Vol. XXviii] ENTOMOLOGICAL NEWS. 309 



The narrow hypodermal ligaments which are continuous 

 with the hypodermis and the photogenic organ, often appear 

 longitudinally striated, due probably to a slight modification of 

 the hypodermis in those regions. In a sagittal section these 

 attachments are continuous longitudinally with the reflective 

 layer, the region between these attachments next to the hypo- 

 dermis being occupied entirely by the luminous cells. Since 

 the reflective layer lies like a cap over the inner portion of 

 the photogenic organ, its cells cover all of the organ except 

 that portion next to the hypodermis. 



At the meeting of the American Society of Zoologists, at 

 New York, in December, 1916, Dahlgren reported observa- 

 tions which he had made on the development of the adult or- 

 gans in the pupa of Photicris pennsylvanica. He found that 

 the larval organs degenerated, and that new ones were formed, 

 in different body segments, by the proliferation of hypodermal 

 cells. Williams in his work on the development of the light 

 organs in the pupa concludes that they are derived from 

 fat cells. However he states : "The photogenic organ, when 

 in the process of formation, frequently suggests a hypodermal 

 origin, for it is then rather structureless and closely applied 

 to the body wall. Indeed some sections show the hypodermis 

 sending up extensions between the cells of the organ." My 

 observations on the pupal development of the photogenic 

 organ, though essentially the same as quoted from Williams' 

 paper, have led me to conclude, as Dahlgren, that the adult 

 organs in the pupa arise from hypodermis. 



Wheeler and Williams (1915) in their study of a my- 

 cetophilid fly of the New Zealand caves, find that the light 

 organs are a modified portion of the Malpighian tubules. 

 These structures, as is well known, are of ectodermal origin, 

 and this furnishes a clear instance of light organs from the 

 ectoderm in insects. 



All the evidence which I have obtained from the studies 

 above outlined, strengthen my belief that Vogel and Will- 

 iams were mistaken in their interpretations of the early light 

 organ, and that, instead of arising from fat cells, the em- 



