GUIDE TO THE STUDY OF FISHES
[Illustration]
[Illustration]
A GUIDE
TO
THE STUDY OF FISHES
BY
DAVID STARR JORDAN
_President of Leland Stanford Junior University_
_With Colored Frontispieces and 427 Illustrations_
IN TWO VOLUMES
VOL I.
"I am the wiser in respect to
all knowledge and the better
qualified for all fortunes for
knowing that there is a minnow in
that brook."--_Thoreau_
[Illustration]
NEW YORK
HENRY HOLT AND COMPANY
1905
Copyright, 1905
BY
HENRY HOLT AND COMPANY
Published March, 1905
To
Theodore Gill,
Ichthyologist, Philosopher, Critic, Master in Taxonomy,
this volume is dedicated.
PREFACE
This work treats of the fish from all the varied points of view of the
different branches of the study of Ichthyology. In general all traits
of the fish are discussed, those which the fish shares with other
animals most briefly, those which relate to the evolution of the group
and the divergence of its various classes and orders most fully. The
extinct forms are restored to their place in the series and discussed
along with those still extant.
In general, the writer has drawn on his own experience as an
ichthyologist, and with this on all the literature of the science.
Special obligations are recognized in the text. To Dr. Charles
H. Gilbert, he is indebted for a critical reading of most of his
proof-sheets; to Dr. Bashford Dean, for criticism of the proof-sheets
of the chapters on the lower fishes; to Dr. William Emerson Ritter, for
assistance in the chapters on _Protochordata_; to Dr. George Clinton
Price, for revision of the chapters on lancelets and lampreys, and to
Mr. George Clark, Secretary of Stanford University, for assistance of
various kinds, notably in the preparation of the index. To Dr. Theodore
Gill, he has been for many years constantly indebted for illuminating
suggestions, and to Dr. Barton Warren Evermann, for a variety of
favors. To Dr. Richard Rathbun, the writer owes the privilege of using
illustrations from the "Fishes of North and Middle America" by Jordan
and Evermann. The remaining plates were drawn for this work by Mary
H. Wellman, Kako Morita, and Sekko Shimada. Many of the plates are
original. Those copied from other authors are so indicated in the text.
No bibliography has been included in this work. A list of writers
so complete as to have value to the student would make a volume of
itself. The principal works and their authors are discussed in the
chapter on the History of Ichthyology, and with this for the present
the reader must be contented.
The writer has hoped to make a book valuable to technical students,
interesting to anglers and nature lovers, and instructive to all who
open its pages.
DAVID STARR JORDAN.
PALO ALTO, SANTA CLARA COUNTY, CAL.,
October, 1904.
ERRATA[1]
VOL. I
Frontispiece, for _Paramia quinqueviltata_ read _Paramia quinquevittata_
Page xiii, line 10, _for_ Filefish _read_ Tilefish
39, " 15, _for_ Science _read_ Sciences
52, lines 4 and 5, transpose hypocoracoid and hypercoracoid
115, line 24, for _Hexagramidæ_ read _Hexagrammidæ_
162, " 7, The female salmon does as much as the male in
covering the eggs.
169, last line, _for_ immmediately _read_ immediately
189, legend, _for_ Miaki _read_ Misaki
313, line 26, _for_ sand-pits _read_ sand-spits
322, " 7 and elsewhere, for Wood's Hole read Woods Hole
324, " 15, for _Roceus_ read _Roccus_
327, " next to last, for _masquinonqy_ read _masquinongy_
357, " 5, _for_ Filefish _read_ Tilefish
361, " 26, _for_ 255 feet _read_ 25 feet
368, " 26, _for_ infallibility _read_ fallibility
414, " 22, _for_ West Indies _read_ East Indies
419, " 23, _for_-99 _read_-96
420, " 28, _for_ were _read_ are
428, " 24, _for_ Geffroy, St. Hilaire _read_ Geoffroy St. Hilaire
428, " 25, _for_ William Kitchener Parker _read_ William
Kitchen Parker
462, " 32, for _Enterpneusta_ read _Enteropneusta_
CONTENTS
VOL. I.
CHAPTER I.
THE LIFE OF THE FISH (_Lepomis megalotis_).
PAGE
What is a Fish?--The Long-eared Sunfish.--Form of the Fish.--Face
of the Fish.--How the Fish Breathes.--Teeth of the Fish.--How the
Fish Sees.--Color of the Fish.--The Lateral Line.--The Fins of
the Fish.--The Skeleton of the Fish.--The Fish in Action.--The
Air-bladder.--The Brain of the Fish.--The Fish's Nest. 3
CHAPTER II.
THE EXTERIOR OF THE FISH.
Form of Body.--Measurement of the Fish.--The Scales or
Exoskeleton.--Ctenoid and Cycloid Scales.--Placoid Scales.--Bony
and Prickly Scales.--Lateral Line.--Function of the Lateral
Line.--The Fins of Fishes.--Muscles. 16
CHAPTER III.
THE DISSECTION OF THE FISH.
