100 POPULAR ILLUSTRATIONS OF 



seen darting about as if in consternation. The light was sufficient 

 to enable me to see the most minute object on deck. On drawing 

 up a bucketful of water and stirring it with the hand it presented 

 one mass of light, not in sparkles as usual, but in actual coruscations." 

 Trans, of Literary and Historic Society of Quebec. 



The animals chiefly concerned in marine luminosity are those 

 we have already dealt with. The most common, perhaps, of all 

 is a small animalcule which occurs in countless myriads in 

 the sea viz., the Noctiluca miliaris. This curious creature is 

 one of the Amoebae. After the Noctiluca the Ccelenterata supply 

 the greatest number of light-giving creatures. When individual 

 objects are discerned the phosphorescence is caused generally 

 by one or other of the covered-eyed Medusae or Pelagia, and the 

 scintillations so often noticed are produced principally by one of 

 the small . naked-eyed species viz., Thaumantias lucifera, a beau- 

 tiful creature about the size of a split pea, having round the rim 

 of the umbrella no less than eighty-four tentacles. As to the 

 cause of phosphorescence a great deal has been surmised. All 

 modern scientific observers agree in the fact that it is produced by 

 animal motion ; that it is therefore a vital act, and not a consequence 

 either of slow combustion or the production of a phosphorescent 

 body or mucus. The light is clearly electrical. Kolliker believes 

 that the luminous organs are a nervous apparatus similar to the 

 electrical organs of fishes ; but this presupposes the existence of a 

 nervous eystem in animals where it has not been discovered by the 

 strictest examination. The one great and prominent function of the 

 sarcode of the Amoebae is, as we have seen, that of motion ; and 

 this sarcode is differentiated in the higher animals into muscular 

 tissue. It is not, therefore, very difficult to understand how such 

 motion may be accompanied by electrical discharges, and thus 

 constitute the phenomenon known as phosphorescence. 



In the Medusae it is probable that the light is more or less con- 

 nected with the discharge of those curious thread cells of which I have 

 said so much. Forbes remarks that he never saw phosphorescence 

 in the naked-eyed Medusae spring from any part of the body except 

 the tentacles, and all writers refer to the lithocysts as more or less 

 connected with the phenomenon. Now, as we have seen, these parts 

 of the bodies of Medusae are the principal seat of the thread cells, 

 and the inference I have drawn is, I think, supported by the fact 

 that a Medusa, when fresh caught, will emit light when irritated, 

 but that by a repetition of the process the power soon ceases, 

 which would naturally be the case when all the thread cells were 

 discharged. Forbes, however, says that none of the naked-eyed 

 Medusae have the power of stinging. But it must not be inferred 



