3L 



&■* '' * ft. ■ 



»*"t^.. 



B C 



Plate 3. A shows the chromosome complex from a salivary gland nucleus in 

 Drosophila melanogaster. Notice that similar chromosomes are paired, and the 

 inert regions united into a single chromocentre (upper middle, just below the 

 small IVth chromosome), so that the V-shaped llnd and llird chromosomes each 

 have the appearance of two long arms (2 right and 2 left, 3 right and 3 left). 



(Courtesy of B. Kaufmann.) 

 B shows loop pairing in an inversion {CIS inversion) in the X-chromosome of 

 D. melanogaster, as it appears in salivary gland nuclei. The chromocentre is below. 



(Courtesy of M. E. Hoover.) 

 C shows a "lamp-brush" chromosome from an oocyte of the newt Triturus. 

 The chromosome, which is unstained, is being stretched between two micro- 

 needles. Notice the chiasmata. The preparation is from a fairly late oocyte stage, 

 in which the chromosomes have already lost much of their fuzzy appearance. 



(x 100. Courtesy of W. E. Duryee.) 