The Blue-green Sunfish.--The Viscera.--Organs of Nutrition.--The
Alimentary Canal.--The Spiral Valve.--Length of the Intestine. 26
CHAPTER IV.
THE SKELETON OF THE FISH.
Specialization of the Skeleton.--Homologies of Bones of
Fishes.--Parts of the Skeleton.--Names of Bones of Fishes.--Bones
of the Cranium.--Bones of the Jaws.--The Suspensorium of the
Mandible.--Membrane Bones of Head.--Branchial Bones.--The
Gill-arches.--The Pharyngeals.--The Vertebral Column.--The
Interneurals and Interhæmals.--The Pectoral Limb.--The
Shoulder-girdle.--The Posterior Limb.--Degeneration.--The Skeleton
in Primitive Fishes.--The Skeleton of Sharks.--The Archipterygium. 34
CHAPTER V.
MORPHOLOGY OF THE FINS OF FISHES.
Origin of the Fins of Fishes.--Origin of the Paired
Fins.--Development of the Paired Fins in the
Embryo.--Evidences of Palæontology.--Current Theories as
to Origin of Paired Fin.--Balfour's Theory of the Lateral
Fold.--Objections.--Objections to Gegenbaur's Theory.--Kerr's
Theory of Modified External Gills.--Uncertain Conclusions.--Forms
of the Tail in Fishes.--Homologies of the Pectoral Limb.--The
Girdle in Fishes other than Dipnoans. 62
CHAPTER VI.
THE ORGANS OF RESPIRATION.
How Fishes Breathe.--The Gill Structures.--The Air-bladder.--Origin
of the Air-bladder.--The Origin of Lungs.--The Heart of the
Fish.--The Flow of Blood. 91
CHAPTER VII.
THE NERVOUS SYSTEM.
The Nervous System.--The Brain of the Fish.--The Pineal Organ.--The
Brain of Primitive Fishes.--The Spinal Cord.--The Nerves. 109
CHAPTER VIII.
THE ORGANS OF SENSE.
The Organs of Smell.--The Organs of Sight.--The Organs of
Hearing.--Voices of Fishes.--The Sense of Taste.--The Sense of
Touch. 115
CHAPTER IX.
THE ORGANS OF REPRODUCTION.
The Germ-cells.--The Eggs of Fishes.--Protection of the
Eggs.--Sexual Modification. 124
CHAPTER X.
THE EMBRYOLOGY AND GROWTH OF FISHES.
Post-embryonic Development.--General Laws of Development.--The
Significance of Facts of Development.--The Development of the
Bony Fishes.--The Larval Development of Fishes.--Peculiar
Larval Forms.--The Development of Flounders.--Hybridism.--The
Age of Fishes.--Tenacity of Life.--Effect of Temperature
on Fishes.--Transportation of Fishes.--Reproduction of Lost
Parts.--Monstrosities among Fishes. 131
CHAPTER XI.
INSTINCTS, HABITS, AND ADAPTATIONS.
The Habits of Fishes.--Irritability of Animals.--Nerve-cells
and Fibers.--The Brain or Sensorium.--Reflex
Action.--Instinct.--Classification of Instincts.--Variability
of Instincts.--Adaptations to Environment.--Flight of
Fishes.--Quiescent Fishes.--Migratory Fishes.--Anadromous
Fishes.--Pugnacity of Fishes.--Fear and Anger in Fishes.--Calling
the Fishes.--Sounds of Fishes.--Lurking Fishes.--The Unsymmetrical
Eyes of the Flounder.--Carrying Eggs in the Mouth. 152
CHAPTER XII.
ADAPTATIONS OF FISHES.
Spines of the Catfishes.--Venomous Spines.--The Lancet of the
Surgeon-fish.--Spines of the Sting-ray.--Protection through
Poisonous Flesh of Fishes.--Electric Fishes.--Photophores or
Luminous Organs.--Photophores in the Iniomous Fishes.--Photophores
of Porichthys.--Globefishes.--Remoras.--Sucking-disks of
Clingfishes.--Lampreys and Hogfishes.--The Swordfishes.--The
Paddle-fishes.--The Sawfishes.--Peculiarities of Jaws and
Teeth.--The Angler-fishes.--Relation of Number of Vertebræ to
Temperature, and the Struggle for Existence.--Number of Vertebræ:
Soft-rayed Fishes; Spiny-rayed Fishes; Fresh-water Fishes; Pelagic
Fishes.--Variations in Fin-rays.--Relation of Numbers to Conditions
of Life.--Degeneration of Structures.--Conditions of Evolution
among Fishes. 179
CHAPTER XIII.
COLORS OF FISHES.
Pigmentation.--Protective Coloration.--Protective Markings.--Sexual
Coloration.--Nuptial Coloration.--Coral-reef Fishes.--Recognition
Marks.--Intensity of Coloration.--Fading of Pigments in
Spirits.--Variation in Pattern. 226
CHAPTER XIV.
GEOGRAPHICAL DISTRIBUTION OF FISHES.
