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In this Plain Text version, Greek cursive characters used in formulae are
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[upsilon]. Symbols for male and female are represented as [male] and
[female]. In chemical formulae, the "left arrow over right arrow" symbol
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etc. The spellings of "Sidot blend" and "Sidot blende" are used
interchangeably in the text.
Some inconsistencies in formatting and punctuation have been retained
from the original. "PH" or P_{H} (P subscript H) is retained as used in
the text for the scale of alkali-acidity where the more familiar modern
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Changes to the text have been made only in the case of obvious spelling
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* * * * *
MONOGRAPHS ON EXPERIMENTAL BIOLOGY
EDITED BY
JACQUES LOEB, Rockefeller Institute
T. H. MORGAN, Columbia University
W. J. V. OSTERHOUT, Harvard University
THE NATURE OF ANIMAL LIGHT
BY
E. NEWTON HARVEY, Ph.D.
* * * * *
_MONOGRAPHS ON EXPERIMENTAL BIOLOGY_
PUBLISHED
FORCED MOVEMENTS, TROPISMS, AND ANIMAL CONDUCT
By JACQUES LOEB, Rockefeller Institute
THE ELEMENTARY NERVOUS SYSTEM
By G. H. PARKER, Harvard University
THE PHYSICAL BASIS OF HEREDITY
By T. H. MORGAN, Columbia University
INBREEDING AND OUTBREEDING: THEIR GENETIC AND SOCIOLOGICAL
SIGNIFICANCE
By E. M. EAST and D. F. JONES, Bussey Institution, Harvard
University
THE NATURE OF ANIMAL LIGHT
By E. N. HARVEY, Princeton University
IN PREPARATION
PURE LINE INHERITANCE
By H. S. JENNINGS, Johns Hopkins University
THE EXPERIMENTAL MODIFICATION OF THE PROCESS OF INHERITANCE
By R. PEARL, Johns Hopkins University
LOCALIZATION OF MORPHOGENETIC SUBSTANCES IN THE EGG
By E. G. CONKLIN, Princeton University
TISSUE CULTURE
By R. G. HARRISON, Yale University
PERMEABILITY AND ELECTRICAL CONDUCTIVITY OF LIVING TISSUE
By W. J. V. OSTERHOUT, Harvard University
THE EQUILIBRIUM BETWEEN ACIDS AND BASES IN ORGANISM AND ENVIRONMENT
By L. J. HENDERSON, Harvard University
CHEMICAL BASIS OF GROWTH
By T. B. ROBERTSON, University of Toronto
COORDINATION IN LOCOMOTION
By A. R. MOORE, Rutgers College
OTHERS WILL FOLLOW
* * * * *
Monographs on Experimental Biology
THE NATURE OF ANIMAL LIGHT
BY
E. NEWTON HARVEY, Ph.D.
PROFESSOR OF PHYSIOLOGY, PRINCETON UNIVERSITY
[Illustration]
PHILADELPHIA AND LONDON
J. B. LIPPINCOTT COMPANY
COPYRIGHT, 1920. BY J. B. LIPPINCOTT COMPANY
_Electrotyped and Printed by J. B. Lippincott Company.
The Washington Square Press, Philadelphia, U. S. A._
EDITORS' ANNOUNCEMENT
The rapid increase of specialization makes it impossible for one author
to cover satisfactorily the whole field of modern Biology. This
situation, which exists in all the sciences, has induced English authors
to issue series of monographs in Biochemistry, Physiology, and Physics.
A number of American biologists have decided to provide the same
opportunity for the study of Experimental Biology.
Biology, which not long ago was purely descriptive and speculative, has
begun to adopt the methods of the exact sciences, recognizing that for
permanent progress not only experiments are required but quantitative
experiments. It will be the purpose of this series of monographs to
emphasize and further as much as possible this development of Biology.
Experimental Biology and General Physiology are one and the same
science, in method as well as content, since both aim at explaining life
from the physico-chemical constitution of living matter. The series of
monographs on Experimental Biology will therefore include the field of
traditional General Physiology.
JACQUES LOEB,
T. H. MORGAN,
W. J. V. OSTERHOUT.
PREFACE
Bioluminescence, the production of light by animals and plants, has
always excited the admiration of the layman and the wonder of the
scientist. It is not surprising that an enormous literature dealing with
the subject has grown up. A large part of this literature, however, is
made up merely of reports that a certain animal is luminous, or records
of especially brilliant phosphorescence of the sea. Among those who have
inquired somewhat more carefully into the nature and causes of light
production may be mentioned the names of Beijerinck, R. Boyle, Dahlgren,
Dubois, Ehrenberg, Krukenberg, Mangold, McDermott, Molisch, Panceri,
Pflueger, Phipson, Quatrefages, Spallanzani, and Trojan. Several of these
men have written comprehensive monographs on the subject.
