APPENDIX.
[1] Page 5.—Noctiluca. This interesting little creature belongs, in the natural arrangement as now recognized by science, to the first grand division of the animal kingdom. Simple as it is, it is not so completely without organs as some which form the first groups of this first division, as it has a whip-like organ, which gives name to its group, the Flagellata, or flagellate infusorians. These monads, as they are also called, are represented by a species of Noctiluca in our North-American waters off the coast of Maine. Huxley regards its luminous property as given out by the peripheral layer of protoplasm which lines the cuticle.
M. Giglioli of Bologna, Italy, in a letter to the author, says, “I have distinguished three modes of marine phosphorescence, very distinct, which present a great number of varieties. These are,—
“(a) Diffused homogeneous milky light.
“(b) Luminous points, sparkling and inconstant.
“(c) Luminous disks, with light generally fixed, and not sparkling.
“In one case the sea seemed on fire, and dolphins seemed to be fire.
“Again, the sea seemed to acquire an oily consistence, giving out soft homogeneous light, of a milky color, tinted with green or bluish. It is perhaps the least frequent, but most striking. It is due to the presence of noctiluca. It often resembled incandescent rain falling from the paddle-wheels of steamers.”
M. Giglioli agrees with Huxley in stating that “the phenomenon of phosphorescence in these animals does not reside in the protoplasmic branches, which, as is known, are sometimes wanting; but in the cortical substance it is not uniform, but manifests itself in distinct and very minute luminous points, which sparkle, go out, and light up again.”
[2] Page 9. Kiel observed this phenomenon in Peridinium. The following species of luminous forms existing in the Baltic Sea have been described by Ehrenberg: Prorocentrum micans, Peridinium michælis, Peridinium micans, Peridinium fuscus, Peridinium furca, Peridinium acuminatum, Lynchata baltica, and a species of Stentor.
[3] Page 9. Giglioli and his assistant, De Fillipi, observed luminosity in the gelatinous mass described by Hækel as Citophora.
The genera of those low forms most remarkable for luminosity are Thalassicolla, Collozoum, Sphærozoum, and Collosphæra. Giglioli states that the forms of this group which are found in the Indian Ocean and China seas are not luminous.
[4] Page 11. Dymophora fulgurans.
[5] Page 12. Other light-givers of this group are Willsea prolifera, Bourganivillia, and Lizzia.
[6] Page 12. Mueniopsis leidyii.
[7] Page 13. The Lucernaria is a very rare form of medusa on our northern shores, and particularly characteristic in color and form. It is more like a polyp in texture, and its rich beryl color distinguishes it from all other forms. It is related to the Discophores, animals belonging to one of the groups of jelly-fishes, or medusæ.
[8] Page 14. Schafer has observed radiating fibres on the under side, but there is no evidence to show that the luminosity originates here. In fact, the outer surface, where the cells of the delicate epithelium, or skin, contain minute points of fatty material, is equally phosphorescent. The tentacles become luminous, and it is supposed that they contain no nerves except at the margin of the disk. In some instances the light seems well defined at the so-called eye-spots at the edge of the disk, but its sudden fluctuations render any attempt at locating a photogenic structure difficult.
While numerous theories are advanced, investigators are entirely at fault as regards any satisfactory explanation of the phenomenon. There are certain conditions which are not favorable to the emission of light; and observers have seen medusæ, vividly luminous at one time, and not so at another.
It has been suggested that the light is subject to the so-called will of the creature. A better theory, perhaps, would attribute the luminosity to certain peculiar conditions, or to certain stages of existence.
[9] Page 15. Pleurobrachia rhodactyla, Agassiz. This is one of the numerous free-swimming marine animals, belonging to the Ctenophores. A group of the sea-jellies which have the pretty rows of paddles adown their long diameter. They are usually about a pigeon’s-egg in size, are oval, and in their element almost invisible, so colorless and transparent are they. A close inspection shows the paddles to be iridescent.
[10] Page 15. Idya roseola, Agassiz. Another form found near the shores of Nahant.
[11] Page 16. The Physophoridæ include the interesting forms, Physalia (Portuguese Man-of-War), Porpita, Vellela, etc. The first named indicates the character of the group, as its fleshy mass is surmounted by a beautiful bladder-like float, a mere bubble of membrane. These forms are not often seen out of tropical waters.
[12] Page 16. The term zooids is applied to the mass of tentacles and other fleshy parts of the Physophoræ. The long, extensile feelers are for prehension; others aid in locomotion, and some are reproductive; others are feeders for the entire colony. Thus it will be seen that these creatures are in a sense compound animals.