Zoogeography.--General Laws of Distribution.--Species Absent
through Barriers.--Species Absent through Failure to Maintain
Foothold.--Species Changed through Natural Selection.--Extinction
of Species.--Barriers Checking Movements of Marine
Species.--Temperature the Central Fact in Distribution.--Agency
of Ocean Currents.--Centers of Distribution.--Distribution of
Marine Fishes.--Pelagic Fishes.--Bassalian Fishes.--Littoral
Fishes.--Distribution of Littoral Fishes by Coast Lines.--Minor
Faunal Areas.--Equatorial Fishes most Specialized.--Realms of
Distribution of Fresh-water Fishes.--Northern Zone.--Equatorial
Zone.--Southern Zone.--Origin of the New Zealand Fauna. 237
CHAPTER XV.
ISTHMUS BARRIERS SEPARATING FISH FAUNAS.
The Isthmus of Suez.--The Fish Fauna of Japan.--Fresh-water Faunas
of Japan.--Faunal Areas of Marine Fishes of Japan.--Resemblance
of Japanese and Mediterranean Fish Faunas.--Significance of
Resemblances.--Differences between Japanese and Mediterranean Fish
Faunas.--Source of Faunal Resemblances.--Effects of Direction of
Shore Lines.--Numbers of Genera in Different Faunas.--Significance
of Rare Forms.--Distribution of Shore-fishes.--Extension
of Indian Fauna.--The Isthmus of Suez as a Barrier to
Distribution.--Geological Evidences of Submergence of Isthmus of
Suez.--The Cape of Good Hope as a Barrier to Fishes.--Relations of
Japan to the Mediterranean Explained by Present Conditions.--The
Isthmus of Panama as a Barrier to Distribution.--Unlikeness
of Species on the Shores of the Isthmus of Panama.--Views of
Dr. Günther on the Isthmus of Panama.--Catalogue of Fishes of
Panama.--Conclusions of Evermann & Jenkins.--Conclusions of Dr.
Hill.--Final Hypothesis as to Panama. 255
CHAPTER XVI.
DISPERSION OF FRESH-WATER FISHES.
The Dispersion of Fishes.--The Problem of Oatka
Creek.--Generalizations as to Dispersion.--Questions Raised by
Agassiz.--Conclusions of Cope.--Questions Raised by Cope.--Views
of Günther.--Fresh-water Fishes of North America.--Characters of
Species.--Meaning of Species.--Special Creation Impossible.--Origin
of American Species of Fishes. 282
CHAPTER XVII.
DISPERSION OF FRESH-WATER FISHES. (_Continued._)
Barriers to Dispersion of Fresh-water Fishes: Local
Barriers.--Favorable Waters Have Most Species.--Watersheds.--How
Fishes Cross Watersheds.--The Suletind.--The
Cassiquiare.--Two-Ocean Pass.--Mountain Chains.--Upland
Fishes.--Lowland Fishes.--Cuban Fishes.--Swampy Watersheds.--The
Great Basin of Utah.--Arctic Species in Lakes.--Causes of
Dispersion still in Operation. 297
CHAPTER XVIII.
FISHES AS FOOD FOR MAN.
The Flesh of Fishes.--Relative Rank of Food-fishes.--Abundance
of Food-fishes.--Variety of Tropical Fishes.--Economic
Fisheries.--Angling. 320
CHAPTER XIX.
DISEASES OF FISHES.
Contagious Diseases: Crustacean Parasites.--Myxosporidia or
Parasitic Protozoa.--Parasitic Worms: Trematodes, Cestodes.--The
Worm of the Yellowstone.--The Heart Lake Tape-worm.--Thorn-head
Worms.--Nematodes.--Parasitic Fungi.--Earthquakes.--Mortality of
Filefish. 340
CHAPTER XX.
THE MYTHOLOGY OF FISHES.
The Mermaid.--The Monkfish.--The Bishop-fish.--The Sea-serpent. 359
CHAPTER XXI.
THE CLASSIFICATION OF FISHES.
Taxonomy.--Defects in Taxonomy.--Analogy and Homology.--Coues
on Classification.--Species as Twigs of a Genealogical
Tree.--Nomenclature.--The Conception of Genus and
Species.--The Trunkfishes.--Trinomial Nomenclature.--Meaning
of Species.--Generalization and Specialization.--High and Low
Forms.--The Problem of the Highest Fishes. 367
CHAPTER XXII.
THE HISTORY OF ICHTHYOLOGY.
Aristotle.--Rondelet.--Marcgraf.--Osbeck.--Artedi.--Linnæus.--
Forskål.--Risso.--Bloch.--Lacépède.--Cuvier.--Valenciennes.--
Agassiz.--Bonaparte.--Günther.--Boulenger.--Le Sueur.--Müller.--
Gill.--Cope.--Lütken.--Steindachner.--Vaillant.--Bleeker.--
Schlegel.--Poey.--Day.--Baird.--Garman.--Gilbert.--Evermann.--
Eigenmann.--Zittel.--Traquair.--Woodward.--Dean.--Eastman.--Hay.--
Gegenbaur.--Balfour.--Parker.--Dollo. 387
CHAPTER XXIII.
