The statement which has been often repeated since Spallanzani, that the diœcious common hemp (Cannabis sativa) yields perfect seeds without the neighbourhood of pollen-bearing vessels, has been refuted by later experiments. When seeds have been obtained, anthers in a rudimentary state, capable of furnishing some grains of fertilizing dust, have been discovered near the ovarium. Such hermaphroditism is frequent in the entire family of Urticeæ, but a peculiar and still unexplained phenomenon has been presented in the forcing-houses at Kew by a small New Holland shrub, the Cœlebogyne of Smith. This phænogamous plant produces in England perfect seeds without trace of male organs, or the hybridising introduction of the pollen of other species. An ingenious botanist, Adrien de Jussieu, in his “Cours Elementaire de Botanique,” 1840, p. 463, expresses himself on the subject as follows:—“Un genre d’Euphorbiacées (?) assez nouvellement décrit mais cultivé depuis plusieurs années dans les serres d’Angleterre, le Cœlebogyne, y a plusieurs fois fructifié, et ses graines étaient évidemment parfaites, puisque non seulement on y a observé un embryon bien constitué, mais qu’en le semant cet embryon s’est développé en une plante semblable. Or les fleurs sont dioïques; on ne connait et ne possède pas (en Angleterre) de pieds mâles, et les recherches les plus minutieuses, faites par les meilleurs observateurs, n’ont pu jusqu’ici faire découvrir la moindre trace d’anthères ou seulement de pollen. L’embryon ne venait donc pas de ce pollen, qui manque entièrement: il a dû se former de toute pièce dans l’ovule.”
In order to obtain a fresh confirmation or elucidation of this highly important and isolated phenomenon, I addressed myself not long since to my young friend Dr. Joseph Hooker, who, after making the Antarctic voyage with Sir James Ross, has now joined the great Thibeto-Himalayan expedition. Dr. Hooker wrote to me in reply, on his arrival at Alexandria near the end of December 1847, before embarking at Suez: “Our Cœlebogyne still flowers with my father at Kew as well as in the Gardens of the Horticultural Society. It ripens its seeds regularly: I have examined it repeatedly very closely and carefully, and have never been able to discover a penetration of pollen-tubes either in the style or ovarium. In my herbarium the male blossoms are in small catkins.”
[5] p. 7.—“Shine like stars.”
The luminosity of the ocean is one of those superb natural phenomena which continue to excite our admiration even when we have seen them recur every night for months. The sea is phosphorescent in every zone; but those who have not witnessed the phenomenon within the tropics, and especially in the Pacific, have only an imperfect idea of the grand and majestic spectacle which it affords. When a man-of-war, impelled by a fresh breeze, cuts the foaming waves, the voyager standing at the ship’s side feels as if he could never be satisfied with gazing on the spectacle which presents itself to his view. Every time that in the rolling of the vessel her side emerges from the water, blue or reddish streams of light appear to dart upwards like flashes of lightning from her keel. Nor can I describe the splendour of the appearance presented on a dark night in the tropic seas by the sports of a troop of porpoises. As they cut through the foaming waves, following each other in long winding lines, one sees their mazy track marked by intense and sparkling light. In the Gulf of Cariaco, between Cumana and the Peninsula of Maniquarez, I have stood for hours enjoying this spectacle.
Le Gentil and the elder Forster attributed the flashing to the electric friction excited by the ship in moving through the water, but the present state of our knowledge does not permit us to receive this as a valid explanation. (Joh. Reinh. Forster’s Bemerkungen auf seiner Reise um die Welt, 1783, S. 57; Le Gentil, Voyage dans les Mers de l’Inde, 1779, T. i. p. 685-698.)
Perhaps there are few natural subjects of observation which have been so long and so much debated as the luminosity of the waters of the sea. What we know with certainty on the subject may be reduced to the following simple facts. There are several luminous animals which, when alive, give out at pleasure a faint phosphoric light: this light is, in most instances, rather bluish, as in Nereis noctiluca, Medusa pelagica var. β (Forskäl, Fauna Ægyptiaco-arabica, s. Descriptiones animalium quæ in itinere orientali observavit, 1775, p. 109), and in the Monophora noctiluca, discovered in Baudin’s expedition, (Bory de St.-Vincent, Voyage dans les Iles des Mers d’Afrique, 1804, T. i. p. 107, pl. vi.) The luminous appearance of the sea is due partly to living animals, such as are spoken of above, and partly to organic fibres and membranes derived from the destruction of these living torch-bearers. The first of these causes is undoubtedly the most usual and most extensive. In proportion as travellers engaged in the investigation of natural phenomena have become more zealous in their researches, and more experienced in the use of excellent microscopes, we have seen in our zoological systems the groups of Mollusca and Infusoria, which become luminous either at pleasure or when excited by external stimulus, increase more and more.
