266 Messrs. Langley and Very on the 



traction of muscular fibre, the shining tissue being seen through 

 the translucent body-wall. This species of phosphorescence 

 is increased by irritants, but is independent of the presence of 

 oxygen, and is not extinguished or in any way modified by 

 hydrogen or by carbon dioxide. 



Robin and Laboulbene* find the luminous organs of 

 P. noctilucus composed of irregularly polyhedral cells, 

 0*04 to 0*06 millim. thick, between which pass very nume- 

 rous fine trachese and nerves. The inner face of the organ is 

 composed of adipose tissue, and the outer of a transparent 

 modification of the ordinary chitinous covering of the insect. 

 The authors conclude that the light is due to chemical decom- 

 position of a nitrogenous body with formation of crystalline 

 urates. 



Jousset de Bellesme f finds that although the phosphorescent 

 cells, when separated from the body of the insect, continue to 

 glow for several hours, yet if crushed they instantly lose their 

 illuminating power, which indicates that for the production of 

 the light the living cells must retain their integrity, and that 

 they are not mere reservoirs of a phosphorescent substance, 

 but continuous generators of it. He surmises that the light- 

 giving substance may be phosphuretted hydrogen. 



MeldolaX is quoted by Spiller § as having examined the 

 glow-worm spectrum and determined its approximate limits. 



Convoy || finds the glow-worm's light green, and in a small 

 direct-vision spectroscope, showing a continuous spectrum 

 from C to b, appearing like a broad band of green light 

 extending from 0^518 to 0^587, with a faint continuous 

 spectrum into the red to K 656. 



R. DuBois ^[.—Perhaps the most imj^ortant of previous 

 memoirs on phosphorescent insects is by this writer. It con- 

 tains an account of photometric measures in wave-length scale, 

 and also of heat-measures with the thermopile. The latter 

 represent the only attempt even, in this direction, I know of, 

 and seem to be judiciously made, but to be insufficient (on 

 account of the limitations of such apparatus) to establish the 

 author's conclusion that the light is accompanied by no sen- 

 sible heat. This conclusion, we repeat, though very probably 

 correct, does not seem to rest on the evidence of an apparatus 

 of at all the necessary sensitiveness. This memoir, however, 

 appears to be in general an excellent one, and well worthy 

 the student's attention. 



* Comptes Rendus, lxxvii. p. 511 (1873). + Ibid. xc. p. 318 (1880). 



X Proc. Entomol. Soc. p. iii. (1880). § Nature, vol. xxvi. p. 343. 



|| Nature, vol. xxvi. p. 319 (1882). 

 5f Bulletin de la iSociete Zoologique de France, parts 1, 2, and 3, 1886. 



