FACTS AND THOUGHTS ABOUT LIGHT-EMITTING ANIMALS. 227 
there is a world of light, deep down below the surface. Great 
domes of pale gold with long streamers, move slowly along in end- 
less succession ; small silvery discs swim, now enlarging and now 
contracting ; and here and there a green or bluish gleam marks 
the course of a tiny but rapidly rising and sinking globe. Hour 
after hour the procession passes by ; and the fishermen hauling 
in their nets from the midst, drag out liquid light, and the soft 
sea-jellies, crushed and torn piecemeal, shine in every clinging 
particle. The night grows dark, the wind rises and is cold, and 
the tide changes, so does the luminosity of the sea. The pale 
spectres below the surface sink deeper, and are lost to sight ; 
but the increasing waves are tinged here and there with green 
and white ; and often along a line, where the fresh water is mix- 
ing with the salt in the estuary, there is a brightness so intense 
that boats and shores are visible. But if such sights are to be 
seen on the surface, what must not be the phosphorescence of 
the depths ? Every Sea-pen is glorious in its light ; in fact, 
nearly every eight-armed Alcyonian is thus resplendent ; and 
the social Pyrosoma , bulky and a free swimmer, glows like a 
bar of hot metal, with a white and green radiance. 
Just as in some places in England, the points of light on 
the turf may be seen, simultaneously, with the luminosity of 
the surface of the sea close by, so in the tropics, active and flying 
specks of brightness compete on shore with the diffused splen- 
dour off the coast. All this light, so vast in its world-wide 
amount, is heatless. Crowd it all together, and a vast city 
might be illuminated without raising the thermometer pro- 
bably many degrees, if at all ; and all this vibration, this con- 
sequence of intensely rapid molecular motion, is the result of 
the energy of life. 
The points of light on the turf of the South of England are 
produced by a beetle — the “ glowworm,” Lampyris ; and the 
genus is world-wide in its distribution. The fire-flies of the 
tropics are principally Elater beetles, and others allied to them 
in classification ; and there are Hemiptera as well as Myriopoda 
which add to the list. Our sea-surface illumination is due to 
myriads of Noctiluca miliaris , and the same and other species 
of the genus are world-wide. The minuter Crustacea, the Al- 
cyonarians, Medusae, Polyzoa, Ophiurans, Tunicata, Annelida, 
and Mollusca, add species to the luminous assemblage; and 
probably more than one hundred and fifty genera, most of which 
have numerous species which are prolific in individuals, are 
luminous under certain circumstances. It is possible that some 
fish noticed by Dr. Gunther are phosphorescent in the deep sea. 
The intensity and the colour of the light emitted, differ with 
the genus, species, locality, and season, and certain species 
have a definite and peculiar light. The English glowworm has 
