No. 446.] PHO TIN US MA RGINELL US. 1 4 1 



that in Luciola the tracheoles in all cases end free. This is 

 shown in his figures 4 and 7, Plate XIX. 



In Lampyris Wielowiejski figures the tracheoles as winding 

 irregularly and twisted and looped about each other. In Pho- 

 tinus they are generally almost straight. They may be slightly 

 wound about each other, but for the most part they pass directly 

 from one cyUnder to another. 



Both Wielowiejski and Emery agree in considering that the 

 tracheoles pass between the cells of the parenchyma, although 

 positive proof is difficult. In no case has any portion of a 

 tracheole been found within the parenchyma cells, although they 

 have been seen closely applied to the exterior of the cells. In 

 surface sections of Photinus the areas between the tracheoles 

 would appear to correspond to cells, each possessing a nucleus. 

 It thus seems altogether probable that in their course outside 

 the cylinders the tracheoles are intercellular. 



In 1864 Max Schultze studied the light organs of Lampyns 

 splendidula, using osmic acid as a fixer. He found the finer 

 tracheal branches losing their spiral thickening and passmg mto 

 star-shaped, finely granular bodies which he believed to be true 

 cells possessing distinct nuclei and cell membranes. He failed 

 to find any continuation of the trachea beyond these stellate 

 cells, and so assumed that these cells enclosed the ultimate 

 endings of the trachea. The name "tracheal end-cells, as 

 given by Max Schultze has since been generally used, even by 

 those who knew it to be a misnomer. 



In his studies of the same species, Wielowiejski found he 

 trachea passing into the stellate ''end-cells" of Max bctiuitze, 

 but instead of ending there, branching to form tracheoles ^v hit 1 

 penetrate the inter-cylindrical parenchyma. He be icvecl _icsc 

 "end-cells " to be true cells, much flattened and simi ar in ori 

 to the endothelial cells of vertebrates. They extend about c 

 bases of the tracheoles in a web-like manner and are more or ess 

 stellate in shape. These cells show a characteristic reaction 

 with osmic acid, causing a precipitate to be formed, espec ^ > 

 about the point of origin of the tracheoles. The tracheal wig 

 appears constricted at its apex, and is intensely blackened by 

 the osmic acid. The effect of the acid varies, in some cas 

 entire end cell being uniformly blackened. 



