402 



EAMBLES OF A NATUEALIST-. [Oh. XXIII. 



varies probably according to the depth of the animal pro- 

 ducing it below the surface, — sometimes it is of considerable 

 brilliancy, and sometimes so pale that it would not have been 

 noticed but for its suddenness. The colour is always whitish, 

 and the form of the flash round, brightest in the middle, and 

 becoming indistinct at the circumference. I have on some 

 occasions seen these flashes occur in such numbers and with 

 such rapidity that it would have been impossible to count 

 them; though, more commonly, they were comparatively 

 few and far between. 



But that which interested me most in these flashes of 

 light was the fact that they always occurred at a distance 

 from the path of the ship. Although I have seen them 

 accompanyiag the moonshaped patches of light in the ship's 

 wake, the places from which I could best observe the flashes 

 were the forecastle or the gangways, when they could be 

 seen in the smooth water several yards distant from the 

 ship's side, and entirely uninterfered with by the ship's 

 motion. This fact proved to me that there were spontaneous 

 emissions of light by some animals deep below the surface, 

 which voluntarily, and at intervals, gave out a bright corusca- 

 tion. Moreover, although rarely, on following with the eye 

 the spot where the flash appeared, it could be sometimes 

 seen to re-appear further astern, as though the emission was 

 recurrent at definite intervals, as has already been described 

 in the case of the luminous beetles called fireflies at Singa- 

 pore. I have also noticed on one occasion that the flash, 

 instead of instantly disappearing, was followed by a faint 

 glow, which vanished gradually; but whether this was an 

 optical illusion of the retina or not I cannot be sure, though 

 I believe not. 



Whatever may be the animals which produce these lumin- 



