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The eggs of Lacerta agilis and of some serpents emit a beautiful green light; the fresher they are, the more brightly they shine. When buried in moderately damp earth, they go on shining for weeks; exposed to the air, they become dry and soon lose their phosphorescence. (Langrebe.) Non-luminous eggs become luminous by agitation. (Gründler, Naturforscher, 3, 28.)

In the Elater, there are two elongated and roundish luminous spots on each side of the dorsal covering. These are glands containing a yellow substance; and to these the animal, by means of branches proceeding from the cells of the lungs, can allow a large or small quantity of air, or none at all to have access, whereby the development of light is made stronger or weaker, or ceases altogether. The animal shines for six or eight days, even on the needle. (Spex. Comp. Illiger, Mag. d. Ges. naturf. Freunde zu Berlin. 1807, 141.)

The female of Lampyris noctiluca or splendidula (the glow-worm), whose abdomen is divided into six segments, shines on the under part of the last three abdominal rings, which are distinguished by a yellowish or greenish white colour from the brown-coloured parts of the rest of the body. Within these threo terminal rings is found the luminous matter, a yellowish wbite transparent substance, consisting of ramifying fibres and granules of an organic structure, heavier than water, yellow and opaque when dry, and consisting principally of a material which exhibits the chemical properties of soluble albumen. (According to Heinrich, an adhesive luminous substance, which imparts its phosphorescent properties to water or oil, may be squeezed out of the animal; according to Macartney, this substance when separated from the animal is no longer luminous, whereas the bag containing the luminous matter shines, when separated from the animal, for several hours in the air, and for 48 hours in water.) The phosphorescence of the animal begins about 7 or 8 o'clock in the evening and continues. till sunrise. (According to Macartney, a thermometer rises when placed in contact with the insects while emitting light, but not when in contact with the separated luminous matter of the tail.) The phosphorescence of the insect is totally unaffected by want of food, or by storms, thunder, or candle-light. It is strengthened by repeated gentle disturbance, and is most vivid during the motion of the animal. It is interrupted for a time by sleep, noise, mere violent disturbance, or by cooling to + 12 C° (53-5° Fah.),--and then the phosphorescence ceases from the fore to the back part, two points on the terminal ring often however continuing to glow. The luminous matter, when kept under water, continues to shine for two or three days. If a living worm be placed in water, at 14° C, and the liquid warmed, the animal begins to shine at 27", emits the strongest light at 41°; continues shining, though dead, at a higher temperature, and its light is extinguished for ever at 57° or 62°. If the temperature of the water be maintained at 35°, the animal continues to shine for a long time after death, but gradually ceases when the water is cooled to 25°. When the insect is warmed without water, the same effect is observed, excepting that the phosphorescence ceases sooner, on account of the drying up of the luminous matter. Dead glow-worms, not yet dry, begin to shine again in water at 44°, and often remain luminous for two or three days after the cooling of the water. Glow-worms killed by cooling them to 0° begin to shine again at 31°. If the head or the luminous ring of a worm which shines of itself be cut off, the light ceases in about five minutes, but re-appears in a few minutes longer in a lower degree, continuing for two or three days, and may be strengthened at