It is not the purpose of this book to deal with every phase of
bioluminescence. Volumes could be written on the evolutionary side of
the problem and the structure and uses of luminous organs. These
questions can only be touched upon. Neither is it my purpose to discuss
the ultimate cause of the light, whether due to vibration of electrons
or to other causes. That problem must be left to the physicist, although
it is highly probable that a study of animal light will give important
information regarding the nature of light in general, and no theory of
light can be adequate which fails to take into account the extraordinary
powers of luminous animals.
We shall be concerned largely with the physical characteristics of
animal light and the chemical processes underlying its production.
Great advances have been made since the first early guesses that the
light was due to phosphorus and was a kind of oxidation. Although the
problem cannot be considered as solved, it has been placed on a sound
physico-chemical basis. Some material is oxidized. Exactly what this
material is and why light accompanies its oxidation are the two more
fundamental problems in the field of Bioluminescence. How far and with
what success we have progressed toward a solution of these problems may
be seen from a perusal of the following pages.
It gives me pleasure to acknowledge the kindness of Dr. W. E. Forsythe
of the Nela Institute, Cleveland, Ohio, in reading and criticizing the
manuscript of Chapter III, and of Professor Lyman of Harvard University
for a similar review of Chapter II. I am also deeply indebted to my wife
for reading the proof and to Dr. Jacques Loeb and Prof. W. J. V.
Osterhout for many suggestions throughout the book. My thanks are also
due to Prof. C. Ishikawa of the Agricultural College, Imperial
University of Tokio, Japan, for his generous assistance in providing
_Cypridina_ material. Finally I wish to acknowledge the support of the
Carnegie Institution of Washington, through its director of Marine
Biology, Dr. Alfred G. Mayor. Without this support much of the work
described in this book could not have been accomplished.
E. N. H.
PRINCETON, N. J.,
October, 1919.
CONTENTS
CHAPTER PAGE
I. LIGHT-PRODUCING ORGANISMS 1
Early records and theories. "Shining fish and flesh." "Burning
of the sea." Distribution of luminous organisms in plant
and animal kingdoms. Secondary luminosity. False luminosity.
St. Elmo's fire. Ignis fatuus. Flashing of flowers.
Luminosity in man. Use to man of photogenic organisms.
II. LUMINESCENCE AND INCANDESCENCE 20
The complete spectrum. Radiation and temperature. "Cold
light." Thermoluminescence. Phosphorescence and fluorescence.
Triboluminescence and piezoluminescence. Crystalloluminescence.
Chemiluminescence.
III. PHYSICAL NATURE OF ANIMAL LIGHT 40
Purkinje phenomenon. Color and spectra of animal light.
Polarization. Efficiency of animal light. Infra-red radiation.
Ultra-violet radiation. Luminous efficiency and visual sensibility.
Production of radiation penetrating opaque objects.
Intensity of animal light. Summary.
IV. STRUCTURE OF LUMINOUS ORGANS 67
Photochemical and chemiphotic changes. The eye and the
luminous organ. Intracellular and extracellular luminescence.
Continuous and intermittent luminescence. Periodicity of
luminescence. Luminous bacteria. _Noctiluca_ and photogenic
granules. _Chaetopterus_ and luminous gland cells. _Cypridina._
Luminous glands. The firefly. Luminous organs (photophores)
with lenses, reflectors, opaque and color screens. Uses and
purpose of animal light.
V. THE CHEMISTRY OF LIGHT PRODUCTION, PART I 85
Boyle's and Spallanzani's experiments. Shining wood and burning
coal. Oxygen and luminescence. Carbon dioxide and
luminescence. Heat production during luminescence. Luminescence
and respiration. Water and luminescence. Phipson's
noctilucin. Luciferin and luciferase. Photogenin and photophelein.
Proluciferin. Oxyluciferin. Pyrophorin or luciferescein.
Chemiluminescent reactions. "Biozymooxyluminescence."
VI. THE CHEMISTRY OF LIGHT PRODUCTION, PART II 114
_Pyrophorus_ luciferin and luciferase. _Pholas_ luciferin and
luciferase. _Cypridina_ luciferin; stability, hydrolysis by acid
and enzymes, adsorption, precipitation, salting out, solubility,
distribution. _Cypridina_ luciferin a proteose? _Cypridina_
luciferase and properties. _Cypridina_ luciferase an albumin.
Specificity of luciferase. Action of fat solvent anaesthetics.
Action of cyanides. Oxyluciferin. Nature of oxidative reaction.
VII. DYNAMICS OF LUMINESCENCE 143
Minute amounts of material for luminescence. Reaction velocity
and chemiluminescence. Temperature and chemiluminescence.
Oxidation in steps. Concentration and bioluminescence. Temperature
and bioluminescence. Oxidation with and without
luciferase. Reaction velocity and color of bioluminescence.
