292 KOFOID AND SWEZY. 



in the stain for the same length of time or longer. For very good 

 chromatin staining one hour gives better results. After staining, 

 decolorize in iron alum and wash in 50% alcohol for two hours, or in 

 water. 



Intra vitam stains such as neutral red, methylene blue N, and new 

 methylene blue G G were used. Neutral red prepared with normal 

 salt solution gave best results. 



For examining the living flagellates the cover-glass was sealed with 

 vaseline, after diluting the intestinal smear with normal salt solution. 

 All of the Protozoa common in the intestine have been kept alive 

 in this manner for about 24 hours, and in the case of Trichomonas 

 augusta, which is apparently the most resistant form, individuals 

 have been kept alive for several months without any change in the 

 medium, or removal of the cover glass. Other species of Trichomonas 

 have been kept alive for days or even a few weeks in the same manner. 

 Hanging drop preparations were tried but were not successful, the 

 protozoans dying within a very short time. Cultures were made by 

 placing a bit of the intestinal contents in a hollow ground culture 

 slide, filling the cavity with normal salt solution and sealing down the 

 cover glass with vaseline. Trichomonads have been kept alive in 

 these cells for six months with no apparent degeneration in the or- 

 ganisms. Cultures were also made by placing some of the intestinal 

 contents in small Stender dishes with a quantity of normal salt solution, 

 and also with sterile earth and boiled water from infusions. Most of 

 the parasitic protozoans could be cultivated in this way for a few 

 weeks and would then disappear. Ringer's solution was tried as a 

 culture medium but results were not so successful as with normal salt 

 solution. Cover glasses may be floated on the surface of these cul- 

 tures and removed at any time for examination, and when the adherent 

 flagellates are present they may be fixed and stained in the usual way. 



For searching preparations and recording the location of division 

 stages a mechanical stage with verniers has been indispensable and 

 for the analysis of the finer structure a 100 watt Mazda lamp has 

 been used as the source of illumination, and Zeiss apochrom.atic 2 mm. 

 objective with Nos. 12 and 18 compensating oculars and Watson's 

 new No. 20 holoscopic eyepiece to secure the desired definition and 

 magnification. 



We will now proceed to the discussion of mitosis and multiple 

 fission in four of the representative trichomonad flagellates, Tricho- 

 monas augusta Alexeieff, T. muris Hartmann, Eutrichomastix ser- 

 pentis (Dobell), and Tetratrichomonas proivazeJci (Alexeieff) treating 



