volume 



400- 



9 300- 



a> 



(T 



200- 



100- 



Figure 11-17. Graph Showing Variations in Volume, Dry Mass, and 

 Solid Concentration of the Cytoplasm of Primary Spermatocytes During the 

 Early Stages of Meiosis in the Grasshopper. (From Barer, R., 1959. "Phase, 

 Interference, and Polarizing Microscopy," in Mellors, R. C. (Ed.), '"Ana- 

 lytical Cytology," 2nd ed., McGraw-Hill Book Co., Inc., New York, N. Y., 

 Fig. 3.16, p. 208.) 



covalent unsaturated groups such as C=C, C=N, C=0, and N=0 in 

 certain organic molecules. Examples of naturally occurring unsaturated 

 covalent groups are the pyrimidine and purine groups of the nucleic 

 acids, DNA and RNA, the bicyclic indole group of tryptophan, the 

 imidazole ring of histidine, and the benzene ring of tyrosine. Because 



SURVEY OF CYTOLOGICAL TECHNIQUES / 237 



