376 THE OCEAN. 



to be very full of small slimy particles without any 

 definite form, which gave out light when the water 

 was stirred. These were probably Medusae, torn but 

 yet living, as in some cases fragments of these ani- 

 mals are very tenacious of life. Several minute Me- 

 dusae, of various species gave out light, which seemed 

 to be more vivid on any extraordinary excitement of 

 the animals. A drop of sulphuric acid being put 

 into a glass of water, several bright flashes of light 

 were seen. One of the little animals was taken up in 

 a drop of water on the point of a pen ; on a drop of 

 acid being added, it gave out a momentary spark and 

 instantly died. Several new species of luminous 

 animals were discovered by thus mingling acid with 

 quantities of sea-water. The light of different spe- 

 cies is found to vary in character ; some of the sparks 

 being yellow and dull, others clearer and whiter, and 

 more lasting. The creature which produces the 

 brightest light of all is a kind of sea-worm {Nereis 

 ctrrigera) ; it lives in groups or large masses, among 

 the branches of sea-weed ; and when portions of this 

 are thrown on shore by the waves, the animals sur- 

 vive and continue to shine very brilliantly for several 

 days. In our own seas, a great deal of the light is 

 owing to the presence of an exceedingly minute 

 animal (Noctiluca yniliaris), which does not exceed 

 Toco P art °f an mcn m diameter. It consists of a 

 transparent globe, with a kind of tail proceeding 

 from one part of the circumference. In the interior 

 may be seen an oval nucleus, not in the centre, fron? 

 which proceed numerous branching vessels. The 

 luminous property appears to reside in these vessels 