* * * * *
THE NATURE OF ANIMAL LIGHT
CHAPTER I
LIGHT-PRODUCING ORGANISMS
The fact that animals can produce light must have been recognized from
the earliest times in countries where fireflies and glowworms abound,
but it is only since the perfection of the microscope that the
phosphorescence of the sea, the light of damp wood and of dead fish and
flesh has been proved to be due to living organisms. Aristotle mentions
the light of dead fish and flesh and both Aristotle and Pliny that of
damp wood. Robert Boyle in 1667 made many experiments to show that the
light from all three sources, as well as that of the glowworm, is
dependent upon a plentiful supply of air and drew an interesting
comparison between the light of shining wood and that of a glowing coal.
Boyle had no means of finding out the true cause of the light and early
views of its nature were indeed fantastic. Even as late as 1800 Hulme
concludes from his experiments on phosphorescent fish that the light is
a "constituent principle of marine fishes" and the "first that escapes
after the death of the fish." It was only in 1830 that Michaelis
suspected the light of dead fish to be the result of some living thing
and in 1854 Heller gave the name _Sarcina noctiluca_ to the suspected
organism. In 1875 Pflueger showed that nutrient media could be inoculated
with small amounts of luminous fish and that these would increase in
size, like bacterial colonies, and we now know that the light of all
dead fish and flesh is due to luminous bacteria.
In the early part of the nineteenth century it was surmised that the
light of damp wood was connected with fungus growth because of a
similarity in smell. In 1854 Heller recognized minute strands, which he
called _Rhizomorpha noctiluca_, as the actual source of the light. We
now know that all phosphorescent wood is due to the mycelium of various
kinds of fungi and that sometimes the fruiting body of the fungus also
produces light.
The phosphorescence or "burning of the sea," which is described by so
many of the older explorers, is also due entirely to living organisms,
both microscopic and macroscopic. The latter are mostly jelly-fish
(_medusae_) or comb jellies (_Ctenophores_) and give rise to the larger,
more brilliant flashes of light often seen in the wake or about the
sides of a steamer at night. The former are various species of
dinoflagellates or cystoflagellates such as _Noctiluca_ (just visible to
the naked eye) which collect at the surface of the sea and often
increase in such numbers that the water is colored by day (usually pink
or red) and shines like a sheet of fire when disturbed at night.
Although _Noctiluca_ was recognized as a luminous animal in 1753 by
Baker, the light of the sea was a mysterious phenomenon to the older
observers. MacCartney, speaking before the Royal Society in 1810,
outlines the various older theories as follows: "Many writers have
ascribed the light of the sea to other causes than luminous animals.
Martin supposed it to be occasioned by putrefaction; Silberschlag
believed it to be phosphoric; Prof. J. Mayer conjectured that the
surface of the sea imbibed light, which it afterwards discharged. Bajon
and Gentil thought the light of the sea was electric, because it was
excited by friction.... I shall not trespass on the time of the Society
to refute the above speculations; their authors have left them
unsupported by either arguments or experiments, and they are
inconsistent with all ascertained facts upon the subject. The remarkable
property of emitting light during life is only met amongst animals of
the four last classes of modern naturalists, viz., mollusca, insects,
worms, and zoophytes." MacCartney recognized the true cause of the
light, although he had little idea of the vast number of marine forms
which are luminous and omits entirely any reference to the fishes, many
of which produce a light of their own when living, apart from any
bacterial infection.
A survey of the animal kingdom discloses at least 36 orders containing
one or more forms known to produce light and several more orders
containing species whose luminosity is doubtful. In the plant kingdom
there are two groups containing luminous forms. The distribution of
luminous organisms is brought out in the accompanying classification of
plants and animals. Those orders are printed in italics which contain
species whose self-luminosity is fairly well established. It will be
noted that further subdivisions into orders is not given in classes of
animals which lack luminous forms.
TABLE I
_DISTRIBUTION OF LUMINOUS ORGANISMS IN PLANT AND ANIMAL KINGDOMS_
PLANT KINGDOM
I. _Thallophyta_
Algae
Cyanophyceae (Blue-green Algae)
Chlorophyceae (Green Algae)
Phaeophyceae (Brown Algae)
Rhodophyceae (Red Algae)
Lichenes (Lichens, symbiotic growth of algae and fungi)
_Fungi_
Myxomycetes (Slime moulds)
_Schizomycetes_ (Bacteria)
_Bacterium_, _Photobacterium_, _Bacillus_, Pseudomonas_,
_Micrococcus_, _Microspira_, _Vibrio_.
Phycomycetes (moulds)
Ascomycetes (Sac fungi, yeasts, some moulds)
_Basidiomycetes_ (Smuts, rusts, mushrooms)
Ustilaginae (Smuts)
Uridineae
Auriculariae (Judas ears)
Tremellineae (Jelly fungi)
_Hymenomycetes_ (Mushrooms)
_Agaricus_, _Armillaria_, _Pleurotus_, _Panus_, _Mycena_,
_Omphalia_,
_Locellina_, _Marasinium_, _Clitocybe_, _Corticium_.