The luminosity of the sea, so far as it is produced by living organic beings, is principally due, in the class of Zoophytes, to the Acalephæ (the families of Medusa and Cyanea), to some Mollusca, and to a countless host of Infusoria. Among the small Acalephæ, the Mammaria scintillans offers the beautiful spectacle of, as it were, the starry firmament reflected by the surface of the sea. This little creature, when full grown, hardly equals in size the head of a pin. Michaelis, at Kiel, was the first to show that there are luminous siliceous-shelled infusoria: he observed the flashing light of the Peridinium (a ciliated animalcule), of the cuirassed Monad the Prorocentrum micans, and of a rotifera to which he gave the name of Synchata baltica. (Michaelis über das Leuchten der Ostsee bei Kiel, 1830, S. 17.) The same Synchata baltica was subsequently discovered by Focke in the Lagunes of Venice. My distinguished friend and Siberian travelling companion, Ehrenberg, has succeeded in keeping luminous infusoria from the Baltic alive for almost two months in Berlin. He shewed them to me in 1832 with a microscope in a drop of sea-water: placed in the dark I saw their flashes of light. The largest of these little infusoria were 1-8th, and the smallest from 1-48th to 1-96th of a Paris line in length (a Paris line is about nine-hundredths of an English inch): after they were exhausted, and had ceased to send forth sparkles of light, the flashing was renewed on their being stimulated by the addition of acids or of a little alcohol to the sea-water.
By repeatedly filtering water taken up fresh from the sea, Ehrenberg succeeded in obtaining a fluid in which a greater number of these luminous creatures were concentrated. (Abhandlungen der Akad. der Wiss. zu Berlin aus dem J. 1833, S. 307; 1834, S. 537-575; 1838, S. 45 and 258.) This acute observer has found in the organs of the Photocaris, which emits flashes of light either at pleasure or when irritated or stimulated, a cellular structure with large cells and gelatinous interior resembling the electric organs of the Gymnotus and the Torpedo. “When the Photocaris is irritated, one sees in each cirrus a kindling and flickering of separate sparks, which gradually increase in intensity until the whole cirrus is illuminated; until at last the living fire runs also over the back of the small Nereis-like animal, so that it appears in the microscope like a thread of sulphur burning with a greenish-yellow light. It is a circumstance very deserving of attention, that in the Oceania (Thaumantias) hemisphærica the number and situation of the sparks correspond exactly with the thickened base of the larger cirri or organs which alternate with them. The exhibition of this wreath of fire is a vital act, and the whole development of light is an organic vital process which in the Infusoria shows itself as an instantaneous spark of light, and is repeated after short intervals of repose.” (Ehrenberg über das Leuchten des Meeres, 1836, S. 110, 158, 160, and 163.)
According to these suppositions, the luminous creatures of the ocean show the existence of a magneto-electric light-evolving process in other classes of animals than fishes, insects, Mollusca, and Acalephæ. Is the secretion of the luminous fluid which is effused in some luminous creatures, and which continues to shine for some time without any farther influence of the living animal (for example, in Lampyrides and Elaterides, in the German and Italian glow-worms, and in the South American Cucuyo which lives on the sugar-cane), only a consequence of the first electric discharge, or is it simply dependent on chemical mixture? The shining of insects surrounded by air has doubtless other physiological causes than those which occasion the luminosity of inhabitants of the water, fishes, Medusæ, and Infusoria. The small Infusoria of the ocean, being surrounded by strata of salt water which is a good conducting fluid, must be capable of an enormous electric tension of their light-flashing organs to enable them to shine so intensely in the water. They strike like Torpedos, Gymnoti, and the Tremola of the Nile, through the stratum of water; while electric fishes, in connexion with the galvanic circuit, decompose water and impart magnetism to steel bars, as I showed more than half a century ago (Versuche über die gereizte Muskel- und Nervenfaser, Bd. i. S. 438-441, and see also Obs. de Zoologie et d’Anatomie comparée, vol. i. p. 84); and as John Davy has since confirmed (Phil. Trans, for 1834, Part ii. p. 545-547), do not pass a flash through the smallest intervening stratum.
The considerations which have been developed make it probable that it is one and the same process which operates in the smallest living organic creatures, so minute that they are not perceived by the naked eye,—in the combats of the serpent-like gymnoti,—in flashing luminous infusoria which raise the phosphorescence of the sea to such a degree of brilliancy;—as well as in the thunder-cloud, and in the auroral, terrestrial, or polar light (silent magnetic lightnings), which, as the result of an increased tension in the interior of the globe, are announced for hours beforehand by the suddenly altered movements of the magnetic needle. (See my letter to the Editor of the Annalen der Physik und Chemie, Bd. xxxvii. 1836, S. 242-244).