ii8 



CYTOLOGY 



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I 



CHAP. 



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y.h. 







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B 



4 



x. 



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Fig. 54. 



The chromosomes in the life-cvcle of Phylloxera fallax. (After Morgan, J.E.Z., 1909, and 1915 a.) 

 A, B, polar body formation in a ? -producing parthenogenetic egg : all the chromosomes retained ; L., u, 

 polar body formation in a (^ -producing parthenogenetic egg, showing elhnination of the X chromosome : 

 E, metaphase I., sexual egg ; F, chromosome group from a ? embryo, twelve chromosomes ; G, ctiromosome 

 group from a ^ embryo, ten chromosomes, .vi 



p.b. polar body ; X, the (double) sex chromosome. 



