206 PHASE MICROSCOPY IN BIOLOGY AND MEDICINE 



of nuclear behavior has been seen in a small blue-green alga resembling 

 Phormidium. 



Chromosomes and cytological detail in Tradescantia stamen hairs are 

 better seen with the 0.2A+0.25X bright and the 2.5B-0.25X dark 

 contrast, and this may be true generally for plant tissues. The middle 

 lamella and other details in wood sections can be seen to advantage with 

 the phase microscope, with or without staining. Farr (1946, 1949) has 

 used phase microscopy on cotton structure. At present most of the 

 work with these materials has been in the industrial field (see Section 

 10 of Chapter VI). 



3.4. Protozoa and higher animals 



With the larger protozoa different diffraction plates may produce the 

 effect of differential staining. A series showing some of the possibilities 

 with Paramecium hursaria was published by Richards (1947c). The 

 nuclear and larger inclusions show better with low-contrast objectives, 

 whereas the smaller details, cilia, and smaller Protozoa require the higher 

 contrasts. Pigmented regions and symbiotic algae show best with 

 B — diffraction plates in varying degrees of contrast. 



Formation of a mucus-like material and clubbing of the ends of the 

 cilia when locomotion is paralyzed by antisera in sensitized P. hursaria 

 have been demonstrated by Harrison and Fowler (1946). Since 

 colorless and green individuals were used as natural labeling for the 

 sensitized animals, the motion picture showing the reaction was made 

 with color film. Paralysis from serum and the changes following 

 conjugation are visible. Micronuclear changes from ultraviolet radia- 

 tion have been reported by Kimball (1949). 



Large parasitic protozoa, such as Balantidium coli, usually show better 

 with low bright contrast and require increased contrast for the internal 

 details, and small ones like Trichomonas vaginalis need high bright con- 

 trast, although Zinser (1947) found the European dark (A—) contrast 

 useful. Parasitic protozoa will be considered in some detail in Section 

 11. The malaria parasite of the duck shows well with the phase micro- 

 scope (Trager, 1949). 



The cells in Hydra are seen with low bright- or dark-contrast ob- 

 jectives, and the nematocysts show better with the high bright-contrast 

 phase objective. The taxonomically useful details of gastrotrichs 

 showed to advantage with a 0.07A+0.25X bright and a 0.14A — 0.25X 

 dark diffraction plate. Mites, such as Byrohia, are too nearly trans- 

 parent when mounted in Clarite for bright field microscopy but are 

 readily seen with the 0.2A-0.33X or a 0.2A-0.25X plate in the 16-mm 

 phase objective. Similar preparations of Daphnia required the high 



