REDUCTION OF VITAL STAINS BY PROTOZOA. 237 



three or four minutes, while Paramecium does not show so 

 uniform a reduction. The dye is retained for a considerable 

 length of time about the food vacuoles and granular substances 

 in the protoplasm. This makes exact comparison of the rates 

 of reduction difficult. But it is evident that the general proto- 

 plasm of Paramecium has become quite colorless at about the 

 time the Opalina has reduced the methylene blue to the leuco- 

 base. This fact makes it improbable that the Opalina has any 

 advantage over Paramecium in its parasitic mode of life in the 

 way of obtaining oxygen for respiration from the decomposition 

 of water. 



In addition to these experiments with Opalina and Paramecium, 

 Janus green of about I to 15,000 dilution was tested out on the 

 protozoa of the intestine of the termite Reticulitermes flavipes. 

 These protozoa ingest the particles of wood which the termite 

 eats. Cleveland (1924) has supplied the final proof that these 

 protozoa are instrumental in assisting the termite to digest its 

 cellulose diet. After a short time the Janus green stains the 

 small particles of wood in the bodies of the various protozoa a 

 light green. If the coverslip is sealed tightly with vaseline, the 

 color changes to pink, and finally to the leuco-base. This 

 suggests the possibility that oxidation of some of the products 

 of digestion of the wood takes place in the vicinity of the food 

 vacuoles, or that oxygen is used in some way in the digestion 

 of the wood itself. 



CONCLUSION. 



Opalina has the power of reducing the vital dyes Janus green, 

 brilliant cresyl blue, Nile blue, toluidene blue, and methylene 

 blue. Paramecium shows similar reduction properties. This 

 shows the presence of a reducase in the protoplasm of protozoa. 

 The wood-ingesting protozoa of the termite's intestine possess a 

 reducase in the food vacuoles, as proved by the reduction of 

 Janus green in these parts of the cell. 



The possession of this reducase is not an adaptation to the 



parasitic mode of life in the intestine where the oxygen pressure 



is low for free living protozoa may also possess it. The results 



are too meagre to state definitely whether the parasitic protozoa 



17 