pleasure by warming. The phosphorescence of the extracted luminous matter may likewise be strengthened by moderate heating, and destroyed by a heat of 53°,-in which respect it resembles coagulated albumen. A current of electricity from the electrical machine, or repeated electrical discharges passed through the animal, excite no phosphorescence. If, on the contrary, the insect immersed in a little water be brought by means of two wires within the circuit of the voltaic pile, it instantly becomes luminous and continues so as long as the circuit is complete, but ceases to shine every time the circuit is broken, although the water surrounding the animal shows an elevation of temperature of only lo. Similar effects are produced upon decapitated glow-worms, on the three terminal rings, and the separated luminous matter, when they are no longer selfluminous.— Neither the animal nor the luminous matter is phosphorescent in vacuo, even at the most favourable temperature or under the influence of the voltaic pile; on admitting the air, the luminosity is restored. The phosphorescence of the luminous matter likewise ceases under oil, probably because the access of air is impeded. In oxygen gas and nitrous oxide, the glow-worm appears to shine somewhat more brightly than in common air. (The increased luminosity in oxygen gas was observed by Spallanzani (Gilb. 1, 33) and by Forster. According to Grotthuss, the animals must be cooled some degrees lower in oxygen gas than in common air before they lose their phosphorescence.) In chlorine gas the animal dies instantly, and if subsequently warmed, emits a rose-coloured light for a short time. In hydrogen, carbonic acid, carburetted hydrogen, or sulphurous acid gas, the glow-worm soon dies and emits no light when warmed. According to Spallanzani, also, the light is extinguished gradually in nitrogen and hydrogen gas and instantly in carbonic acid. The luminous matter also loses its phosphorescence in these gases, and shines again on the admission of air or oxygen gas, excepting when the luminosity has been destroyed by chlorine, sulphurons acid, or vapour- of hypo-nitric acid.—Alcohol and very dilute mineral acids, which do not kill the animal instantly, cause the final extinction of its light when under water, and likewise of that of the extracted luminous matter; concentrated acids extingnish it instantly. By these means, as well as by heating, or by the action of copper-salts, corrosive sublimate or ether, the luminous matter passes into the state of coagulated albumen, and then its luminosity is destroyed. In aqueous solution of potash the luminous matter dissolves and loses its illuminating power. (Macaire.)

The Lampyris shines both as a perfect insect and also in the larva state, but most powerfully in the nymph state. (De Geer.) The eggs begin to shine faintly in four or six weeks, when the larvæ are developed and on the point of emerging. The females shine with peculiar brightness in the breeding-season and during procreation, cease to shine immediately afterwards, but shine brightly again on the following evening; their light is brightest when they are pregnant, at which time they emit light from their whole bodies with the exception of the head. The males do not shine during procreation. (Langrebe.)

The Lampyris Italica shines under water for several hours, under oil for only 20 minutes; it soon loses its phosphorescence when immersed in hydrogen, carbonic acid, or nitric oxide gas, but shines again when brought out into the air, provided luminosity has not been too long interrupted; but in this case the insect shines, even when dead, in hyponitric acid vapour, emitting a green light which slowly disappears. (Carradori.)

The female of Lampyris Italica exhibits the same steady light as that

of the L. noctiluca. But the male, whose two hinder abdominal rings are perfectly luminous, exhibits a flashing light, becoming brighter from 45 to 55 times in a minute, in accordance with the number of pnlsations in the same interval. The luminous substance is situated immediately on the lower segments of the two hinder abdominal rings, exactly in the position where the pulsation of the dorsal vessel is the strongest. The blood may in this situation strengthen the phosphorescence, in consequence of the lubrication, vital influence, and excess of oxygen which it causes. The luminous matter separated from the animal is white and viscid, appears under the microscope to consist entirely of small globules, between which are distributed numerous tracheal ramifications,-shines when spread upon glass, with a greenish light, which diminishes and ultimately ceases when the matter becomes dry, but may often be restored by moisture. (Carus.)

In Pausus, the antenne alone emit a feeble light. (Afzelius.)

In Fulgora, the light proceeds from the hollow projection situated on the hinder part of the head, and connected with the air-vessels.

Scolopendra shine over the whole body.

The Nereis shines most conspicuously when the sea is agitated by the passage of ships and other causes (Spallanzani); its luminous matter may be diffused through water (Treviranus). According to Viviani, the cirrigera is the most luminous of all animals inhabiting the Mediterranean.

Lumbricus terrestris sometimes shines in October on the indurated ring. (Brugière, Flaugergues, J. Phys. 16, 311; Andouin, Institut. 1840, 381.)

Planaria retusa shines uniformly over the whole body. (Viviani).

