AUTHOR 8 ABSTRACT OF THIS PAPER ISSUED 

 BY THE BIBLIOGRAPHIC SERVICE, FEBRUARY 20 



ORIGIN AND DEVELOPMENT OF THE LIGHT-ORGANS 

 OF PHOTURUS PENNSYLVANICA DE GEER 



WALTER N. HESS 



Department of Entomology, Cornell University 



FIVE PLATES (SEVENTEEN FIGURES) 



CONTENTS 



Introduction 245 



Materials and methods 246 



History of embryological work on the light-organs of insects 247 



Location and structure of the light-organs 250 



Origin and development of the larval light-organs 251 



Origin and development of the adult light-organs 254 



Phagocytosis of the larval light-organs 262 



Summary 263 



Bibliography 265 



INTRODUCTION 



In spite of the fact that the Ught-organs of fireflies have been 

 the object of much study during the past century, comparatively 

 httle has been done on their development. During the past 

 few years, however, this phase of the subject has received more 

 attention, though as yet the question of their origin is not 

 settled. 



Shortly after the publication of the two brief conflicting 

 reports, regarding the origin and development of the Hght- 

 organs in insects, by Vogel ('13) and Dubois ('13), the author 

 undertook a study of the development of these organs. Dur- 

 ing the winter of 1916 to 1917 there appeared two more articles 

 on the origin of these organs (Williams, '16, and Dahlgren, 

 '17), but as these contradicted one another, the question was 

 considered still unsettled. At that time the present study, 

 which had been largely devoted to the development of the 

 hght-organs in the embryo, was interrupted by the war, so a 

 brief preliminary report was published. Upon resuming this 



245 