Gasteromycetes (Stinkhorns and puff-balls)
II. Bryophyta
Hepaticae (Liverworts)
Musci (Mosses)
III. Pteridophyta
Equisetineae (Horsetails)
Salviniae (Salvinia, Marsilia, etc.)
Lycopodineae (Club Mosses)
Filicineae (Ferns)
IV. Spermatophyta
Gymnospermae (Cycads, Ginkgo, Conifers)
Angiospermae (Mono- and Dicotyledonous flowering plants).
ANIMAL KINGDOM
I. _Protozoa._ (One-celled animals)
_Sarcodina_
Rhizopoda
Heliozoa
_Radiolaria_
_Thallassicola_, _Myxosphaera_, _Collosphaera_, _Collozoum_,
_Sphaerozoum_.
_Mastigophora_
Flagellata
Choanoflagellata
_Dinoflagellata_
_Ceratium_, _Peridinium_, _Prorocentrum_, _Pyrodinium_,
_Gonyaulax_, _Blepharocysta_, _Amphidinium_, _Diplopsalis_,
_Cochlodinium_, _Sphaerodinium_, _Gymnodinium._
_Cystoflagellata_
_Noctiluca_, _Pyrocystis_, _Leptodiscus_, _Craspedotella._
Sporozoa
Infusoria
II. Porifera (Sponges)
Calcarea
Hexactinellida
Desmospongiae
III. _C[oe]lenterata_
_Hydrozoa_ (Hydroids and Jelly-fish)
_Leptomedusae_ or _Campanulariae_
Medusa form--_Eutima_, _Phyalidium_ (_Oceania_).
Hydroid form--_Aglaophenia_, _Campanularia_, _Sertularia_,
_Plumularia_,
_Cellularia_, _Valkeria_, _Obelia_, _Clytia_.
_Trachomedusae_
_Geryonia_, _Lyriope_, _Aglaura_
_Narcomedusae_
_Cunina_
_Anthomedusae_ or _Tubulariae_
Medusa form--_Thaumantias_, _Tiara_, _Turris_, _Sarsia_.
Hydroid form--?
Hydrocorallinae
_Siphonophora_
_Abyla_, _Praya_, _Diphyes_, _Eudoxia_, _Hippopodius._
_Scyphozoa_ (Jelly-fish)
Stauromedusae
Peromedusae
_Cubomedusae_
_Carybdia_
_Discomedusae_
_Pelagia_, _Aurelia_, _Chrysaora_, _Rhizostoma_, _Cyanaea_,
_Dianea_, _Mesonema_.
_Actinozoa_ (Corals, Sea-fans, Sea-pens, Sea-anemones)
Actinaria
Madreporareia
Antipatharia
_Alcyonaria_
_Alcyonium_, _Gorgonia_, _Isis_, _Mopsea_
_Pennatulacea_
_Pennatula_, _Pteroides_, _Veretillum_, _Cavernularia._
_Funicularia_, _Renilla_, _Pavonaria_, _Stylobelemon_,
_Umbellularia_, _Virgularia?_
_Ctenophora_ (Comb-jellies)
_Cydippida_
_Pleurobranchia_.
_Lobata_
_Mnemiopsis_, _Bolinopsis_, _Leucothea_ (_Eucharis_).
_Cestida_
_Cestus_.
_Beroida_
_Beroe._
IV. Platyhelminthes
Turbellaria (Flat-worms)
Trematodes (Parasitic flat-worms)
Cestodes (Tape-worms)
Nemertinea (Nemertines)
V. Nemathelminthes
Nematoda (Round worms)
Gordiacea (Hair worms)
Acanthocephala (Acanthocephalids)
Chaetognatha (Sagitta)
VI. Trochelminthes
Rotifera (Wheel animalcules)
Gastrotricha (Chaetonotus)
Kinorhyncha (Echinoderes)
VII. _Molluscoidea_
_Bryozoa_ (Corallines)
Entoprocta
_Ectoprocta_
_Membranipora_, _Scrupocellaria_, _Retepora?_ _Flustra?_
Brachiopoda (Lamp shells)
Phoronidea (Phoronis)
VIII. _Annulata_
Archiannelida (Primitive worms, including Dinophilus)
_Chaetopoda_ (True worms)
_Polychaeta_
_Chaetopterus_, _Phyllochaetopterus_, _Telepsaris_, _Polynoe_,
_Acholoe_, _Tomopteris_, _Odontosyllis_, _Lepidonotus_,
_Pionosyllis_, _Phyllodoce_, _Heterocirrus_, _Polyopthalamus?_
_Oligochaeta_
_Lumbricus_, _Photodrilus_, _Allolobophora_ (_Eisemia_),
_Microscolex_, _Nonlea_, _Enchytraeus_, _Octochaetus_.
