040 



ANNUAL REGISTER, 1810. 



Mayer conjectured that the sur- 

 face of the sea imbibed hght, 

 which it afterwards discharged. 

 Bajon and Gentil thought the light 

 of the sea was electric, because it 

 was excited by friction. Forster 

 conceived that it was sometimes 

 electric, sometimes caused from 

 putrefaction, and at others by the 

 presence of living animals. Fou- 

 geroux de Bondaroy believed that 

 it came sometimes from electric 

 fires, but more frequently from 

 the putrefaction of marine animals 

 and plants. 



I shall not trespass on the time 

 of the Society to refute the above 

 speculations : their authors have 

 left them unsupported by either 

 arguments or experiments, and 

 they are inconsistent with all as- 

 certained facts upon the subject. 



The remarkable property of 

 emitting light during life is only 

 met with amongst animals of the 

 four last classes of modern na- 

 turalists, viz. mollusca, insects, 

 worms, and zoophytes. 



The mollusca and worms con- 

 tain each but a single luminous 

 species ; the pholas dactylus in 

 the one, and the nereis noctiluca 

 in the other. 



Some species yield light in the 

 eight following genera of insects: 

 elater, lampyris, fulgora, pausus, 

 scolopendra, cancer, lynceus, and 

 limulus. The luminous species of 

 the generalampyris and fulgora are 

 more numerous than is generally 

 supposed if we may judge from 

 the appearance of luminous organs 

 to be seen in dried specimens. 



Among zoophytes we find, that 

 the genera medusa, beroe, and 

 pennatula, contain species which 

 afford light. 



The only animals which appear 

 to possess a dictinct organization 

 for the production of light, are 

 the luminous species of lampyris, 

 elater, fulgora, and pausus. 



The light of the lampyrides is 

 known to proceed from some of 

 the last rings of the abdomen, 

 which, when not illuminated, are 

 of a pale yellow colour. Upon 

 the internal surface of these rings 

 there is spread a layer of a pecu- 

 liar soft yellow substance, which 

 has been compared to paste ; but 

 by examination with a lenslfound 

 it to be organized like the com- 

 mon interstitial substance of the 

 insect's body, except that it is of 

 a closer texture, and a paler yel- 

 low colour. This substance does 

 not entirely cover the inner sur- 

 face of the rings, being more or less 

 deficient along their edges, where 

 it presents an irregular waving 

 outline. I have observed in the 

 glow-worm, that it is absorbed, 

 and its place supplied by a com- 

 mon interstitial substance, after 

 the season for giving light is past. 



The segments of the abdomen, 

 behind which this peculiar sub- 

 stance is situated, are thin and 

 transparent, in order to expose the 

 internal illumination. 



The number of luminous rings 

 varies in different species of lam- 

 pyris, and as it would seem at dif- 

 ferent periods in the same indivi- 

 dual. 



Besides the luminous substance, 

 above described, I have discovered 

 in the common glow-worm, on 

 the inner side of the last abdomi- 

 nal ring, two bodies, which to the 

 naked eye appear more minute 

 than the head of the smallest pin. 

 They are lodged in two slight de- 



