ADTHORiS ABSTRACT OF THIS PAPER ISSUED 

 BT THE BIBLIOGRAPHIC SERVICE, FEBRUARY 2 



A CHANGE IN THE BAR GENE OF DROSOPHILA 



MELANOGASTER INVOLVING FURTHER 



DECREASE IN FACET NUMBER AND 



INCREASE IN DOMINANCE^ 



CHARLES ZELENY 



University of Illinois 



NINE FIGURES 



CONTENTS 



Introduction 293 



Temperature control 294 



Origin, behavior, and location of bar eye 297 



Origin of ultra-bar 300 



Constancy of ulti'a-bar 304 



The change in dominance 308 



The location of the ultra-bar gene 311 



Conclusions 321 



Summary 323 



INTRODUCTION 



In connection with a study of the germinal and environmental 

 factors affecting eye-facet number in Drosophila melanogaster, 

 which is in progress in the Zoological Laboratory at the Uni- 

 versity of Illinois, several interesting germinal changes have been 

 observed. Some of these involve accessory factors while others 

 are changes in the bar gene itself. Among the latter is the re- 

 verse mutation to full eye first described by H. G. May ('17) and 

 since then observed several times by the writer. The change to 

 be described is equally interesting. It appeared in the second 

 low selection for facet number in white bar and involves -further 

 decrease in facet number. Like reverse mutation, it is due to a 

 change in the bar gene itself, and not to the appearance of an 

 accessory factor; it is in the same direction as the original bar 



^ Contributions from the Zoological Laboratory of the University of Illinois, 

 no. 149. 



293 



