141 



last, or anal segment. In water of the temperature 

 ofllOF., it crawled about apparently disconcerted, 

 emitting two gleams, which were as suddenly 

 quenched ; but on being withdrawn, did not seem 

 inconvenienced. The insect died at a temperature 

 of 125 F. ; but being suffered to remain in water 

 at 116F., light was educed, became extinct in 90 

 seconds, and could not be rekindled by a temperature 

 of 156. The maximum of brilliancy obtains at a 

 temperature of 99, and is less intense and less per- 

 manent at temperatures superior to this grade; while 

 it may be inferred, that the temperature at which the 

 animal dies is also that at which the luminous matter 

 becomes particularly faint and evanescent. 



When we plunged the luminous spherule in naphtha, 

 it was apparently immediately extinguished ; but this 

 seemed to be in consequence of the opacity of the 

 fluid, for when withdrawn it shone with undiminished 

 brightness. In solution of nitrate of silver, it shone 

 for some minutes with undecreasing light ; in ethereal 

 solution of gold, the luminous matter ceased to shine 

 in 65 seconds perhaps from a deposition of a film 

 of gold on the luminous spherule ; in concentrated 

 chromic acid, it remained luminous for several minutes 

 the acid being opaque, the duration was determined 

 by withdrawing the luminous matter from the liquid. 

 When we pressed the luminous matter into a flat disc, 

 the light appeared momentarily, as so many minute 

 scattered points, which became promptly evanescent 

 from the rupture of the capsule including it. Two 

 spherulae, with a portion of the interstitial matter, 

 were detached from a glow-worm : on being with- 

 drawn, they emitted light, but by a contractile power, 

 soon became imbedded amid this substance, from 

 which they could, however, be easily expressed, and 



