Roi/al Societi/. 275 



Fire-fly is of a pale yellowish tint, with continual flashes of 

 vivid light: its variations are not connected with the motions of 

 the insect's wings, nor are they produced, as some have affirmed, 

 by the frequent intervention of a membrane. This animal may 

 be seen shining in full moon-light ; which is not the case with 

 its congeners. The luminous power of these Insects resides in 

 an adhesive, transparent, granulated substance, deeply pene- 

 trated, according to Macaire, with nervous filaments. This sub- 

 stance continues to shine, when amputated, for a space of time 

 never exceeding twenty minutes, and that in any medium ; as 

 under mercury, in water, in various gases ; and in vacuo. When 

 the life of the animal and the ordinary luminous power have 

 both been destroyed by strong poisons, as tincture of Nux vo- 

 mica, &c. a fixed light appears, which continues for twelve or 

 fourteen hours. Irritants excite the luminous power in all cases, 

 and disorganizing substances destroy it. Dr. Todd concludes 

 that this power is solely an effect of vitality, and that the light 

 may be considered as animal light; being analogous to animal 

 heat, which, he observes, arises from a power of separating heat 

 from its combinations with matter. He adopts the hypothesis that 

 its principal use is that of guiding the male insects to the female, 

 in the season of sexual congress : the males always approach any 

 light ] and sometimes even the shining females of other spe- 

 cies, until they come very near them. The fact that the larvae 

 and even the ova possess a degree of the luminous faculty. Dr. 

 Todd does not consider as militating against this explanation ; for 

 various organs are partially developed in the earlier stages of 

 many animals, which are only to be used by them when arrived 

 at their perfect state. 



Maj/ 6. — The reading was commenced of a paper On Univalves ; 

 by Charles Collieu, Esq. Staff Surgeon ; communicated by Sir 

 James Mac Gregor, Bart. F.R.S. 



Mai/ 13. — Major Charles Hamilton Smith, of Guernsey, A.L.S. 

 author of several Zoological papers in the Linnean Transactions, 

 was elected a Fellow of the Society; and the reading of Mr. 

 Collier's paper was concluded. 



Mr. Collier commences this paper, by stating that he had once 



