20 M. de Quatrefages on the Phosphorescence of 



II. On the mode of j)roducing light by Manne Invertebrata. 



Almost all researches undertaken to discover the manner of 

 producing light in animals, have been made on insects, especially 

 the Lampyri and Elatcvs. Spallaiizani, Burmeister, but above 

 all, Macaire*, have published results apparently decisive. These 

 experiments undertaken and varied by JNIatteuccif, with all the 

 precautions furnished by experimental science at the present day, 

 leave, we think, no room for doubt. In the insect which he ex- 

 amined, the light was produced by an actual slow combustion 

 analogous to that of phosphorus exposed to the air. This light 

 is extinguished in a vacuum and in the irrespirable gases ; it re- 

 appears by contact with atmospheric air; it is sensibly brightened 

 in pure oxygen ; it continues in animals after they are dead, or 

 even cut to pieces. The particular substance from which it ema- 

 nates may be isolated, and may leave upon the fingers or the 

 dissecting instrument a luminous streak which disappears only 

 on drying; a little dampness even, in certain cases, is sufficient 

 to restore the phosphorescence; finally, the production of this 

 light is accompanied in the living animal, as well as in its dead 

 carcass, by the escape of carbonic acid. Everything concurs then 

 to show that the phosphorescence of insects, and probably of all 

 aerial animals, is owing to a peculiar secretion, whose substance 

 combining slowly with oxygen produces light. 



But can this explanation of phosphorescence be applied to in- 

 vertebrated animals living in water ? Such questions imme- 

 diately arise, but yet have been overlooked by most naturalists. 

 The greater part of the observers from whose works we have 

 cited have been satisfied with knowing that animals produced 

 the phosphorescence of the sea ; some have gone a little farther 

 and have attributed this phsenomenon to the secretion of a lumi- 

 nous liquid. This opinion appears generally adopted, and traces 

 of it may be seen even in the writings of some naturalists who 

 have not formally stated it. The experiments of Spallanzani 

 and the observations of many travellers seem fully to confirm 

 this view, which is evidently correct in souie cases. Duges, for 

 instance, has decidedly adopted it, and has implied a resemblance 

 between the phosphorescence of the Medusae and Annelids, &c., 

 and that of the Elaters and Lampyrides J. 



A very different opinion has been set forth by M. Gilbert, an 

 officer of the corps of naval engineers, who, without being aware 

 of the investigations of others on this subject, had seen the Noc- 

 iiluca, and describes them rather coarsely, but in a manner easily 



* Journal de Phj^sique, t. xciii. 



t Lec;on sur les jihenomenes physiques des corps vivants, 8'' legon. 



X Traite de Physiologic comparee, t, ii. Montpellier, 1838, 



