48 NATURAL HISTORY SOCIETY OF DUBLIN. 



means exclusively, observed in certain of the marine invertebrata, 

 and in the coleopterous order of the insect class. Among the marine 

 Infusoria, the organism named Noctiluca miliaris possesses this property 

 in an eminent degree, most of the orders of the classes Hydroza and 

 Actinozoa, but especially the orders Sertularidae, Physophoridse, Me- 

 dusidse, Lucernaridae, Alcyonaria, and Ctenophora. Many of the 

 Annelids emit light ; the Nereidse are particularly noted for this pro- 

 perty, also species of Syllis, Polynoe, Choetopterus, and Sabella. In 

 the Myriapoda we have the Scolopendra phosphorea, and Geophilus, a 

 genus of luminous centipedes, some of which are by no means scarce 

 in this country ; there are examples of luminosity among the Arachnida, 

 Crustacea, and particularly among the Insecta. Several of the mol- 

 lusca are luminous. The luminosity of living fish is thought by some 

 to be due to an excitement of the phosphorescence of the sea by their 

 rapid motion through the water ; by others it is attributed to the ad- 

 hesion to their bodies of some of the smaller luminous organisms. 

 Pliny* speaks of a fish known as Lucerna, or the lantern fish, because it 

 thrusts from its mouth a tongue that shines like fire, and emits a most 

 brilliant light on calm nights ; but Cuvier considered that the Pyro- 

 soma, one of the Mollusca, is the luminous animal alluded to. Mr. Ben- 

 nett, in a Paper read at the Zoological Society of London, has described 

 some fish of the Scopelus family taken near Cape Horn which emitted 

 vivid phosphorescent light from various parts of the body ; the lumi- 

 nosity entirely disappeared upon the death of the fish. As we rise in 

 the scale of creation instances become rarer of vital luminosity under 

 ordinary conditions, and we are obliged to end with a mere reference to 

 the statement of Azara that the urine of the Skunk is habitually lu- 

 minous. 



The presence of the Noctiluca miliaris is one of the causes of the 

 phosphorescence of the sea — a phenomenon which is observed, though 

 a less splendid degree, in cold and temperate latitudes as well as within 

 the tropics. This organism, from the simplicity of its structure, is 

 classed among the Protozoa, yet its light-producing power ranks among 

 one of the most subtle problems of nature. M. Suriray, a doctor of 

 medicine, while investigating lhe cause of the phosphorescence of the 

 sea water at Havre, appears to have been the first who observed, 

 and called attention to, the genus Noctiluca, which he described 

 and figured in the Memoir which he communicated to the class of 

 Sciences of the French Institute. In size the Noctiluca miliaris 

 varies from *04 to '01 of an inch; so that a single drop of sea water 

 may contain one or several individuals, and when they are nume- 

 rous the water may assume the appearances of a phosphorescent solu- 

 tion. By filtering this phosphoric water, these organisms can be ar- 

 rested and retained for examination ; the water which has passed through 

 the filter has lost its luminous property, which can be restored to it at 



Hist. Nat.," lib. ix., c. 43. 