[13] Page 24. Alcyonarian corals from an order in the class Actinozoa.
[14] Page 24. Professor Moseley, of the “Challenger” expedition, was enabled to examine the light from these beautiful forms by the aid of the spectroscope, and found that it consisted of red, yellow, and green rays only.
[15] Page 25. Acanella normani Verril. A pretty soft coral, which has been dredged off the New-England coast by the fish-commission. This is a revelation to science, as no one was ready to believe that such forms, so common to the tropical regions, would be found where they were. The Gulf Stream runs so close to the North-eastern States, it will not, on reflection, seem strange that some creatures common to the warmer waters may find a home there.
[16] Page 25. Primnoa resida.
[17] Page 25. Paragorgia arborea.
[18] Page 26. Pennatulidæ. The name of a family of marine animals, which includes the Umbellularias, Veretillum, etc.,—the last highly phosphorescent.
[19] Page 26. While investigations so far have failed to explain the physiology of the light, it has been found that in a perfect animal it is emitted from eight opaque cords, each of which passes from a little swelling at the base of a tentacle down each polyp into the covering of the branch. The cords are canals in the sarcode of the branch, connecting the hollow of each tentacle with the tubular cavities of the branchlets and stem. The microscope shows that the contents of the canals are a fluid and cells; the latter containing minute highly refracting globular particles of a fatty substance, which resists decomposition long after the death of the polyp itself. If these cords are ruptured, the luminosity of the entire mass is excited, and the fatty cell contents is luminous after its escape, and on foreign matter even after the death of the animal.
Regarding the light, Duncan says, referring to Panceri’s experiments, “There is no sensible increase of temperature, and the tint of the monochromatic light is azure or greenish, but never red. In this beautiful instance of this remarkable vital luminousness there is evidently a photogenic structure and an elaborated organic material capable of producing light after removal from the animal. The sequence of illuminating the whole pen is slow,—far less than that of the movement of nerve-force. Yet the presence of the lowly organized nervous element indicates that the regulating of the light may relate to it as its function.”
Perhaps the most magnificent of all the Pennatulidæ is the tall Umbellularia grænlandica (Plate XXI., Fig. 2), which consists of twelve huge polyps, each with eight fringed arms, terminating in a close cluster upon a stalk about four feet in height. This striking form was dredged by the “Challenger” expedition in water over two miles in depth, where the pressure is so great one can hardly realize it, and the temperature is just above freezing. Sir Wyville Thompson says, that, when this splendid animal was taken from the trawl, it emitted a light so brilliant that Capt. Maclear found it an easy matter to determine the character of the light by the spectroscope. It gave a very restrictedly continuous spectrum, sharply included between the lines b and d.
[20] Page 27. Pavonia quadrangularis.
[21] Page 27. Asteronyx loveni.
[22] Page 27. Ophiacantha.
[23] Page 28. Renilla reniformis.
[24] Page 28. Virgularia is so named from its rod-like form; vira, a rod. V. mirabilis is found off the English coast.
[25] Page 30. Ophiura and Asterias. These are genera of the sea-stars, or star-fishes long so called; the former so named on account of the resemblance to snakes in its arms.
[26] Page 30. Ophiothrix fragilis, Amphiura belli, and Ophiocantha spinulosa.
[27] Page 31. Ophiocnida olivacea and Ophiocantha bidentata.
[28] Page 31. Brisinga elegans.
[29] Page 32. Astrophyton. There are several species of this star-fish, but each found in deep water. They are curiously circumscribed in locality. In one place off Cape Cod they are dredged, but in no other place, excepting farther south. Their name, basket-fish, is from their numerous intwined arms, resembling basket-work.
[30] Page 37. Serpula. A genus of the group Annelida.
[31] Page 37. Neiridæ and Eunicedæ. Genera of the group Annelida.
[32] Page 37. Polynoidæ, Scyllidæ, Chætopteridæ, and Polycirus.
[33] Page 38. Chætopterus norvegicus.
[34] Page 39. Harmothoe imbricata emits a bright greenish light when disturbed, the luminosity evidently proceeding from the point of attachment of each dorsal scale.
[35] Page 40. Pholas. A clam-like mollusk. Several species are found on Nahant beaches. P. dactylus is a European form. The genus Zirphæa is found from New England to Great Britain. All are more or less borers. A small species bores in hard mud on the Nahant beaches. Others are known to bore into hard wood and into stone.
