'212 Zoological Society, 



scintillations he considers are probably influenced, in some measure, 

 by an electric condition of the atmosphere, as at those particular 

 times they were observed to be much more vivid and incessant than 

 at others. The other kind of luminosity spoken of has more the 

 appearance of sheets or trains of whitish or greenish light, often suf- 

 ficiently brilliant to illuminate the vessel as it passes through, being 

 produced by various species of Salpa, Bero'e, and other Molluscs, 

 while in the former case the scintillations, which adhere in myriads 

 to the towing net when drawn out of the water, probably originate 

 in animalcules so minute that the only indication of their presence 

 is the light which they emit. 



The author remarks that " the luminosity of the ocean is often 

 seen with greater constancy and brilliancy of effect between the la- 

 titudes 3° and 4° north and 3° or 4° south of the equator, than at 

 any other part of the tropical regions. This circumstance, which I 

 have observed myself, if found to be borne out by repeated obser- 

 vations, may be occasioned by the eddies arising from currents, for 

 it is a curious fact worth noticing, that where currents are known to 

 exist, the luminosity of the ocean has been observed to assume a 

 higher degree of brilliancy. Now the westerly current is supposed 

 to run between those parallels of latitudes from 20° or 22° west lon- 

 gitudes towards the Brazilian coast perpetually, and it is not im- 

 probable that nearly at the termination of the north-east trade wind 

 a current joins with a similar current carried by the south-east trade 

 wind ; both uniting in forming the westerly current may thus cause 

 a greater assemblage of the various tropical molluscs and crustaceous 

 animals, a number of which possessing luminous properties may im- 

 part by their presence a higher degree of phosphorescence in that 

 particular portion of the ocean than is observed in other situations 

 except from similar causes. That the diffusion of the phosphoric 

 light possessed by these molluscs does not solely depend on the 

 creatures being disturbed (such as the passage of the ship through 

 the water, or other somewhat similar causes,) is evident, as a lumi- 

 nous mass may frequently be observed to gradually diffuse its bril- 

 liant light, at some distance from the ship, without any apparent 

 disturbance ; and often during calm nights a similar glow of light is 

 diffused over the water, without there being any collision of the waves 

 to bring it forth ; and if a light breeze springs up during the same 

 night, the passage of the vessel leaves no brilliant trace in its wake, 

 although the same spontaneous diffusion of light is observed in the 

 water at some distance to be repeated as before ; the phosphoric 

 light being confined apparently solely to the occasional groups of 

 molluscs, which when we succeeded in capturing them in the towing 

 net, resembled for the most part pieces of crystal cut into various 

 fantastic forms, round, oval, hexagonal, heptagonal, &c. From the 

 bodies of these a faint or a bright light (according to the greater or 

 less duration of time the animal may have been removed from the 

 water, that is, we may say, by the intensity of its light we can 

 judge of its healthy or vigorous state,) would be seen to issue in mi- 

 nute doti.; Ircin various parts; and on the examination of both large 



