were still whipping violently. Before long, however, motility 

 diminished and finally came to a standstill. The cilia continued 

 for some time to wave. After a further interval the movement 

 of the cilia stopped and the organism gradually swelled. Then 

 the cell membrane ruptured, allowing the protoplasm to escape; 

 and the organism either appeared as a deeply stained, motionless 

 and structureless mass, or else persisted only as unrecognizable 

 debris. The effect of the dye was, of course, varied by varying the 

 dilution used. In strengths of I to 100,000, cessation of motility 

 occurred in a few moments. In 1 to 500,000, some of the organ- 

 isms were still motile 48 hours after immersion, but none of them 

 survived. In strengths of 1 to 1,000,000, fission was always 

 delayed and usually prevented, though some of the organisms 

 reproduced slowly, and one which was thought to be faintly stained 

 was seen in the dividing stage. 



There was no question that the nucleus of the Paramecium was 

 in these experiments deeply stained, while both the organism and 

 its cilia were still actively motile; and, if motility be regarded as a 

 certain indication of life, the observations warrant the conclusion 

 that gentian violet is a true, vital, nuclear stain. We were unable, 

 however, to observe cell division in a definitely stained organism; 

 and the motility in these experiments might well be interpreted 

 as a survival phenomenon in a dead or dying organism. The 

 nature of the experiments was, therefore, changed and the effect 

 of the dye on growing animal tissue investigated. 