Pholas dactylus will be seen to have photogenic or light-emitting structures and substances almost concealed in the tissues of the animal. The light-emitting portions are, according to Panceri, “two parallel cords containing an opaque white matter extending down the anterior siphon, two very small spots at its entrance, and finally an arched cord corresponding to the superior edge of the mantle, reaching to the middle near the valves. The white color of the cords, which stand out in relief, distinguishes them; and, although they are only elevations of the subcuticular tissue, they contain special cells, or rather epithelium, which produces the phosphorescent matter. The whole surface of the Pholas is covered with ciliated epithelium, which dips down into all the parts of the animal; but the special epithelium differs from this. It is nucleated and crammed with granules, and the cells are very refractive. The cells are very fragile, and allow their contents—i.e., granular nuclei and refractive granules—to escape readily. These are soluble in ether and alcohol. Under ordinary circumstances this photogenic apparatus is hidden; but violence readily displaces the special cells, which burst, and their contents are carried all over the surface by the water, assisted by the general ciliation. The white substance, fat-like, retains its luminosity, when spread out on paper, for hours; but the light does not appear to be accompanied by an evolution of heat. When it is placed in carbonic acid gas, the light pales and ceases. On the other hand, the photogenic substance, when barely luminous, is rendered so by physical contact. Agitation, and the addition of fresh or salt water, develop the light, and the same effect is produced by electricity and by heat. The light is monochromatic, and has a constant place in the spectrum as an azure band from E to F, that is to say, in the green.”
[36] Page 44. Dendronotus arborescens. A curiously decorated marine slug, found on the algæ of the waters around Massachusetts Bay. Eolis is another form nearly as interesting.
[37] Page 55. The spectrum of the light of comparatively few of these beetles has been examined. That of Photinus was found by Professor C. A. Young, the astronomer, to be continuous without lines, and to extend from Fraunhofer’s line C in the scarlet, to about F in the blue.
Mr. Meldola examined the spectrum of the light of the glow-worm some years ago, and found that it was continuous, being rich in blue and green rays, and comparatively poor in red and yellow.
[38] Page 56. Professor Carl Emery of the Entomological Society of Italy has kindly sent to us a detailed account of his experiments with the illuminating apparatus of a native luminous insect, the Luciola italica, etc. As these are the latest conclusions by the highest scientific authority, and therefore to be regarded as the most reliable, we here present a full account.
“The elytra of the insect Luciola were glued upon a holder of the microscope, and covered by a glass of tolerable thickness. On examining it, I got a favorable magnifying power, A of Zeiss. With stronger objective there is no good effect.
“The eye is at first dazzled by a strong, uniform yellowish light. But the intensity of this light is soon checked, the luminous field being interrupted by round spots. The light continues to diminish; the image becomes paler; and between the obscure round spots are seen to appear confused shadows, which detach themselves from the more brilliant rings. These rings are last to disappear when all the other portions have become dark. In the end they disappear entirely.
“The organ remains dark until the next flash; only here and there brilliant isolated points persist, which, as we shall see later, represent parenchymal cells which have retained their activity. If one places under the microscope the detached abdomen of a normal Luciola, and excites it by pressure of short duration by the cover glass, it is possible to obtain a flash which resembles the physiological flash.”
M. Emery states that he found it unsatisfactory to examine the insect while alive, as the constant movements rendered it nearly impossible to observe correctly the phenomenon of luminosity. He proceeds: “I have found by poisoning the Luciola by vapors of osmic acid an excellent method in fixing the light, and studying exactly the microscopic aspect.
“When one examines in a dark chamber the abdomen detached from a Luciola which has been plunged in a solution of osmic acid, it is seen that a part of the segments occupied by the luminous organs shine with a feeble and variable light; whilst another part (ordinarily in the neighborhood of the median line) is obscure, or as it were veiled by a light phosphorescent cloud. When the preparation is placed under the microscope, the luminous parts exhibit towards the top the appearance which we have already noted in examining normal Luciolas; that is to say, the existence of obscure round spots surrounded by brilliant field. In observing more attentively, one perceives around the spots other little spots, less obscure, and sometimes hardly visible, disposed with a certain degree of regularity.
“Now, if we compare these images with those which are presented under the microscope by the luminous organs when hardened in alcohol, and cleared up by caustic potash, or else a tangetized section made of the organ of an animal killed by osmic acid, and colored by carmine, it becomes evident that the large, obscure round spots correspond to the central part of the digitiform lobes of Targioni Tozzetti; that is to say, to the cylinders constituted by the matrix of trachea (Tracheenendzellen of M. Schultze), whilst the luminous part is represented by the parenchymentous cells, and the little obscure spots are due to nuclei of these same cells. Still towards the limit of the brilliant and obscure regions of the luminous organ a very varied spectacle is observed....
