UNIVERSITY OF CALIFORNIA PUBLICATIONS 



IN 



ZOOLOGY 



Vol. 13, No. 13, pp. 495-515, 1 figure in text December 9, 1916 



THE INHERITANCE OF EXTRA BRISTLES IN 

 DROSOPHILA MELANOGASTEB MEIG. 



BY 



EDNA M. BEEVES 



The object of this paper is to show the inheritance of extra bristles 

 in Drosophila melanogaster Meig. {=D. ampelophila Leow), and to 

 see if selection had any influence on the results. Similar work on 

 this subject has been done by Edwin Carleton MacDowell (1915). 

 The results obtained in my work agree in part and disagree in part 

 with his conclusions. 



So many experiments have been made of late with this little fly, 

 Drosophila, by Morgan and his students, that it is familiar to all 

 zoological workers. The character used in this case was the number 

 of bristles, its inheritance and variation. The bristles, normally four 

 in number, appear on the dorsal surface of the thorax and form a 

 regular rectangular pattern, thus : : : The flies used originally came 

 from Professor Morgan's stock in New York, but have been bred in 

 the laboratory of genetics at Berkeley for two years. 



In a mass culture of 235 flies, five, or 2.97 per cent, were found 

 with one extra bristle. Three of these were females and two were 

 males. All of these were mated with normals and an account kept 

 of the subsequent generations. After the first mating, three kinds 

 of crosses were made: (1) normal X normal, (2) normal X extra, (3) 

 extra X extra. 



The bottles and food were sterilized to prevent any infection. The 

 bottles were labelled and the hatchings were immediately removed 

 from the bottles to prevent any overlapping of generations. The 



