490 



GENETICS OF SOMATIC CELLS 



too effectively as a destaining agent, thereby leaving the chromosomes only faintly 

 stained. Whenever major spiralizations of the chromonemata become evident at low 

 magnification after destaining, some control over this step is warranted. The use of 

 the stain prepared secondarily will help greatly whenever the cytoplasmic staining 

 must be corrected prior to squashing for better phase-contrast observation. 



Fig. 68. Layout of chemicals and instruments for preparation to demonstrate 



CHROMOSOMES. 



6. Invert cover glass onto siliconed microscope slide and pass over a low flame 

 several times. Press firmly and heavily — without any side motion after placing the 

 slide in the center of a bibulous pad. Use fingers of both hands to cover area of cover 

 glass. 



7. Observe slide under the microscope. In the event cells appear fully rounded 

 and dense, it generally indicates : (a) the presence of too many neighboring cells or (b) 

 insufficient pressure applied to the pad. Remove slide from the microscope and add 

 a few drops of the dilute (0.5 per cent) acetocarmine along the edges of the cover glass, 

 pass over the flame several times, and press again under the pad, but this time, place the 