Gephyrea (Sipunculus)
Hirudinea (Leeches)
Myzostomida (Myzostomus)
IX. _Echinodermata_
Asteroidea (Star-fish)
_Ophiuroidea_ (Brittle-stars)
_Ophiurida_
_Ophiopsila_, _Amphiura_, _Ophiacantha_, _Ophiothrix_,
_Ophionereis_.
Euryalida
Echinoidea (Sea urchins)
Holothuroidea (Sea Cucumbers)
Crinoidea (Feather-stars)
X. _Arthropoda_
_Crustacea_ (Crabs, lobsters, shrimps, etc.)
Phyllapoda
_Ostracoda_
_Halocypris_, _Cypridina_, _Pyrocypris_, _Conch[oe]cia_,
_Cyclopina_.
_Copepoda_
_Metridia_, _Leuckartia_, _Pleuromma_, _Oncaea_, _Heterochaeta_.
Cirripedia
Phyllocardia
_Schizopoda_
_Nyctiphanes_, _Nematoscelis_, _Gnathophausia_, _Euphausia_,
_Stylochiron_, _Boreophausia_, _Mysis?_
_Decapoda_
_Sergestes_, _Aristeus_, _Heterocarpus_, _Hoplophorus_,
_Acanthephyra_, _Pentacheles_, _Colossendeis_
Stomatopoda
Cumacea
Amphipoda
Isopoda
Onychophora (Peripatus)
_Myriapoda_ (Centipedes and Millepedes)
Symphyla
_Chilopoda_
_Geophilus_, _Scolioplanes_, _Orya_.
Diplopoda
Pauropoda
_Insecta_ (Insects)
_Aptera_ (Spring-tails)
_Lipura_, _Amphorura_, _Neanura_
Orthoptera
_Neuroptera_
_Teleganoides and Caenis_ of the Mayflies? _Termites?_
Hemiptera
_Diptera_ (Flies)
_Bolitophila_ and _Ceroplatus_ larvae, _Thyreophora?_
_Coleoptera_ (Beetles)
_Pyrophorus_, _Photophorus_, _Luciola_, _Lampyris_, _Phengodes_,
_Photuris_, _Photinus_, etc.
Lepidoptera
Hymenoptera
Arachnida (Spiders)
XI. _Mollusca_
Amphineura (Chiton)
_Pelecypoda_ (Bivalves)
Protobranchia
Filibranchia
Pseudo-Lamellibranchia
_Eu-lamellibranchia_
_Pholas_
Septibranchiata
_Gasteropoda_ (Snails, periwinkles, slugs, etc.)
Prosobranchiata
_Ophisthobranchiata_
_Phyllirrhoe_, _Plocamopherus_.
Pulmonata
Scaphopoda (Dentalium)
_Cephalopoda_ (Squids and Octopus)
Tetrabranchiata
_Dibranchiata decapoda_
_Onychoteuthis_, _Chaunoteuthis_, _Lycoteuthis_, _Nematolampas_,
_Lampadioteuthis_, _Enoploteuthis_, _Abralia_, _Abraliopsis_,
_Watasenia_, _Ancistrocheirus_, _Thelidioteuthis_,
_Pterygioteuthis_, _Pyroteuthis_, _Octopodoteuthis?_,
_Calliteuthis_, _Histioteuthis_, _Benthoteuthis_,
_Hyaloteuthis_, _Eucleoteuthis_, _Chiroteuthis_,
_Mastigoteuthis_, _Cranchia_, _Liocranchia_, _Pyrgopsis_,
_Leachia_, _Liguriella_, _Phasmatopsis_, _Toxeuma_,
_Megalocranchia_, _Leucocranchia_, _Crystalloteuthis_,
_Phasmatoteuthis_, _Galiteuthis_, _Corynomma_,
_Hensenioteuthis_, _Bathothauma_, _Rossia?_, _Heteroteuthis_,
_Iridoteuthis_, _Sepiola_, _Rondeletia_, _Inioteuthis_,
_Euprymna_, _Melanoteuthis?_.
