PHOSPHORESCENCE. The phenomenon of phosphorescence, Dr. Hooker says, is very con spicuous on stacks of firewood, at Darjiling, during tho clamp, warm, summer months, May to October, at elevations of 5000 to 8000 feet; it may be witnessed every night by penetrating a few yards into the forest,—at least it was so in 1848 and 1849 ; and during Dr. Hooker's stay there, billets of decayed wood were repeatedly sent to him by residents, with inquiries as to the cause of their luminosity. A stack of firewood pre sented a beautiful spectacle for two months (in July and August), and on passing it at night, Mr. Ilodgson had to quiet his pony, who was always alarmed by it. The phenomenon in variably accompanies decay, and is common on oak, laurel, Tetranthera, birch, and probably other timbers ; it equally appears on cut wood and on stumps, but is most frequent on branches lying close to the ground in the wet forests. It is a vital phenomenon, and due to the myce lium of a fungus. Alcohol, heat, and dryness soon dissipate it. In the animal kingdom, luminos ity is especially common amongst the radiata and inollusca ; it is also frequent in the entromos tracous crustacea, and in various genera of most orders of insects. In all these, even in the ser tularim, Dr. Hooker observed the light to be increased by irritability, in which respect the luminosity of animal life differs from that of vegetable. Phosphorescent matter is secreted or emitted at will by an infinite number of crustacean and molluscous animals, with which the ocean abounds, but has been observed to obtain also in a species of shark, and in the glow-worm, fire fly, and the luminous centipede, Geophilus fulgens, one of the myriapoda. It also exists in some fungoid plants ; a species of agaricus in the Australian woods is vividly luminous, and is described by Dr. Hooker as occurring at Dar jiling. Dr. F. D. Bennett was inclined to believe that phosphorescence of the sea is caused from a luminous power in living marine animals. Some times the sea for miles gives at night a pale light from myriads of noctiluca. The commonest phos phorescence is caused by various small animals, small crustaceans. Some crustacea certainly derive their phosphorescence from containing in their stomachs phosphorescent food, and their excrement is phosphorescent. When largo fish or porpoises or penguins dash through water full of luminous crustaceans or noetiluea, their bodies are brilliantly lit up, and their track marked with a trail of light. The Ascidian colony pyro , soma, however, gives the most beautiful phos phorescence. When touched, the light breaks out at first at the spot stimulated, and then spreads over the surface of tho colony as the stimulus is transmitted to the surrounding aniinala.
The pyrosoma is a pelagic aggregation of indi viduals, forming a hollow cylinder closed at one end, from 5 inches to 5 feet in length. The
pyrosoma Atlanticum, from 3 to 4 inches long, is composed of an aggregation of small tunicaries, and produces a powerful light on being dis turbed. Large forms of Aurelia and Cyanea move along, surrounded by a halo of golden greenish light. The little Dysmorphoaa gives a light of a deep aurelian hue. A large jelly-ftsh (Medusa) was observed near Nantucket, from the mast of a vessel, moving lazily along, its disk encircled by a halo of 20 feet in diameter, while the train of gleaming tentacles stretched away 200 feet or more. Mrs. Agassis measured one whose disk was 7 feet across, with tentacles over 112 feet in length. The shapely Zygodactylm wander about like ignes fatui ; the Idylia gleams with ever-changing hues ; pleuro-branchim flit about, their fringed tentacles glistening with red, green, yellow, and purple rays. Urticena nodosa is a luminous sea anemone of New England. Noctilucre zones occur 30 miles in breadth, about 30,000 in a cubic foot ; the diatom pyrocistis, the star-fishes, Asterias ophiocnida, species of Ophiuridm, and others, are luminous, and amongst others may be named the moon-fish, Orthagoris cus mola ; the lamp-fish, Scopelus resplendens; species of Chauliodusargyropelecus, and tho Squa lus fulgens of Florida. The sea-pen, Renilla reni form* emits a golden-green light. The Penna tula phosphorea sea-pen emits a vivid purple light ; also species of the little pterypod Cleadora. Pyrocistis fusiformis is the lantern fish. Cirra tulus grandis is a marine worm of Great Britain. Cancer fulgens of the Atlantic sends out flashes of light, especially when irritated.
All the alcyonarians dredged by the Challenger in deep water were found to be brilliantly phos phorescent when brought to the surface.
The polyps of the Veretillum cynomorium, a zoophyte of the Mediterranean and Atlantic, is phosphorescent. At night, on the slightest irri tation, a whole colony glows with undulating waves of pale green phosphoric light.
:Medusa; possess luminous powers. The Snipe are luminous. The Squalus fulgens, or luminous shark, gives out a shining light like that of the pyrosoma. Dr. Bennett found the surface of the water become brilliantly phosphorescent, when his boat struck on a coral reef at Thur Bay in the island of Rotuma. One of the pyrosoma, a lumin ous aggregate tunicated mollusc, has been found there floating in great numbers; and little minute) points, apparen tly of a jel ly-li ke subs tanee, are found on the Australian coast, similar to those which on the coasts of England have been called noctiluca.
Kirby and Spence state that a ground beetle (Carabus) has been observed running round and i round a luminous centipede as if afraid to attack it.
A nocturnal ape, the Nyctipithecus trivirgatus, is said to emit light from the eyes.—Nose ley, p. 574; Bennett, p. 64; Hooker's him. J. in p. 150; P. 71 ; Jameson's Journ. xi. p. 222, 1824.