408 



Dr. J. H. Pring's Observations and 



objects on my table, pictures hanging against the wall, &c. ; 

 the luminous effect, however, being very transitory, and only 

 at the moment of agitation. 



Viewed the following morning by daylight, innumerable 

 very minute gelatinous bodies, of a globular form, could be 

 perceived even with the naked eye, floating near the surface 

 of the water; and on gently shaking the bottle containing 

 them, they could be observed to descend to a short depth, 

 gradually, however, rising again to their former level when 

 left at rest. From repeated observation of this fact, it would 

 appear that these little animals are naturally, or otherwise 

 possess the power of rendering themselves, specifically lighter 

 than sea water ; and this property appears to be a living attri- 

 bute, since it ceases, and they are seen immediately to sink to 

 the bottom of the vessel, upon the occurrence of death. 



Placed under the field of a microscope, and magnified to 

 about the size of a large pea, the Noctiluca presented the ap- 

 pearance of a highly delicate and translucent membranous 

 sac, of almost spherical form, and having the look on one side 

 as if the mouth of the sac had been puckered up and turned 

 inwards; yet this puckered part does not take an exactly cir- 

 cular form corresponding to a description which has been 

 given of it, as "producing such an appearance as would arise 

 from tying the neck of a round bag and turning it into the 

 water;" but extends rather in a longitudinal direction, giving 

 somewhat the effect of a longitudinal cleft ; and fi"om one end 

 of this cleft is observed to protrude a lengthened filamentous 

 body, which seems to be a sort of tentaculum, and during the 

 life of the animal is seen to be in almost constant motion. 



I have endeavoured in vain to 

 obtain a more accurate view of 

 this appendage; but the state of 

 constant motion it is in, together 

 with the extreme minuteness and 

 delicacy of the whole animal, have 

 hitherto rendered my efforts un- 

 availing. That it is occasionally 

 employed as an organ of locomo- 

 tion there can be no question, and 

 some of the movements executed 

 by it have appeared to me very 

 surprising. Thus 1 have wit- 

 nessed it extended above the 

 animal, and then used as a fulcrum, 

 as it were, to draw the body of the 

 animal upwards towards itself; yet 



Magnified view of the Noctiluca 

 miliaria. Natural size, iTrWh part 

 of an inch in diameter. 