THE COLLECTION OF FISHES.
How to Secure Fishes.--How to Preserve Fishes.--Value of
Formalin.--Records of Fishes.--Eternal Vigilance. 429
CHAPTER XXIV.
THE EVOLUTION OF FISHES.
The Geological Distribution of Fishes.--The Earliest
Sharks.--Devonian Fishes.--Carboniferous Fishes.--Mesozoic
Fishes.--Tertiary Fishes.--Factors of Extinction.--Fossilization
of a Fish.--The Earliest Fishes.--The Cyclostomes.--The
Ostracophores.--The Arthrodires.--The Sharks.--Origin of the
Shark.--The Chimæras.--The Dipnoans.--The Crossopterygians.--The
Actinopteri.--The Bony Fishes. 435
CHAPTER XXV.
THE PROTOCHORDATA.
The Chordate Animals.--The Protochordates.--Other Terms Used
in Classification.--The Enteropneusta.--Classification of
Enteropneusta.--Family Harrimaniidæ.--Balanoglossidæ.--Low
Organization of Harrimaniidæ. 460
CHAPTER XXVI.
THE TUNICATES, OR ASCIDIANS.
Structure of Tunicates.--Development of
Tunicates.--Reproduction of Tunicates.--Habits of
Tunicates.--Larvacea.--Ascidiacea.--Thaliacea.--Origin of
Tunicates.--Degeneration of Tunicates. 467
CHAPTER XXVII.
THE LEPTOCARDII, OR LANCELETS.
The Lancelet.--Habits of Lancelets.--Species of Lancelets.--Origin
of Lancelets. 482
CHAPTER XXVIII.
THE CYCLOSTOMES, OR LAMPREYS.
The Lampreys.--Structure of the Lamprey.--Supposed Extinct
Cyclostomes.--Conodontes.--Orders of Cyclostomes.--The
Hyperotreta, or Hagfishes.--The Hyperoartia, or Lampreys.--Food
of Lampreys.--Metamorphosis of Lampreys.--Mischief Done by
Lampreys.--Migration or "Running" of Lampreys.--Requisite
Conditions for Spawning with Lampreys.--The Spawning Process with
Lampreys.--What Becomes of Lampreys after Spawning? 486
CHAPTER XXIX.
THE CLASS ELASMOBRANCHII, OR SHARK-LIKE FISHES.
The Sharks.--Characters of Elasmobranchs.--Classification
of Elasmobranchs.--Subclasses of Elasmobranchs.--The
Selachii.--Hasse's Classification of Elasmobranchs.--Other
Classifications of Elasmobranchs.--Primitive Sharks.--Order
Pleuropterygii.--Order Acanthodii.--Dean on Acanthodii.--Order
Ichthyotomi. 506
CHAPTER XXX.
THE TRUE SHARKS.
Order Notidani.--Family Hexanchidæ.--Family
Chlamydoselachidæ.--Order Asterospondyli.--Suborder
Cestraciontes.--Family Heterodontidæ.--Edestus and its
Allies.--Onchus.--Family Cochliodontidæ.--Suborder Galei.--Family
Scyliorhinidæ.--The Lamnoid, or Mackerel-sharks.--Family
Mitsukurinidæ, the Goblin-sharks.--Family Alopiidæ,
or Thresher-sharks.--Family Pseudotriakidæ.--Family
Lamnidæ.--Man-eating Sharks.--Family Cetorhinidæ, or Basking
Sharks.--Family Rhineodontidæ.--The Carcharioid Sharks, or
Requins.--Family Sphyrnidæ, or Hammer-head Sharks.--The
Order of Tectospondyli.--Suborder Cyclospondyli.--Family
Squalidæ.--Family Dalatiidæ.--Family Echinorhinidæ.--Suborder
Rhinæ.--Family Pristiophoridæ, or Saw-sharks.--Suborder
Batoidei, or Rays.--Pristididæ, or Sawfishes.--Rhinobatidæ,
or Guitar-fishes.--Rajidæ, or Skates.--Narcobatidæ,
or Torpedoes.--Petalodontidæ.--Dasyatidæ, or
Sting-rays.--Myliobatidæ.--Family Psammodontidæ.--Family Mobulidæ. 523
CHAPTER XXXI.
THE HOLOCEPHALI, OR CHIMÆRAS.
The Chimæras.--Relationship of Chimæras.--Family
Chimæridæ.--Rhinochimæridæ.--Extinct
Chimæroids.--Ichthyodorulites. 561
CHAPTER XXXII.
THE CLASS OSTRACOPHORI.
Ostracophores.--Nature of Ostracophores.--Orders of
Ostracophores.--Order Heterostraci.--Order Osteostraci.--Order
Antiarcha.--Order Anaspida. 568
CHAPTER XXXIII.
ARTHRODIRES.
