409 Observations on Luminous Animals. By J. MACARTNEY, Esq. (Phil. Trans. Part II. 1810.) THE property which certain animals possess of emitting light is so curious and interesting, that it has attracted the attention of naturalists in all ages. It was particularly noticed by Aristotle and Pliny amongst the ancients, and the publications of the different learned societies in Europe contain numerous memoirs upon the subject.. Notwithstanding the degree of regard bestowed upon the history of luminous animals, it is still very imperfect; the power of producing light appears to have been attributed to several creatures which do not possess it; some species which enjoy it in an eminent degree, have been imperfectly described or entirely unobserved; the organs which afford the light in certain animals have not been examined by dissection; and lastly, the explanations that have been given of the phænomena of animal light, are unsatisfactory, and in some instances palpably erroneous. As this subject forms an interesting part of the history of organized beings, I have for some years availed myself of such opportunities as occurred for its investigation. Having communicated the result of some of my researches to the Right Honourable Sir Joseph Banks, he immediately offered me his assistance with that liberality, which so eminently distinguishes him as a real lover of science. I am indebted to him for an inspection of the valuable journal he kept during his voyage with Captain Cook; for permission to copy the original drawings in his possession, of those luminous animals discovered in both the voyages of Cook; and for some notes upon the luminous appearance of the sea, that were presented to him by Captain Horsburg, whose accuracy of observation is already known to this learned So ciety. In the following paper, I shall first examine the grounds on which the property of shewing light has been ascribed to certain animals, that either do not possess it, or in which its existence is questionable. I shall next give an account of some luminous species, of which some have been inaccurately described, and others quite unknown. I shall endeavour to explain from my own observations, and the information communicated to me by others, many of the circumstances attending the luminous appearance of the sea. I shall then (No. 147.) 3 G describe describe the organs employed for the production of light in certain species; and lastly, I shall review the opinions which have been entertained respecting the nature and origin of animal light, and relate the experiments I have made for the purpose of elucidating this part of the subject. The property of emitting light has been reported to belong to several fishes, more particularly the mackarel, the moonfish (tetraodon mola,) the dorado, mullet, sprat, &c. Mr. Bajon observed during the migration of the dorados, &c. that their bodies were covered with luminous points. These however proved upon examination to be minute spher rical particles that adhered to the surface of these fishes; and, he adds, appeared to be precisely the same sort of points that illuminated the whole of the sea at the time. They were therefore in all probability the minute kind of medusa, which I shall have occasion to describe hereafter. Godelieu de Riville states, in a paper sent to the Academy of Sciences at Paris, that on opening the scomber pelamis while alive, he found in different parts of its body an oil which gave out much light: but it should be observed, that Riville had a particular theory to support, for which this fact was very convenient, and that other parts of his memoir bear marks of inaccuracy. It may be added, that if the oil of fishes were usually luminous, which Riville supposed, it would be almost universally known, instead of resting on a solitary observation,porato As far as I am able to determine from what I have seen, the faculty of exhibiting light during life does not belong to the class of fishes. It appears probable, that some fishes may have acquired the character of being luminous, from evolving light soon after death. Some species of lepas, murex, and chama, and some star. fish have been said to possess the power of shining and the assertion has been repeated by one writer after another, but without quoting any authority. Brugueire upon one occasion saw, as he supposed come mon earth worms in a luminous state; all the hedges were filled with them; he remarked that the light resided principally in the posterior part of the body.* 01.77 59921. Flaugergues pretended to have seen earth worms luminous in three instances; it was at each time in October; the body! shone at every part, but most brilliantly at the genital organs, To t * Journal d'Histoire Naturelle, Tom. II. 15017013 Notwithstanding Notwithstanding this concurrence of testimony, it is next to impossible, that animals so frequently before our eyes as the common earth worm, should be endowed with so remarkable a property, without every person having observed it. If they only enjoyed it during the season for copulation, still it could not have escaped notice, as these creatures are usually found joined together in the most frequented paths, and in the garden walks. In different systems of natural history, the property of shining is attributed to the cancer pulex. The authorities for this opinion are Hablitzl, and Thules and Bernard. The former observed upon one occasion, a cable that was drawn up from the sea exhibit light, which upon closer inspection was perceived to be covered by these insects.