634 



ANNUAL REGISTER, 1810. 



animal, it shone brilliantly like the 

 fire-fly. 



In the month of June in the 

 same year, he picked up another 

 luminous insect on a sandy beach, 

 which was also covered with a thin 

 shell; but it was of a different 

 shape, and a larger size than the 

 animal taken in the Arabian sea. 



By comparing the above de- 

 scription with an elegant pen-and- 

 ink drawinj;, which was made by 

 Captain Horsburgh, and accom- 

 panied his paper, I have no doubt 

 that both these insects were mo- 

 noculi ; the first evidently belongs 

 to the genus limulus of MuUer ; I 

 shall therefore beg leave to dis- 

 tinguish it by the name of limulus 

 noctilucus. 



My pursuits, and the state of 

 my health, having frequently led 

 me to the coast, 1 have had many 

 opportunities of making observa- 

 tions upon the animals which illu- 

 minate our own seas. Of these I 

 have discovered three species; one 

 of which is a beroe not hitherto 

 described by authors; another 

 agrees so nearly with the medusa 

 hemispherica, that I conceive it to 

 be the same, or at icast a variety 

 of that species; the third is a mi- 

 nute species of medusa, which I 

 believe to be the luminous animal 

 so frequently seen by navigators, 

 although it has never been dis- 

 tinctly examined or described. 



I first met with these animals 

 in the month of October 1804-, at 

 HerneBay,a small watering-place 

 upon the northern coast of Kent. 

 Having observed the sea to be 

 extremely luminous for several 

 nights, I had a considerable quan- 

 tity of the water taken up. When 

 perfectly at rest, no light was 

 emitted, but on the slightest agi- 



tation of the vessel in which the 

 water was contained, a brilliant 

 scintillation was perceived, parti- 

 cularly towards the surface; and 

 when the vessel was suddenly 

 struck, a flash of light issued from 

 the top of the water, in conse- 

 quence of so many points shining 

 at the same moment. When any 

 of these sparkling points were re- 

 moved from the water, they no 

 longer yielded any light. They 

 were so transparent, that in the 

 air they appeared like globules of 

 water. Tiiey were more minute 

 than the head of the smallest pin. 

 Upon the slightest touch, they 

 broke and vanished from the 

 sight. Having strained a quantity 

 of the luminous water, a great 

 number of these transparent cor- 

 puscles were obtained upon the 

 cloth, and the water which had 

 been strained did not afterwards 

 exhibit the least light. I then 

 put some sea water that had 

 been rendered particularly clear, 

 by repeated filtrations, into a 

 large glass, and having floated in 

 it a fine cloth, on which I had 

 previously collected a number of 

 luminous points, several of thera 

 were liberated, and became dis- 

 tinctly visible in their natural 

 element, by placing the glass 

 before a piece of dark-coloured 

 paper. They were observed to 

 have a tendency to come to the 

 surface of the water, and after the 

 glass was set by for some time, 

 they were found congregated to- 

 gether, and when thus collected in 

 a body, they had a dusky-straw 

 colour, although individually they 

 were so transparent as to be per- 

 fectly invisible, except under par- 

 ticular circumstances. Their sub- 

 stance was indeed so extremely 



