HEREDITY OF BODY COLOR IN DROSOPHILA 



T. H. MORGAN 



From the Zoological Laboratory, Columbia University 



FOUR COLORED FIGURES PLATE 1 



Cultures of the fruit fly, Drosophila ampelophila, have given 

 rise to three mutations in the color of the body and wings. The 

 origin of these new types has beeA briefly described in a pre- 

 liminary note, and some of the main facts connected with their 

 inheritance have been given there, but the principal data on 

 which the statements rest have been reserved until the present 

 time. The results include 81,070 counts. It may be asked 

 what advantage is there in doing the experiments on so large 

 a scale. Why would not a few cases with suitable tests show 

 the mode of inheritance of the factors involved? The answer 

 is two-fold. The question of the relative viability can only 

 be determined in this way, and for further work with these body 

 colors it is necessary to know what role this condition plays in 

 the numerical results. In the second place it seemed worth 

 while to illustrate on a large scale the phenomenon of sex-linked 

 inheritance. It is an impressive fact, for instance, to find in 

 the F2 generation (out of black female by brown male) 6124 

 black females, 3015 black males and 2472 brown males. Not 

 a single brown female in 11,000 grandchildren. While in the 

 reciprocal cross there are present 2191 black females, 1987 black 

 males, 1532 brown females and 1448 brown males. Such results 

 cannot fail, I think, to impress those who take a sceptical atti- 

 tude toward the modern study of heredity. 



The black and the yellow mutants arose directly and inde- 

 pendently from inbred, normally colored, or gray flies. The 

 brown flies were produced by crossing and extracting. They 

 also arose independently in cultures related to the black flies 



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