The Arthrodires.--Occurrence of
Arthrodires.--Arthrognathi.--Anarthrodira.--Stegothalami.--
Arthrodira.--Temnothoraci.--Arthrothoraci.--Relations of
Arthrodires.--Suborder Cycliæ.--Palæospondylus.--Gill on
Palæospondylus.--Views as to the Relationships of Palæospondylus:
Huxley, Traquair, 1890. Traquair, 1893. Traquair, 1897. Smith
Woodward, 1892. Dawson, 1893. Gill, 1896. Dean, 1896. Dean, 1898.
Parker & Haswell, 1897. Gegenbaur, 1898.--Relationships of
Palæospondylus 581
CHAPTER XXXIV.
THE CROSSOPTERYGII.
Class Teleostomi.--Subclass Crossopterygii.--Order of
Amphibians.--The Fins of Crossopterygians.--Orders of
Crossopterygians.--Haplistia.--Rhipidistia.--Megalichthyidæ.--Order
Actinistia.--Order Cladistia.--The Polypteridæ 598
CHAPTER XXXV.
SUBCLASS DIPNEUSTI, OR LUNGFISHES.
The Lungfishes.--Classification of Dipnoans.--Order
Ctenodipterini.--Order Sirenoidei.--Family
Ceratodontidæ.--Development of Neoceratodus.--Lepidosirenidæ.--Kerr
on the Habits of Lepidosiren 609
FOOTNOTES:
[1] For most of this list of errata I am indebted to the kindly
interest of Dr. B. W. Evermann.
LIST OF ILLUSTRATIONS
VOL. I.
PAGE
_Lepomis megalotis_, Long-eared Sunfish 2
_Lepomis megalotis_, Long-eared Sunfish 4
_Eupomotis gibbosus_, Common Sunfish 7
_Ozorthe dictyogramma_, a Japanese Blenny 9
_Eupomotis gibbosus_, Common Sunfish 13
_Monocentris japonicas_, Pine-cone Fish 16
_Diodon hystrix_, Porcupine-fish 17
_Nemichthys avocetta_, Thread-eel 17
_Hippocampus hudsonius_, Sea-horse 17
_Peprilus paru_, Harvest-fish 18
_Lophius litulon_, Anko or Fishing-frog 18
_Epinephelus adscensionis_, Rock-hind or Cabra Mora 20
Scales of _Acanthoessus bronni_ 21
Cycloid Scale 22
_Porichthys porosissimus_, Singing-fish 23
_Apomotis cyanellus_, Blue-green Sunfish 27
_Chiasmodon niger_, Black Swallower 29
Jaws of a Parrot-fish, _Sparisoma aurofrenatum_ 30
_Archosargus probatocephalus_, Sheepshead 31
_Campostoma anomalum_, Stone-roller 33
_Roccus lineatus_, Striped Bass 35
_Roccus lineatus._ Lateral View of Cranium 36
_Roccus lineatus._ Superior View of Cranium 37
_Roccus lineatus._ Inferior View of Cranium 38
_Roccus lineatus_. Posterior View of Cranium 40
_Roccus lineatus._ Face-bones, Shoulder and Pelvic Girdles, and
Hyoid Arch 42
Lower Jaw of _Amia calva_, showing Gular Plate 43
_Roccus lineatus._ Branchial Arches 46
Pharyngeal Bone and Teeth of European Chub, _Leuciscus cephalus_ 47
Upper Pharyngeals of Parrot-fish, _Scarus strongylocephalus_ 47
Lower Pharyngeal Teeth of Parrot-fish, _Scarus strongylocephalus_ 47
Pharyngeals of Italian Parrot-fish, _Sparisoma cretense_ 48
_Roccus lineatus_, Vertebral Column and Appendages 48
Basal Bone of Dorsal Fin, _Holoptychius leptopterus_ 49
Inner View of Shoulder-girdle of Buffalo-fish, _Ictiobus bubalus_
51
_Pterophryne tumida_, Sargassum-fish. 52
Shoulder-girdle of _Sebastolobus alascanus_. 52
Cranium of _Sebastolobus alascanus_. 53
Lower Jaw and Palate of _Sebastolobus alascanus_. 54
Maxillary and Premaxillary of _Sebastolobus alascanus_. 55
Part of Skeleton of _Selene vomer_. 55
Hyostylic Skull of _Chiloscyllium indicum_, a Scyliorhinoid Shark. 56
Skull of _Heptranchias indicus_, a Notidanoid Shark. 56
Basal Bones of Pectoral Fin of Monkfish, _Squatina_. 56
Pectoral Fin of _Heterodontus philippi_. 57
Pectoral Fin of _Heptranchias indicus_. 57
Shoulder-girdle of a Flounder, _Paralichthys californicus_. 58
Shoulder-girdle of a Toadfish, _Batrachoides pacifici_. 59
Shoulder-girdle of a Garfish, _Tylosurus fodiator_. 59
Shoulder-girdle of a Hake, _Merluccius productus_. 60
_Cladoselache fyleri_, Restored. 65
Fold-like Pectoral and Ventral Fins of _Cladoselache fyleri_. 65
