

Figure 4-20. (a) Drawing Showing the Normal Banded Appearance of 

 a Portion of a Salivary Chromosome (above) and Its Appearance After 

 Formation of a Balbiani Ring (below) at the Point Marked by the Arrows, 

 (b) Diagrammatic Representation of Part of a Helically Wound Bundle of 

 Chromonemata in a Salivary Chromosome at the Location of a Fully De- 

 veloped Balbiani Ring. Hypothetical loop formation of the ultimate chromo- 

 nemata at the periphery is shown. (Fig. (a) from Gall, J. G., 1956. "On 

 the Submicroscopic Structure of Chromosomes," Brookhaven Syinp. Biol., 

 21, Fig. 15, p. 29. Fig. (b) from Beermann, W., 1956. "Nuclear Differenti- 

 ation and Functional Morphology of Chromosomes," Cold Spring Harbor 

 Symposia Quant. Biol., 21, Fig. 6, p. 227; courtesy of Dr. Wolfgang Beer- 

 mann, Zoologisches Institut, Universitat Marburg, Germany.) 



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