No. 446.] 



PHO TIN US MA RGINELL L '.V. 



organs and acting as a bellows, and stated thai the photogenic 

 tissue was made up of little spheres, regularly arrangetl and pen- 

 etrated by the tracheae. Leydig and Kolliker in 1S57 definitely 

 recognized the cellular structure of the light-organs. Their work 

 has been followed by that of several other lunopean investigators 

 During the past twenty years Wielowiejski and I '.inery have 

 made important histological researches ui)on species ot i.anip\ris 

 and Luciola. 



All recent workers agree in stating that the ventral ligiit-]ilates 

 of the male lampyrids are composed of two more or less c learly 

 defined layers ; the dorsal, chalky, opaque layer, and the ventral, 

 or truly photogenic layer. The former is comi)osed of fairly 

 regular, polygonal cells, filled with a great quantity of crystals of 

 urate salts. The ventral layer is composed of two distinct ele- 

 ments ; the tracheal structures and intermediate areas of paren- 

 chyma. The parenchyma cells contain fine granules of non-urate 

 composition. The main tracheae of the ])hotogenic segments 

 send vertical branches down through the light-organs. Aside 

 from their profuse branching they show no unusual leatuies 

 until they reach the ventral layer. The tracheal structuies 

 within the ventral layer differ in different forms, and the two 

 species upon which Wielowiejski and p:mery l)ased the bulk ot 

 their work, Lampyris spletididula and Lnciola italua lespei- 

 tively, show a considerable difference in this resi)ect. n 

 Luciola each vertical tracheal axis is surrounded by a eyhndru ai 

 mass of semi-transparent tissue, within which it 

 arborescent manner. The method of branching m "^'^'^'^'^'i'^^^ 

 fasciculate, rather than aborescent, and the tra ' 

 regular in their distribution. Max Schult/e, 

 osmic acid preparations from the light-organs u. /..."./.i-. / -^ -^ 

 didula certain blackened bodies at the i^enpherN ot "^"^ ^ 

 These he found to be penetrated by the finer tiac hca ^^^^^^^^ 

 to find further continuations of the tracheae beyond 

 he called them the " tracheal end cells." W ^'.j^'/their 

 his study of the same species, found that insteax o aN ^^^^^^^ 

 ultimate endings within the so-called - end cells, e .^^^^^^^ 

 branch, sending out fine ''tracheal capillaries^ those of 



beyond the cylinder and in most cases anastomose 



1H64. f<' 



