HEREDITY 



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Fig. 165. — Red-eyed female by white-eyed males, Drosophila melanog aster . 

 The factors for these characters are carried by the X chromosomes. Y chromo- 

 some shown with a knob. In this diagram red is indicated by the symbol W 

 and white by w. The history of the chromosomes is shown in the middle of the 

 diagram. {From Morgan, Physical Basis of Heredity, J. B. Lipvincott Company. 

 By permission.) 