“From all the facts which we have just described, one may conclude with full certainty that the light of the Luciola has its seat in the parenchymentous cells of the luminous organ.”
“It remains to be seen if the luminous combustion does not also take place, though, with luminosity in other parts. In my previous work I had it that the surface of the cylindrical lobes formed by the matrix of the tracheæ was the principal focus or seat of the combustion. The facts which result from later observation oblige me to abandon this opinion....
“In the moments of mean luminous activity, one may say that the combustion is situated exclusively in the parenchymentous cells of the superficial layer of the luminous organ.”
[39] Page 73. Gammarus caudisetus, Gammarus longicornis, Gammarus truncatus, Gammarus heteroclitus, Gammarus crassimanus. Cyclops exiliens is also luminous.
[40] Page 77. Another species in which this change had taken place is Galathodes antonii, an allied form which is shown in the central figure of the frontispiece. Many more, as Willemœsea, Pentacheles, Polycheles, and others, have organs of vision, which have undergone more or less change. It has been suggested that certain deep-sea crabs, as Geryon tridens, Gonoplax, Donychus, and Munida, have phosphorescent eyes.
In Ptycogaster formosus (Plate XIII., Fig. 1), we find an interesting form, living at a depth of twenty-eight hundred and fifty feet, or more than half a mile, from the surface, which is provided with well-developed eyes.
[41] Page 81. The individual zooids, amounting to many hundreds, are grouped in whorls, their orifices so arranged that the inhalent are upon the outside of the cylinder, and the exhalent upon the interior. Each animal draws in a current from the outside, ejecting it into the interior; the result of this volume of water rushing from the open end being that the entire colony is forced along, at the same time revolving upon its long axis.
[42] Page 81. Panceri says, “Each zooid has two luminous spots, which are situated over the position of the ganglia of the nervous system; and there are loops like cords passing over the narrow end, connecting them.”
[43] Page 94. Dr. Gunther expressed the view that the organs are the producers, not the receivers, of light. He says, in brief, that the number of pairs of small globular bodies found along the abdominal profile is in direct relation to that of the vertebræ, the muscular system, etc. These are of two kinds. One class consists of the anterior, bi-convex, lens-like body, which is transparent during life; simple, or composed of rods, and coated with a dark membrane composed of hexagonal cells or rods arranged as in a retina. This structure characterizes the plates of _Stomias_ (Plate XX.), _Astronechtes_, _Chauliodus_ (Plate XXI., Fig. 4).
In the other set, as found in _Gonostoma_, _Myctoplum mausolicus_, and _Argyopelicus_, the organs have a simple, glandular structure. Branches of spinal nerves have been traced to each organ, and are distributed over the retina-like membrane of the glandular follicles.
The difference in structure of those organs naturally produces difference of opinion regarding their functions; but Gunther believes that all the organs in their functions have some relations to the conditions of light in which the fishes that possess them live. Three principal theories regarding them are given: first, they may all be accessory eyes; second, only the organs with the lenticular body are eyes, and those with glands are light-givers; third, all are producers of light. Many arguments have been advanced to support these different hypotheses; but it would seem that the second view is most tenable, from the fact that the organs with the retina-like membrane bear a great resemblance to a true eye, and finally the glandular organ in the little fish _Myctoplum_ has been seen to gleam with a phosphorescent light. Dr. Gunther thinks it not improbable that the compound organ is an accessory eye, and a light-producer as well. The light, he says, may be produced at the bottom of the posterior chamber, and emitted through the lenticular body in particular directions, with the same effect as when light is sent through the convex glass of a bull’s-eye.
[44] Page 104. Orthogoriscus mola.
[45] Page 128. Diatoms: Pyrocystis pseudo-noctiluca and P. fusciformis.
[46] Page 138. The common mushroom (Agaricus campestris), the meadow mushroom (Agaricus arvensis), the French champignon (Marasmius oreades), and in Austria Agaricus mellius, are eaten largely. Truffles (Tuber æstivum), Morels (Morchella esculenta), and Puff-ball (Lycoperdon giganteum) are also favorites in Europe.
[47] Page 138. Jew’s ear: Himcola auricula Judæ.
[48] Page 138. Myletta austratis.
[49] Page 149. See the description of ooze on page 3. This ooze is formed of the cast-off shells of the Diatoms, the minute vegetable forms of low organization.