214 J- McA - KATER. 



During the early part of the work the cultures contained in 

 addition to Polytomella, Glaucoma scintillans, Chilomonas para- 

 mecitim, Euglena gracilis, Bodo sp. and some mold, but after 

 several months everything disappeared except Polytomella and 

 the mold. Zumstein's medium showed only E. gracilis mold, and 

 Polytomella citri, the acidity of this solution being too great for 

 the others. 



The active forms were fixed in hot Schaudinn's fluid and 

 stained in hot iron-alum-haematoxylin. Methyl green and Dela- 

 field's haematoxylin were also used, but with rather poor results. 

 For counterstaining Bordeaux red, eosin, methylene blue, and 

 orange G were employed, the first two yielding by far the best 

 results. Eosin was used in the 95 per cent, alcohol, while when 

 Bordeaux red was the counterstain the slides were placed in a 

 o.i per cent, solution of the dye for twenty-four hours, immedi- 

 ately after applying the haematoxylin. Bonney's triple stain was 

 tried, but was found to have little value for this work. 



Most of the preparations were made by pipetting a drop of the 

 culture fluid onto a slide, which had been previously smeared 

 with a little albumen fixative, permitting this to evaporate until it 

 did not run and then dropping slide in Schaudinn's for two 

 minutes. Although this technique was quite successful even 

 better results were gotten by centrifuging the material and fixing 

 before pipetting onto the slides. 



It was found that the encysted forms did not fix well in 

 Schaudinn's nor was it possible to get them to take any kind of 

 stain, even aceto-carmine failed to leave any trace of color. The 

 successful technique finally developed was fixation in Bouin's or 

 McClung's modification of Bouin's for from twelve to twenty-four 

 hours, followed by dehydration and imbedding in paraffin. 

 Sections were cut from two to four micra thick, and stained as 

 above. Schaudinn's fluid was tried in place of Bouin's, but 

 usually resulted in shrinkage of the protoplasm away from the 

 cellulose wall. 



MORPHOLOGY. 



Polytomella citri is a colorless flagellate of pyriform shape, the 

 anterior end being rounded, the posterior rather bluntly pointed. 

 The size varies from 14 by 10 micra to 10 by 7, while the average 



