PHOTOGENIC ORGANS OF LAMPYRIDS 147 



Dubois ('98), in his studies on the light-organs of Lampyridae 

 and of Pyrophorus noctiluca, found, from an examination of the 

 ova of the Lampyrids, a resemblance between the blastoderm 

 cells and the photogenic cells of the larva, pupa and adult. He 

 concludes with reason that it is these cells and not the nutritive 

 yolk which give rise to the light-organ. It would seem that 

 some of the photogenic material is transmitted to the eggs by 

 the mother insect. He says, p. 310: 



Les noyaux se sont multiplies dans un certain nombre de gros plas- 

 tides hypodermiques, et de ceux-ci s'echappent des files de jeunes ele- 

 ments, dont la masse forms l'organe lumineux larvaire . . . ; 

 plus tarde, celui-ci s'isolera: la photographie de cette nouvelle coupe, 

 que je projette sur le tableau, vous permet de comprendre facilement 

 sa texture. 



As a result of this proliferation, the underlying hypodermis is 

 very sparse or lacking. His figure 139 illustrates this condition. 

 Dubois' figure of the photogenic organ of Pyrophorus noctiluca 

 is rather different from that of the Lampyridae. Dahlgren and 

 Kepner ('08), and Geipel ('15) figure a portion of the photogenic 

 organ of Pyrophorus, and it can be seen that it has essentially 

 the same structure as that of Photuris and Photinus. Dubois 

 describes, further, the formation of the fight-organ in the female 

 Lampyris noctiluca, and bases his observations largely upon a 

 pupa about to transform into an adult. The process is described 

 as essentially similar to that which occurs in the larva, the 

 photogenic cells being derived from the underlying hypodermis 

 in such a manner that the oldest of the light cells are nearest the 

 alimentary tract. My studies on Photinus consanguineus show 

 that the reverse is true, for the older cells (as far as position is 

 concerned) are nearest the hypodermis, although from a develop- 

 mental standpoint they are all of about equal age. Marchal 

 ('11) follows Dubois and regards the photogenic tissue as ecto- 

 dermal. 



Treviranus ('18) seems to be among the first investigators to 

 have decided that the fat-body and light-organ are of the same 

 substance, since he says, p. 102: "Ich finde die leuchtende Sub- 

 stanz dieser Kafer (Elater noctilucus und phosphoreus) ganz 