* Thules and Bernard reported that they met with a number of this species of cancer on the borders of a river, entirely luminous. I am nevertheless disposed to question the Inminous property of the cancer pulex, as I have often had the animal in my possession, and never perceived it to emit any light. The account given by Linneus of the scolopendra phosphorea, is so improbable and inconsistent, that one might be led to doubt this insect's existence, particularly as it does not appear to have been ever seen, except by Ekeberg, the Captain of an East Indiaman, from whom Linneus learnt its history. I now proceed to the description of those luminous animals that have been discovered by the Right Honourable Sir Joseph Banks, Captain Horsburg, and myself. On the passage from Madeira to Rio de Janeiro, the sea was observed by Sir Joseph Banks to be unusually luminous, flashing in many parts like lightning. He directed some of the water to be hauled up, in which he discovered two kinds of animals that occasioned the phenomenon; the one, a crustaceous insect which he called the cancer fulgens; the other, a large species of medusa, to which he gave the name of pellucens. The cancer fulgens bears some resemblance to the common shrimp; it is however considerably less; the legs are furnished with numerous setæ. The light of this animal, which is very brilliant, appears to issue from every part of the body. The medusa pellucens measures about six inches across the crown or umbella; this part is marked by a number of opake *Hablitzl ap. Pall. n. Nord. Beytr. 4, p. 396, Journal de Physique, Tome XXVIII. lines, lines, that pass off from the center to the circumference. The edge of the umbella is divided into lobules, which succeed each other, one large and two small ones alternately. From within the margin of the umbella, there are suspended a number of long cord-shaped tentacula. The central part of the animal is opake, and furnished with four thick irregularly shaped processes, which hang down in the midst of the teutacula. $.. This zoophyte is the most splendid of the luminous inhabitants of the ocean. The flashes of light emitted during ..its contractions, are so vivid as to affect the sight of the spectator. In the notes communicated to Sir Joseph Banks by Cap.tain Horsburg, he remarks that the luminous state of the sea 23 between the tropics, is generally accompanied with the apsapearance of a great number of marine animals of various kinds upon the surface of the water: to many of which he does not, however, attribute the property of shining. At other times, when the water which gave out light was exvamined, it appeared only to contain small particles of a dusky straw colour, which dissolved with the slightest touch of the finger. He likewise observes, that in Bombay, durving the hot weather of May and June, he has frequently seen athe edges of the sea much illuminated by minute sparkling points to dana 1945, se anchumer it to di Atsun-rise on April 12, 1798, in the Arabian sea, che perceived several luminous spots in the water, which conceiving to be animals, he went in the boat and caught one. It proved to be an insect somewhat resembling in appearance the wood dalouse, and was about one third of an inch in length. When viewed with the microscope, it seemed to be formed by sections of a thin crustaceous substance. During the time that any fluid remained in the animal, it shone brilliantly like the fire fly.sto 15qbq Pomelos-dich sleIn the month of June in the same year, he picked up another luminous insect on a sandy beach, which was also covered with a thin shell, but it was a different shape, and a larger size than the animal taken in the Arabian sea. w51 3719200 9DW TH By comparing the above description with an elegant pen and ink drawing which was made by Captain Horsburg, and accompanied his paper, I have no doubt that both these insects were monoculi; the first evidently belongs to the genus limulus of Muller; I shall therefore beg leave to distinguish it by the name of limulus noctilucus.. My pursuits, and the state of my health, having frequently led me to the coast, 1 have had many opportunities of making observations upon the animals which illuminate our Own own seas of these I have discovered three species: one of which is a beroe not hitherto described by authors; another agrees so nearly with the medusa hemispherica, that I conceive it to be the same, or at least a variety of that species; the third is a minute species of medusa, which I believe to be the luminous animal, so frequently seen by navigators, although it has never been distinctly examined or scribed. i I first met with these animals in the month of October 1804, at Herne Bay, a small watering place upon the northern coast of Kent. Having observed the sea to be extremely luminous for several nights, I had a considerable quantity of the water taken up. When perfectly at rest, no light was emitted, but on the slightest agitation of the vessel in which the water was contained, a brilliant scintillation was perceived, particularly towards the surfaces; and when the vessel was suddenly struck, a flash of light issued from the top of the water, in consequence of so many points shining at the same moment. When any of these sparkling points were removed from the water, they no longer yieldedmany light. They were so transparent, that in the air they hppeared like globules of water. They were more minute than the head of the smallest pin. Upon the slightest touch they broke and vanished from the sight. Having strained a quantity of the luminous water, a great number of these transIparent corpuscles were obtained upon the cloth, and the water which had been strained did not afterwards exbibit bsthedeast light. I then put some sea water that had been rendered particularly clear, by repeated filtrations, into a large glass, and having floated in it no fine cloths on which I had previously collected a number of luminous points, several of them were liberated, and became distinctly visible in [their natural element, by placing the glass before a piece of dark coloured paper. They were observed to have antendency to come to the surface of the water, and after the glass was set by for some time, they were found congregated together, and when thus collected in a body, they had a dusky straw colour, although individually they were so transparent as to be perfectly invisible, except under particular circumstances. Their substance was indeed so extremely tender and delicate, that they did not become opaque in distilled vinegar or alcohol, until immersed in these liquors for a considerable timed Male 1. milu lo aulumi! 6 I On examining these minute globules with the microscope, I found that they were not quite perfect spheres, but had an irregular depression on one side, which was formed of an opaque substance, that projected a little way inwards, pro ducing |