XII. _Chordata_
_Adelochorda_ (Balanoglossus)
_Balanoglossus_, _Ptychodera_, _Glossobalanus_
_Urochorda_ (Ascidians)
_Larvacea_
_Appendicularia?_
_Thaliacea_
_Salpa_, _Doliolum?_
_Ascidiacea_
_Pyrosoma_, _Phallusia_
Acrania (Amphioxus)
Cyclostomata (Cylostomes)
_Pisces_ (Fishes)
_Elasmobranchii_
_Centroscyllium_, _Spinax_, _Paracentroscyllium_, _Isistius_,
_Laemargus_, _Euproctomicrus_, _Benthobatis?_
Holocephalii
Dipnoi
_Teleostomi_
_Stomias_, _Chauliodus_, _Melanostomius_, _Pachystomias_,
_Bathophilus_, _Dactylostomius_, _Malacosteus_, _Astronesthes_,
_Ophozstomias_, _Idiacanthus_, _Bathylychnus_, _Macrostomius_,
_Gonostoma_, _Cyclothone_, _Photichthys_, _Vinciguerria_,
_Ichthyococcus_, _Lychnopoles_, _Diplophos_, _Triplophos_,
_Valenciennellus_, _Maurolicus_, _Argyropelecus_, _Sternoptyx_,
_Polyipnus_, _Ipnops? Neoscopelus_, _Myctophum_, _Halosausus_,
_Xenodermichthys? Macrurus? Photoblepharon_, _Anomalops_,
_Porichthys_, _Leuciocornus_, _Mixonus? Bassozetus? Oneirodes_,
_Ceratias_, _Gigantactis_, _Chaunax_, _Malthopsis_,
_Halicmetus_, _Monocentris_, _Lamprogrammus._
Amphibia (Frogs, Toads, Salamanders)
Reptilia (Snakes, Lizards, Turtles)
Aves (Birds)
Mammalia (Mammals)
The only groups of the plant kingdom which are known to produce light
are some of the bacteria and some of the fungi and the dinoflagellates
(_Peridineae_) if one is to include them among the plants. Many different
species of phosphorescent bacteria have been described, differing in
cultural characteristics and structural peculiarities and grouped in the
genera, _Bacterium_, _Photobacterium_, _Bacillus_, _Microspira_,
_Pseudomonas_, _Micrococcus_, and _Vibrio_. Specific names indicating
their light-producing power such as _phosphorescens_, _phosphoreum_,
_luminosum_, _lucifera_, etc., have been applied.
All the fungi which are definitely known to produce light belong to the
_Basidiomycetes_, the largest and most highly developed of the true
fungi. Either the mycelium alone or the fruiting body alone, or both,
may be luminescent.
Among animals the best known forms are the dinoflagellates; _Noctiluca_;
hydroids; jelly-fish; ctenophores; sea pens; _Chaetopterus_ and other
marine worms; earthworms; brittle stars; various crustaceans; myriapods;
fireflies and glowworms, the larvae of fireflies; _Pholas dactylus_ and
_Phyllirrhoe bucephala_, both molluscs; squid; _Pyrosoma_, a colonial
ascidian; and fishes.
Luminous animals are all either marine or terrestrial forms. No examples
of fresh water luminous organisms are known. Of marine forms, the great
majority are deep sea animals, and it is among these that the
development of true luminous organs of a complicated nature is most
pronounced. Many of the luminous marine animals are to be found in the
plankton, while the littoral luminous forms are in the minority. Some
members of all the above groups are found at one or another of our
marine laboratories with the possible exception of _Pholas_,
_Phyllirrhoe_ and squid. Although earthworms and myriapods which produce
light are found in the United States, they are rather rare and seldom
observed forms.
Not only adult forms but the embryos and even the eggs of some animals
are luminous. The egg of _Lampyris_ emits light within the ovary and
freshly laid eggs are quite luminous. The light does not come from
luminous material of the luminous organ adhering to the egg when it is
laid but from within the egg itself. _Pyrophorus_ eggs are also
luminous. The segmentation stages of _Ctenophores_ are luminous on
stimulation, as noted by Allman (1862), Agassiz (1874) and Peters
(1905), but the eggs themselves do not luminesce. _Schizopod larvae_
(Trojan, 1907), _Copepod nauplii_ (Giesbrecht, 1895), _Chaetopterus
larvae_ (Enders, 1909), and brittle star _plutei_ (Mangold, 1907) also
produce light.
Apparently there is no rhyme or reason in the distribution of
luminescence throughout the plant or animal kingdom. It is as if the
various groups had been written on a blackboard and a handful of sand
cast over the names. Where each grain of sand strikes, a luminous
species appears. The _C[oe]lenterates_ have received most sand.
Luminescence is more widespread in this phylum and more characteristic
of the group as a whole than any other. Among the arthropods luminous
forms crop up here and there in widely unrelated groups. In the
mollusks, excluding the cephalopods, only two luminous species are
known. Several _phyla_ contain no luminous forms whatever. It is an
extraordinary fact that one species in a genus may be luminous and
another closely allied species contain no trace of luminosity. There
seems to have been no development of luminosity along direct
evolutionary lines, although a more or less definite series of
gradations with increasing structural complexity may be traced out among
the forms with highly developed luminous organs.
While the accompanying list of luminous genera aims to be fairly
complete, there are no doubt omissions and some inaccuracies in it.
Anyone who has ever tried to determine what animal is responsible for
the occasional flashes of light observed on agitating almost any sample
of sea water will realize how difficult it is to discover the luminous
form among a host of non-luminous ones, especially if the animal is
microscopic in size. It is not surprising, then, to find many false
reports of luminous animals in the literature of the subject and we
cannot be too careful in accepting as luminous a reported case. The
difficulty lies chiefly in the fact that all luminous organisms with the
exception of bacteria, fungi, and a few fish, flash only on stimulation,
and, while it is easy enough to see the flash, the animal is lost
between the flashes. The only safe way to detect luminous organisms is
to add a little ammonia to the sea water. This slowly kills the
organisms and causes any luminous forms to glow with a steady,
continuous light for some time, a condition accompanying the death of
the animal. Not all observers, however, have followed this method. One
must always be on guard against confusing the light from a supposed
luminous form with the light from truly luminous organisms living upon
it. The reported cases of luminosity among marine algae are now known to
be due to hydroids or unicellular organisms living on the alga.
