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THE AMERICAN NATURALIST [Vol. XLVIII 



Spread wings in the third chromosome group. Beaded 

 wings have not appeared in the stock bottles of Spread 

 which breeds perfectly true. 



D. Stumpy Wings 

 Becently a new non-lethal sex-linked character has ap- 

 peared in the offspring of the cross of an F 2 Beaded male 

 to a Wild female. Its nature has not yet been worked 

 out, since only males have thus far appeared. The flies 

 have wings resembling those of Vestigial, save that they 

 are not held at right angles to the body, but in the normal 

 position. Vestigial is not a sex-linked character. 



Summaey 



The character under consideration is that of Beaded 

 wings in Drosophila ampelophila. All gradations of 

 form between that of normal wings (Fig. 1) and those 

 shown in Figs. 2 to 12 occur in the stock bottles, though 

 certain selected strains of the stock give no normal- 

 winged offspring. 



When a Beaded fly is mated to a fly of a stock not 

 carrying genes for Beadedness in its germ plasm a vary- 

 ing percentage of the Fj offspring is Beaded. If the male 

 parent is Beaded the majority of the Beaded offspring 

 are usually females ; and if the female parent is Beaded, 

 the majority of the Beaded offspring are usually males. 

 A female Beaded fly however gives a larger percentage 

 of Beaded daughters than does a male Beaded fly. This 

 phenomenon is repeated from generation to generation, 

 no matter whether a given Beaded fly has come from a 

 male or female Beaded parent, and this shows that the 

 phenomenon is not caused by a sex-linked gene. 



This phenomenon is not caused by non-disjunction of 

 a sex-linked gene, for tests of both the Beaded and Wild 

 stocks showed non-disjunction to be a rare phenomenon. 

 The only explanation suggested was that the male off- 

 spring were somewhat influenced to or away from Beaded- 

 ness by the nature of the cytoplasm that was brought in 

 with the egg, while females were not readily influenced 

 in this way. 



