228 
POPULAR SCIENCE REVIEW. 
a mi sty -coloured light, which is usually greenish ; that of 
Italy is brilliantly blue ; whilst the Australian species emits a 
pulsating light. The fire-fly of the West Indies glows with a 
very white light ; but it is doubtful if the Fulgora , so often 
seen in books as the Lantern fly, has a scarlet light, or any at 
all. The rapid coruscating flashes on the sea and on the sands, 
are now and then yellow or white, but rarely scarlet, or reddish, 
and are produced by crustaceans. Other insects in the tropics 
give out a deep blue and white light ; and the Pacific Islands 
hundred-legs produce a brilliant emerald green. Noctiluca gives 
out a greenish and often bluish light, and the Medusoids vivid 
yellow, gold, green, blue and white tints. The Sea-pens give 
out white as well as coloured light ; and that of the Echino- 
derms is green. The green and white tints are the commonest 
colours, yellow is rare, and so are the reds and blues, whilst pur- 
ples are unusual. The Grorgonoids give out a beautiful lilac. 
A very slight examination of the animals connected with these 
luminous phenomena, indicates that they are produced in dif- 
ferent manners. For instance, Noctiluca , Pholas , and Lam- 
jpyris , are readily anatomized, and the source of the luminosity is 
found to differ in each. Hence it is important to consider some 
typical cases which illustrate the varieties of light-production. 
Consider, first of all, Noctiluca miliaris (PI. VI. figs. 1-3), 
which is very common in the warm summer months all round the 
English coast and up the Humber and Bristol Channel. It is im- 
possible to estimate the countless numbers of this minute, peach- 
shaped, flagellate infusorian in some parts of our seas. For 
instance, on the Essex coast some years since, I found every 
tumbler of sea-water taken out between the Grunfleet sands and 
the mainland, crowded with them ; and most of the actively- 
moving, little gelatinous transparent things were larger than 
their standard of -g^-th inch in diameter. They move by means 
of a filiform tentacle, of the length of the diameter of the body, 
and about y^o-th inch in its breadth, which is placed close to 
the opening of the so-called mouth. The tentacle is long and flat 
and has striations across it, but which appear to be beneath the 
delicate cuticle. A long, delicate, undulating fibril comes from 
the bottom of the oral cavity, and can be protruded and with- 
drawn, and close to it is a horny-looking, tooth-like body, T * 0 0 t h 
inch high. The opening into the interior, or mouth, is the 
extremity of a funnel, which ends within, in the minutely- 
granular substance forming the bulk of the body, and which, if 
it were perfectly transparent and uniform, no part being diffe- 
rentiated, might be called protoplasm. This granular sarcode I 
has spaces in it containing water, or vacuoles, one often being 
large, but they do not contract and enlarge like those of many 
Protozoa. Kadiating in meshes, which are coarse near the 