We know also that many non-luminous forms may become infected with
luminous bacteria, not only after death, but also while living, so that
their luminescence is purely secondary. Giard and Billet (1889-90)
succeeded in inoculating many different kinds of amphipod crustacea
(_Talitrus_, _Orchestia_, _Ligia_) and isopod crustacea (_Porcellio_,
_Philoscia_) with luminous bacteria, in some cases passing the infection
from one to the next through nine individuals. Curiously enough the
bacterium did not produce light on artificial culture media but did when
growing in the body of the crustacea, which were killed in about seven
days by the infection. The species of _Talitrus_ and _Orchestia_ might
easily have been taken for truly luminous animals if not carefully
investigated.
Tarchanoff (1901) has injected luminous bacteria into the dorsal lymph
sac of frogs with the result that the animals continued to glow for
three to four days, especially about the tongue. I remember once while
collecting luminous beetles in Cuba, I was astounded to find a frog
which was luminous. Expecting this animal to be of great interest, I
examined it further only to find that the frog had just finished a
hearty meal of fireflies, whose light was shining through the belly with
considerable intensity.
Infection with luminous bacteria is especially liable to occur in any
dead marine animal. The flesh is an excellent culture medium. I have
seen non-luminous species of squid, recently killed, covered with minute
growing colonies, quite evenly spaced, so as to closely resemble
luminous species whose light is restricted to scattered light organs
over the surface of the body.
Indeed Pierantoni (1918) has carried this idea to extremes. He believes
that in the luminous organs of fireflies, cephalopods and _Pyrosoma_,
luminous symbiotic bacteria occur which are responsible for the light
of these animals, and he claims in the case of cephalopods and
_Pyrosoma_ to have been able to isolate these in pure culture on
artificial culture media. In the firefly they can be seen but not grown
and in luminous animals where no visible bacteria-like structures are
apparent he believes we are dealing with ultra-microscopic luminous
bacteria similar to the pathogenic forms suspected in filterable
viruses. While the assumption of ultra-microscopic organisms makes the
refutation of Pierantoni's views a somewhat hazardous task, no one can
deny that even an ultra-microscopic organism will be killed by boiling
with 20 per cent. (by wt.) HCl for 6 hours. As we shall see, the
luminous material of _Cypridina_, an ostracod crustacean, can withstand
such prolonged boiling with strong acid. The light of one animal at
least, and I believe many others also, cannot be due to any sort of
symbiotic organism.
Apart from these cases where light is actually produced but is not
primary, not produced by the animal itself, there are many forms whose
surface is so constituted as to produce interference colors. This is
true in many cases among the birds and butterflies whose feathers and
scales are iridescent. Some of these have been erroneously described as
luminous. Perhaps the best known case among aquatic animals is
_Sapphirina_, a marine copepod living at the surface of the sea, and
especially likely to be collected with other luminous forms. Its cuticle
is so ruled with fine lines as to diffract the light and flash on moving
much as a fire opal. Needless to say no trace of light is given off from
this animal in a totally dark room.
It has often been supposed that the eye of a cat or of other animals is
luminous. The eyes of a moth, also, can be seen to glow like beads of
fire when it is flying about a flame. Both of these cases are, however,
purely reflection phenomena and due to reflection out of the eye again
of light which has entered from some external source. The correct
explanation was given by Prevost in 1810. The eye of any animal is quite
invisible in absolute darkness. The same explanation applies to the
moss, _Schistostega_, which lives in dimly illuminated places and whose
cells are almost spherical, constructed like a lens, so as to refract
the light and condense it on the chloroplasts at the bottom of the
cells. Some of this light is reflected out of the cells again and gives
the appearance of self-luminosity. The alga, _Chromophyton rosanoffii_,
is another example of apparent luminosity, due to reflection from almost
spherical cells.
There are several light phenomena known which have nothing to do with
living organisms. Commonest of these is St. Elmo's fire ("corposants" of
English sailors), a glow accompanying a slow brush discharge of
electricity, which appears as a tip of light on masts of ships, spires
of churches or even the fingers of the hand. It is best seen in winter
during and after snowstorms and is a purely electrical phenomenon.