The Pholas Dactylus, boring muscle, also contains a phosphorescent liquid which adheres to everything which it touches and makes it Juminous, and may be expressed and mixed with water, oil, or milk, so as to form a luminous fluid. The boring muscle not only shines externally, but likewise internally when cut open ; it continues to shine for a day or two after death, till it putrefies. Its light shows itself between 0° and 56°; gentle heating strengthens it but shortens its duration ; stronger heating destroys it. The phosphorescence of muscles becomes brighter in dilute solutions of common salt, nitre, potash, and sugar; it is destroyed by sulphuric acid, vinegar, alcohol, and urine, and by concentrated solutions of potash, sal-ammoniac, salts of lead, and vitriol. Dried pholades recover their luminosity on being moistened with water, even after the lapse of several months. (Beccaria, Comment. Bonon. 2, 1, 248.)

Salpæ (according to Edw. Forbes, Ann. and Mag. of Nat. Hist., 1841, 7, 350) do not shine of themselves, but only in consequence of luminous crustacea which frequently adhere to them.

Pyrosoma Atlanticum diffuses a very vivid light, and is often so abundant in the sea that fish can be distinguished by its light at the depth of 15 feet. The temperature of water in which this animal is immersed rises about 1° C., as is likewise the case with Salpæ. (Kuhl, Schw. 34, 364.)

The light of Asterias noctiluca spreads itself out from the centre into the rays: the separated rays and their fragments also continue luminous for a time. (Viviani.)

The luminous parts of the Medusæ observed by Spallanzani are: the large tentacula, the edge of the umbella, and the sac which is connected with the opening of the umbella. These parts contain the luminous principle in the form of a thickish glutinous liquid, very different from the saline watery fluid into which the medusa almost entirely melts when removed from the water. This viscid liquid produces itching when applied to the skin, as does also the juice of several non-luminous medusæ. The luminous matter may be scraped off—renders bodies smeared with it phosphorescent—and when mixed with water, urine, and particularly with milk, forms mixtures which remain luminous for several hours—are increased in brightness by agitation or by warming to 37°C.-may be again rendered luminous after their phosphorescence has ceased—but when strongly heated, are deprived of their luminosity for ever. (Luminous fluids of this kind may also be obtained by mashing up the entire animal in water; if sea-water is used for the purpose, the mixture shines but feebly.)—The medusa shines in water like a torch, so brightly that it can be seen at the distance of 100 paces. Its light is most brilliant when the alternate contraction and enlargement of the disc succeed each other with the greatest rapidity; the light is also strengthened by motion from without. With the diminution of this oscillation the light becomes fainter, and when it ceases, there remains only a very faint luminosity, which may also be observed after death, and does not disappear till putrefaction sets in; it is likewise increased for a time by rubbing. A medusa which has died out of water, and is no longer luminous but beginning to deliquesce, recovers its luminosity in fresh, but not in sea water: the water also becomes luminous. (Spallanzani.)

The luminosity of Medusa lucida in water is increased by warming, till the water becomes so hot as to kill the animal. In alcohol it shines still more brightly, but soon dies and ceases to be luminous. Placed in water under an exhausted receiver, it shines as strongly as under the ordinary pressure of the air. The electric spark seems to have no action upon it; electric shocks cause the light to disappear for an instant, but it immediately reappears with increased brightness. (Macartney.)

In Aurelia, the light proceeds from the base of the tentacula; in Beroë from the vessels under the laced filaments. (Edw. Forbes.)

If a Physalia be immersed in alcohol it instantly ceases to shine, because it dies.—Zoophytes do not shine when at rest, but only after exertion, and consequently increased respiration, inasmuch as locomotion and respiration are with these animals one and the same movement. Their light becomes fainter as their vital force diminishes, and ceases with their death. This takes place after often repeated exertion and luminosity thence resulting. (Tilesius.)

In the Pennatula phosphorea, the light proceeds, not from the stem, but only from the feather and is excited only by motion, either spontaneous or induced from without. After death, luminosity is produced by touching the animal, a luminous slime being at the same time expressed from the feather. (Spallanzani.)

