CYTOLOGY 207 



bright contrast for the detail (Fig. V.4, .4 and B). A nematode was 

 seen best with 5B — 0. IX and 0.2A +0.25X diffraction plates in the 16-mm 

 objective (Fig. V.4, F-H). Chitwood (1949) found the phase micro- 

 scope helpful in his revision of the nematode genus Melodiogyne. The 

 hooks on an acanthocephalid showed about equally well with the A4- 

 and the B — plates. Penetration glands in trematodes were investigated 

 with phase by Reid (1948). Small insects and insect parts may be 

 examined with the phase microscope, and the high bright-contrast 

 plates may facilitate seeing details or finding the parts as contaminants 

 in food. Gregoire and Florkin (1950) examined plasma coagulation of 

 insect plasma. 



Either the 0.2A+0.33X or the 0.2A-0.25X diffraction plate shows the 

 annulae of fish scales, whereas the J5 — is not so good for this application. 

 A lower magnification than the 16 mm would be desirable for the larger 

 scales. The same phase plates could be utilized for replicas from the 

 scales. 



The bat wing is only about 20 /x thick, too transparent for brightfield 

 microscopy. Howe\'er, when mounted with paraffin oil between glass, 

 it shows considerable detail under the phase microscope. Low and 

 medium contrast A± diffraction plates proved useful at all magnifica- 

 tions. With long-focus condensers and suitable mounts, all magnifi- 

 cations of phase may be useful on transparent chamber preparations 

 for the study of regenerating tissue and atypical growth. B— plates 

 should be tried, as they are often better for these preparations. Details 

 from higher animals will be discussed in following sections. 



4. CYTOLOGY 



The phase microscope shows detail in unstained, salivary gland 

 chromosomes (Fig. V.5) (Michel, 1941. 1950; Richards, 1947c; Schultz, 

 1947). Slight staining with light green gave somewhat better results, 

 according to Schultz. Pollster and Leuchtenberger (1949) found 

 purified methyl green specific for desoxypentose nucleic acid, and this 

 staining might be used with phase microscopy. The effects of digestion 

 and of electrolytes on chromosomes have been seen with phase micros- 

 copy by Kaufmann (1949). Salivary gland chromosomes of Chirono- 

 mns were figured by Barer (1947a). Ludford et al. (1948) compared 

 findings with ultraviolet microscopy and observed chromosome behavior. 

 Michel's (1941) phase motion picture film of cell division in the grass- 

 hopper set a new level for cytological study (Duryee, 1948). 



For chromosome study the 0.14A — 0.25X dark contrast has been pre- 

 ferred, probably because it more nearly resembles the picture seen with 

 stained material. It is possible to see chromosomes in dividing cells in 