Pectoral Fin of a Shark, _Chiloscyllium_. 66
Skull and Shoulder-girdle of _Neoceratodus forsteri_, showing
archipterygium. 68
_Acanthoessus wardi_. 69
Shoulder-girdle of _Acanthoessus_. 69
Pectoral Fin of _Pleuracanthus_. 69
Shoulder-girdle of _Polypterus bichir_. 70
Arm of a Frog. 71
_Pleuracanthus decheni_. 74
Embryos of _Heterodontus japonicas_, a Cestraciont Shark. 75
_Polypterus congicus_, a Crossopterygian Fish with External Gills. 78
Heterocercal Tail of Sturgeon, _Acipenser sturio_. 80
Heterocercal Tail of Bowfin, _Amia calva_. 82
Heterocercal Tail of Garpike, _Lepisosteus osseus_. 82
_Coryphænoides carapinus_, showing Leptocercal Tail. 83
Heterocercal Tail of Young Trout, _Salmo fario_. 83
Isocercal Tail of Hake, _Merluccius productus_. 84
Homocercal Tail of a Flounder, _Paralichthys californicus_. 84
Gephyrocercal Tail of _Mola mola_. 85
Shoulder-girdle of _Amia calva_. 86
Shoulder-girdle of a Sea-catfish, _Selenaspis dowi_. 86
Clavicles of a Sea-catfish, _Selenaspis dowi_. 87
Shoulder-girdle of a Batfish, _Ogcocephalus radiatus_. 88
Shoulder-girdle of a Threadfin, _Polydactylus approximans_. 89
Gill-basket of Lamprey. 92
Weberian Apparatus and Air-bladder of Carp. 93
Brain of a Shark, _Squatina squatina_. 110
Brain of _Chimæra monstrosa_. 110
Brain of _Polypterus annectens_. 110
Brain of a Perch, _Perca flavescens_. 111
_Petromyzon marinus unicolor._ Head of Lake Lamprey, showing Pineal
Body. 111
_Chologaster cornutus_, Dismal-swamp Fish. 116
_Typhlichthys subterraneus_, Blind Cavefish. 116
_Anableps dovii_, Four-eyed Fish. 117
_Ipnops murrayi._ 118
_Boleophthalmus chinensis_, Pond-skipper. 118
_Lampetra wilderi_, Brook Lamprey. 120
_Branchiostoma lanceolatum_, European Lancelet. 120
_Pseudupeneus maculatus_, Goatfish. 122
_Xiphophorus helleri_, Sword-tail Minnow. 124
_Cymatogaster aggregatus_, White Surf-fish, Viviparous, with
Young. 125
_Goodea luitpoldi_, a Viviparous Fish. 126
Egg of _Callorhynchus antarcticus_, the Bottle-nosed Chimæra. 127
Egg of the Hagfish, _Myxine limosa_. 127
Egg of Port Jackson Shark, _Heterodontus philippi_. 128
Development of Sea-bass, _Centropristes striatus_. 135
_Centropristes striatus_, Sea-bass. 137
_Xiphias gladius_, Young Sword-fish. 139
_Xiphias gladius_, Sword-fish. 139
Larva of the Sail-fish, _Istiophorus_, Very Young. 140
Larva of Brook Lamprey, _Lampetra wilderi_, before Transformation.
140
_Anguilla chrisypa_, Common Eel. 140
Larva of Common Eel, _Anguilla chrisypa_, called _Leptocephalus
grassii_. 141
Larva of Sturgeon, _Acipenser sturio_. 141
Larva of _Chætodon sedentarius_. 142
_Chætodon capistratus_, Butterfly-fish. 142
_Mola mola_, Very Early Larval Stage of Headfish, called _Centaurus
boöps_. 143
_Mola mola_, Early Larval Stage called _Molacanthus nummularis_. 144
_Mola mola_, Advanced Larval Stage. 144
_Mola mola_, Headfish, Adult. 146
_Albula vulpes_, Transformation of Ladyfish from Larva to Young. 147
Development of the Horsehead-fish, _Selene vomer_. 148
_Salanx hyalocranius_, Ice-fish. 149
_Dallia pectoralis_, Alaska Blackfish. 149
_Ophiocephalus barca_, Snake-headed China-fish. 150
_Carassius auratus_, Monstrous Goldfish. 151
Jaws of _Nemichthys avocetta_. 156
_Cypsilurus californicus_, Flying-fish. 157
_Ammocrypta clara_, Sand-darter. 158
_Fierasfer acus_, Pearl-fish, issuing from a Holothurian. 159
_Gobiomorus gronovii_, Portuguese Man-of-war Fish. 160
Tide Pools of Misaki. 161
_Ptychocheilus oregonensis_, Squaw-fish. 162
_Ptychocheilus grandis_, Squaw-fish, Stranded as the Water Falls. 164
Larval Stages of _Platophrys podas_, a Flounder of the