In Alcyonum exos, likewise, the phosphorescence exists not in the stem, but in the individual polypi. (Leuckardt.)

The phosphorescence of the sea at night—which sometimes diffuses a universal but dull glimmer of light, sometimes presents a fiery surface, at other times shines only in places where it is set in motion by ships or oars, at others again exhibits single sparks, stars, balls, chains, or bands of fire-is mainly attributable to small luminous animals which inhabit the sea. The separate luminous spots are produced by the larger Medusæ, Salpæ, and Pyrosomæ, which emit the most vivid light. (Tilesius.) The general luminosity of the sea is produced by various animals, but more especially by small crustacea whose light is of a sparkling character, by

Nereids, and great numbers of small Meduse. When sea-water of this nature is filtered, the luminous matter remains on the filter. (Sparmann, Tilesius.) Water taken out of the brightly-shining sea near Martinique gave no light when at rest; on blowing upon it, small bodies crossed the liquid in all directions, shining the brighter the more strongly the surface was blown upon. When stirred, the water became luminous throughout: on being warmed to 35o C. it also became brightly phosphorescent; but when further heated to 43°, its luminosity was completely destroyed. Hydrochloric, sulphuric, and nitric acid, ammonia, carbonate of potash, and alcohol likewise produced a sudden and generally evanescent light. The water after passing through a filter could no longer be rendered luminous: there remained on the filter a number of small animals discernible by the microscope, and consisting of a globule having a yellow spot and a tail, which they moved with great rapidity. (Artaud.)- Moreover, the phosphorescence of the sea is probably often produced by the luminous putrefaction of marine animals, by insolation (as appears to be the case from an experiment of Hellwig), and by electricity, as supposed by Rivière, Le Gentil, and Bajon.

Instances have been known of men whose perspiration is adhesive and phosphorescent, so that the phosphorescence is communicated to their linen; the smell of this perspiration, in the case of an individual of gouty diathesis, in whom the perspiration broke out after violent dancing, was urinous and sour (Henkel, Crell. N. Chem. Archiv. 2, 291); in another it had a peculiar phosphoric odour. (Hermstadt, Magaz. naturf. F. 2, 248.) Horses in the sweating condition sometimes emit light. Percy saw the wounds on a soldier's thigh continue phosphorescent for fourteen days; over the wounds of another, he saw a light like an ignis fatuus hover for

More frequently human urine just voided exhibits phospho. rescence. (Jurine, Driessen, Gilb. 49, 291; 59, 262.)-Esser (Kastn. Archiv. 8, 414) saw the urine which he voided against the wall, when tired after a walk, exhibit phosphorescence; the wall shone for half a minute as if it had been smeared with phosphorus: the urine discharged two hours later was not phosphorescent. The urine of Viverra Putorius and Mephitis is likewise said to be luminous at the moment at which these animals void it. (F. D'Azora, Langsdorff.) The luminosity of the eyes of animals is due merely to reflected light. (Esser, Kastn. Archiv. 8, 399.)

six days.

II. Phosphorescence of Living Plants.

1. Sudden emission of Light. A sudden flashing light is often emitted, on fine summer evenings, a little after sunset, by certain yellow flowers.

Such is the case with Tropaeolum majus, Tagetes patula and erecta, Calendula officinalis, Helianthus annuus, Lilium bulbiferum and Chalcedonicum, Polyanthes tuberosa, Oenothera biennis and Gorteria ringens: likewise Papaver orientale. (Elis. Linné, Abhandl. d. Schwed. Akad. 24, 291.-Haggren, N. Abhandl. d. Schwed. Akad. 9, 59.—Johnson, Schw. 31, 361.-Pursch, Flor. Amer, Septentr. 1, 261.-Green, J. Pharm. 18, 256.) Of these, Calendula emits the strongest light; then follows Trapaeolum, then Lilium bulbiferum and Tagetes patula, then Helianthus and Garteria. The same flower often gives out repeated flashes at intervals of several minutes. This light is undoubtedly electrical, perhaps

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