Less well known is the _Ignis fatuus_ (Will-o'-the-Wisp,
Jack-o'-Lantern, spunkie), a fire seen over marshes and stagnant pools,
appearing as a pale bluish flame which may be fixed or move, steady or
intermittent. So uncommon is this phenomenon that its nature is not well
understood, but it is believed to be the result of burning _phosphine_
(PH_{3} + P_{2}H_{4}), a self-inflammable gas, generated in some way
from the decomposition of organic matter in the swamp. The difficulty
with this explanation is that phosphine is not known as a decomposition
product of organized matter. Methane (CH_{4}), a well-known
decomposition product of organic matter and abundantly formed in swamps,
will burn with a pale bluish flame and some have thought the _Ignis
fatuus_ to be the result of this gas. As methane is not self-inflammable
there remains the difficulty of explaining how it becomes lighted.
Although still a mystery, it is possible that this light is also of
electrical origin or that in some cases large clusters of luminous fungi
have been observed.
The flashing of flowers, especially those of a red or orange color, like
the poppy, which many observers have noticed during twilight hours, is a
purely subjective phenomenon due to the formation of after images in
eyes partially adapted to the dark. This flashing, first observed by the
daughter of Linnaeus, is never observed in total darkness or in the
direct field of vision, but only in the indirect field as during a
sidelong glance at the plant.
There are some cases of luminosity on record in connection with man
himself. (See Heller, 1854). Before the days of aseptic and antiseptic
surgery, wounds frequently became infected with luminous bacteria and
glowed at night. The older surgeons even supposed that luminous wounds
were more apt to heal properly than non-luminous ones. We know that
luminous bacteria are non-pathogenic, harmless organisms and the
presence of these forms even on dead fish or flesh never accompanies but
always precedes putrefaction. As recorded by Robert Boyle, no harm has
come from eating luminous meat, unless it may also have become infected
with pathogenic forms.
A few cases of luminous individuals have been noted in which the skin
was the source of light, especially if the person sweated freely. It is
possible that here we are again dealing with luminous bacteria upon the
accumulations of substances passed out in the sweat, which serves as a
nutrient medium.
There are also on record, in the older literature, cases of luminous
urine, where the urine when freshly voided was luminous. If these
observations are correct and they may, perhaps, be doubted, we are at
present uncertain of the cause of the light. Bacterial infections of the
bladder are not inconceivable although luminous bacteria are strongly
aerobic and would not thrive under anaerobic conditions. I can state
from my own experiments that luminous bacteria will live in normal human
urine, but not well. In albuminous urines it is very likely that they
would live better, and it is possible that the luminous urines reported
are the results of luminous bacterial infection. On the other hand, the
light may be purely chemical, due to the oxidation of some compound, an
abnormal incompletely oxidized product of metabolism, which oxidizes
spontaneously in the air. We know that sometimes these errors in
metabolism occur, as in _alkaptonuria_, where homogentistic acid is
excreted in the urine and on contact with the air quickly oxidizes to a
dark brown substance. Light, however, has never been reported to
accompany the oxidation of homogentistic acid, although it does
accompany the oxidation of some other organic compounds. (See Chapter
II.)
Finally, we may inquire to what extent luminous animals may be utilized
by man. Leaving out of account the use of tropical fireflies for
adornment by the natives of the West Indies and South America and the
use for bait, in fishing, of the luminous organ of a fish,
_Photoblepharon_, by the Banda islanders, we find that luminous bacteria
are of value for certain purposes in the laboratory.
These methods are all due to Beijerinck (1889, 1902). He has, for
instance, used luminous bacteria for testing bacterial filters. If there
is a crack in the filter the bacteria will pass through and a luminous
filtrate is the result, but a perfect filter allows no organisms to pass
and gives a dark filtrate.
Luminous bacteria are also very sensitive to oxygen and cease to
luminesce in its absence. By mixing luminous bacteria with an emulsion
of chloroplasts (from clover leaves) in the dark, allowing the bacteria
to use up all the oxygen, and then exposing the mixture to light of
various colors, the effect of different wave-lengths in causing
photosynthesis could be studied. Only if the chloroplasts are exposed to
a color in the spectrum which decomposes CO_{2} with liberation of
oxygen do the bacteria luminesce, and when this oxygen is used up by the
bacteria, the tube again becomes dark. Beijerinck has also worked out a
method of testing for maltose and diastase with luminous bacteria, based
on the fact that a certain form, _Photobacterium phosphorescens_, will
only produce light in presence of maltose or diastase which will form
maltose from starch.
Although Dubois and Molisch have both prepared "bacterial lamps" and
although it has been suggested that this method of illumination might be
of value in powder magazines where any sort of flame is too dangerous,
it seems doubtful, to say the least, whether luminous bacteria can ever
be used for illumination. Other forms, perhaps, might be utilized, but
bacteria produce too weak a light for any practical purposes. The
history of Science teaches that it is well never to say that anything is
impossible. It is very unlikely that any luminous animal can be utilized
for practical illumination, but there is no reason why we cannot learn
the method of the firefly. Then we may, perhaps, go one step further and
develop a really efficient light along similar lines. To what extent our
inquiry into the "secret of the firefly" has been successful may be
gleaned from the following pages.