No. 446.] PHOriNUS MARGINELLUS. 



129 



The material was all stained after the sections were cut. The 

 Gilson and alcoholic sections were stained for about two minutes 

 in Gage's chloral hematoxylin, and for a half minute in eosin. 

 This gave satisfactory general results. A double stain with 

 alum carmine and picric acid did not prove a good stain after 

 Gilson's fluid. Following fixation with osmic acid, Hermann's 

 or Flemming's fluids, safranin proved most satisfactory. The 

 sections were stained for twenty-four hours in a mixture of equal 

 parts of saturated aqueous and alcoholic solutions of safranin, 

 then differentiated in absolute or even slightly acid alcohol. 

 Iron hematoxylin is also a good stain for osmic acid material. 



Carbol-xylene was used as a clearer, and the sections were 

 mounted in Canada balsam. 



Teazed preparations were made by dissecting out the light- 

 organs entire, placing them for from fifteen to thirty minutes in 

 • 5% osmic acid, then for a few minutes in weak caustic potash, 

 and teazing in normal salt solution. 



Experiments with methylene blue injection were not successful. 

 Only one insect showed any coloration of the central ner\'ous 

 system, and in that the finer nerves could not be traced. It is 

 difficult to get a good injection with such small insects. How- 

 ever, my attempts in this line were begun near the close of the 

 collecting season, and with further experimenting it is possible 

 the results might have been better. The most successful sjicc i- 

 men was killed an hour and a half after injccti(;n. 



Since the old idea that the firefly's light was dependent upon 

 the presence of phosphorus or some simikir sul)staiuv has been 

 abandoned, other theories have been advaiKed 111 attempt to 

 explain the phenomenon. The view generally ac( eptcd is that 

 the light results from the oxidation of a substaiuc jnochu cd by 

 the metabolism of the light-organ cells. i he nature of this 

 substance has not been determined, but that its ])hot(),i;ciiK |)ru[)- 

 erty is independent of the life of the cell is {)r()\ e(l by thr fact 

 that when the organs are dried and reduced to a powder the 

 light reappears under the influence of air and moisture. \\ hen 

 the fresh photogenic tissue is crushed, the light increases in 

 brilliancy, and it is some time before it wholl\ disap|)ears. 

 Radziszewski ('80) through his study of the artificial luminosity 