Mediterranean, showing Migration of Eye. 174
_Platophrys lunatus_, the Wide-eyed Flounder. 175
Young Flounder Just Hatched, with Symmetrical Eyes. 175
_Pseudopleuronectes americanus_, Larval Flounder. 176
_Pseudopleuronectes americanus_, Larval Flounder (more advanced
stage). 176
Face View of Recently-hatched Flounder. 177
_Schilbeodes furiosus_, Mad-Tom. 179
_Emmydrichthys vulcanus_, Black Nohu or Poison-fish. 180
_Teuthis bahianus_, Brown Tang. 181
_Stephanolepis hispidus_, Common Filefish. 182
_Tetraodon meleagris._ 183
_Balistes carolinensis_, the Trigger-fish. 184
_Narcine brasiliensis_, Numbfish. 185
_Torpedo electricus_, Electric Catfish. 186
_Astroscopus guttatus_, Star-gazer. 187
_Æthoprora lucida_, Headlight-fish. 188
_Corynolophus reinhardti_, showing Luminous Bulb. 188
_Etmopterus lucifer._ 189
_Argyropelecus olfersi._ 190
Luminous Organs and Lateral Line of Midshipman, _Porichthys
notatus_. 192
Cross-section of Ventral Phosphorescent Organ of Midshipman,
_Porichthys notatus_. 193
Section of Deeper Portion of Phosphorescent Organ, _Porichthys
notatus_. 194
_Leptecheneis naucrates_, Sucking-fish or Pegador. 197
_Caularchus mæandricus_, Clingfish. 198
_Polistotrema stouti_, Hagfish. 199
_Pristis zysron_, Indian Sawfish. 200
_Pristiophorus japonicus_, Saw-shark. 201
Skeleton of Pike, _Esox lucius_. 203
Skeleton of Red Rockfish, _Sebastodes miniatus_. 214
Skeleton of a Spiny-rayed Fish of the Tropics, _Holacanthus
ciliaris_. 214
Skeleton of the Cowfish, _Lactophrys tricornis_. 215
_Crystallias matsushimæ_, Liparid. 218
_Sebastichthys maliger_, Yellow-backed Rockfish. 218
_Myoxocephalus scorpius_, European Sculpin. 219
_Hemitripterus americanus_, Sea-raven. 220
_Cyclopterus lumpus_, Lumpfish. 220
_Psychrolutes paradoxus_, Sleek Sculpin. 221
_Pallasina barbata_, Agonoid-fish. 221
_Amblyopsis spelæus_, Blindfish of the Mammoth Cave. 221
_Lucifuga subterranea_, Blind Brotula. 222
_Hypsypops rubicunda_, Garibaldi. 227
_Synanceia verrucosa_, Gofu or Poison-fish. 229
_Alticus saliens_, Lizard-skipper. 230
_Etheostoma camurum_, Blue-breasted Darter. 231
_Liuranus semicinctus_ and _Chlevastes colubrinus_, Snake-eels. 233
Coral Reef at Apia. 234
_Rudarius ercodes_, Japanese Filefish. 241
_Tetraodon setosus_, Globefish. 244
_Dasyatis sabina_, Sting-ray. 246
_Diplesion blennioides_, Green-sided Darter. 247
_Hippocampus mohnikei_, Japanese Sea-horse. 250
_Archoplites interruptus_, Sacramento Perch. 258
Map of the Continents, Eocene Time. 270
_Caulophryne jordani_, Deep-sea Fish of Gulf Stream. 276
_Exerpes asper_, Fish of Rock-pools, Mexico. 276
_Xenocys jessiæ._ 279
_Ictalurus punctatus_, Channel Catfish. 280
Drawing the Net on the Beach of Hilo, Hawaii. 281
_Semotilus atromaculatus_, Horned Dace. 285
_Leuciscus lineatus_, Chub of the Great Basin. 287
_Melletes papilio_, Butterfly Sculpin. 288
_Scartichthys enosimæ_, a Fish of the Rock-pools of the Sacred
Island of Enoshima, Japan. 294
_Halichoeres bivittatus_, the Slippery Dick. 297
_Peristedion miniatum._ 299
Outlet of Lake Bonneville. 303
_Hypocritichthys analis_, Silver Surf-fish. 309
_Erimyzon sucetta_, Creekfish or Chub-sucker. 315
_Thaleichthys pretiosus_, Eulachon or Ulchen. 320
_Plecoglossus altivelis_, the Japanese Ayu. 321
_Coregonus clupeiformis_, the Whitefish. 321
_Mullus auratus_, the Golden Surmullet. 322
_Scomberomorus maculatus_, the Spanish Mackerel. 322
_Lampris luna_, the Opah or Moonfish. 323
_Pomatomus saltatrix_, the Bluefish. 324
_Centropomus undecimalis_, the Robalo. 324
_Chætodipterus faber_, the Spadefish. 325
_Micropterus dolomieu_, the Small-mouthed Black Bass. 325
