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THE AMEBIC AN NATURALIST [Vol. XLVIII 



back-crossed to Pink normal stock, six flies of the cross- 

 over class appear. For reasons to be mentioned, it is 

 improbable that these represent cross-overs, however, but 

 rather they may be due perhaps either to the presence of 

 the second chromosome gene, 1, which usually does not 

 manifest itself in the absence of the third chromosome 

 gene, or to mutation, or to some unknown abnormality. 

 Through carelessness only one of these males was tested 



TABLE XXVII 



or used further in breeding. They were very slightly 

 Beaded, and had only a very slight "nick" at the tip of 

 the wing, even smaller than that shown in Fig. 3. The 

 single Pink Beaded male mentioned in Table XXIX was 

 mated to several females but was sterile. Another test 

 is also possible, and was made as follows. Pink normal 

 males and females from Table XXIX, which of course 

 should not carry the third chromosome gene for Beaded 



TABLE XXVIII 



Repeated Back-crosses of F x Flies of the Cross Pink Beaded X Wild 

 to Pink Flies of Normal Stock 



Fi9XPinko\ TypeX \ 1 228 



Fi9XPinkcf. TypeY 24 379 



Fic?XP9 1 7 I 133 1 I 135 I 3.5 1 3.5 



wings, were then mated together, and among their 374 

 offspring three males with slight "nicks" at the tip of 

 their wings, exactly like those of the Pink Beaded male 

 before mentioned, were produced. One of these males 

 was sterile. One of the remaining two was fertile, but 



