316 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 Meduse, torn but 
yet living, as in some cases fragments of these ani- 
mals are very tenacious of life, Several-minute Me- 
duse 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 poimt 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 isa kind of sea-worm (Nereis 
cirrigera); 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 miliaris), which does not exceed 
zéoo part of an inch in 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, from 
which proceed numerous branching vessels, The 
luminous property appears to reside in these vessels, 