_Salvelinus fontinalis_, the Speckled Trout. 326
_Salmo irideus_, the Rainbow Trout. 326
_Salvelinus oquassa_, the Rangeley Trout. 326
_Salmo gairdneri_, the Steelhead Trout. 327
_Salmo henshawi_, the Tahoe Trout. 327
_Salvelinus malma_, the Dolly Varden Trout. 327
_Thymallus signifer_, the Alaska Grayling. 328
_Esox lucius_, the Pike. 328
_Pleurogrammus monopterygius_, the Atka-fish. 328
_Chirostoma humboldtianum_, the Pescado blanco. 329
_Pseudupeneus maculatus_, the Red Goatfish. 329
_Pseudoscarus guacamaia_, Great Parrot-fish. 330
_Mugil cephalus_, Striped Mullet. 330
_Lutianus analis_, Mutton-snapper. 331
_Clupea harengus_, Herring. 331
_Gadus callarias_, Codfish. 331
_Scomber scombrus_, Mackerel. 332
_Hippoglossus hippoglossus_, Halibut. 332
Fishing for Ayu with Cormorants. 333
Fishing for Ayu. Emptying Pouch of Cormorant. 335
Fishing for Tai, Tokyo Bay. 338
_Brevoortia tyrannus_, Menhaden. 340
_Exonautes unicolor_, Australian Flying-fish. 341
_Rhinichthys atronasus_, Black-nosed Dace. 342
_Notropis hudsonius_, White Shiner. 343
_Ameiurus catus_, White Catfish. 344
_Catostomus ardens_, Sucker. 348
_Oncorhynchus tschawytscha_, Quinnat Salmon. 354
_Oncorhynchus tschawytscha_, Young Male. 355
_Ameiurus nebulosus_, Catfishes. 358
"Le Monstre Marin en Habit de Moine". 360
"Le Monstre Marin en Habit d'Évêque". 361
_Regalecus russelli_, Oarfish. 362
_Regalecus glesne_, Glesnæs Oarfish. 363
_Nemichthys avocetta_, Thread-eel. 365
_Lactophrys tricornis_, Horned Trunkfish. 373
_Ostracion cornutum_, Horned Trunkfish. 376
_Lactophrys bicaudalis_, Spotted Trunkfish. 377
_Lactophrys bicaudalis_, Spotted Trunkfish (Face). 377
_Lactophrys triqueter_, Spineless Trunkfish. 378
_Lactophrys trigonus_, Hornless Trunkfish. 378
_Lactophrys trigonus_, Hornless Trunkfish (Face). 379
Bernard Germain de Lacépède. 399
Georges Dagobert Cuvier. 399
Louis Agassiz. 399
Johannes Müller. 399
Albert Günther. 403
Franz Steindachner. 403
George Albert Boulenger. 403
Robert Collett. 403
Spencer Fullerton Baird. 407
Edward Drinker Cope. 407
Theodore Nicholas Gill. 407
George Brown Goode. 407
Johann Reinhardt. 409
Edward Waller Claypole. 409
Carlos Berg. 409
Edgar R. Waite. 409
Felipe Poey y Aloy. 413
Léon Vaillant. 413
Louis Dollo. 413
Decio Vinciguerra. 413
Bashford Dean. 417
Kakichi Mitsukuri. 417
Carl H. Eigenmann. 417
Franz Hilgendorf. 417
David Starr Jordan. 421
Herbert Edson Copeland. 421
Charles Henry Gilbert. 421
Barton Warren Evermann. 421
Ramsay Heatley Traquair. 425
Arthur Smith Woodward. 425
Karl A. Zittel. 425
Charles R. Eastman. 425
Fragment of Sandstone from Ordovician Deposits. 435
Fossil Fish Remains from Ordovician Rocks. 436
_Dipterus valenciennesi._ 437
_Hoplopteryx lewesiensis._ 438
_Paratrachichthys prosthemius_, Berycoid fish. 439
_Cypsilurus heterurus_, Flying-fish. 440
_Lutianidæ_, Schoolmaster Snapper. 440
_Pleuronichthys decurrens_, Decurrent Flounder. 441
_Cephalaspis lyelli_, Ostracophore. 444
_Dinichthys intermedius_, Arthrodire. 445
_Lamna cornubica_, Mackerel-shark or Salmon-shark. 447
_Raja stellulata_, Star-spined Ray. 448
_Harriotta raleighiana_, Deep-sea Chimæra. 449
_Dipterus valenciennesi_, Extinct Dipnoan. 449
_Holoptychius giganteus_, Extinct Crossopterygian. 451
_Platysomus gibbosus_, Ancient Ganoid fish. 452
_Lepisosteus platystomus_, Short-nosed Gar. 452
_Palæoniscum macropomum_, Primitive Ganoid fish. 453
_Diplomystus humilis_, Fossil Herring. 453
_Holcolepis lewesiensis_. 454
_Elops saurus_, Ten-pounder. 454
_Apogon semilineatus_, Cardinal-fish. 455
_Pomolobus æstivalis_, Summer Herring. 455
_Bassozetus catena._ 456
_Trachicephalus uranoscopus._ 456
_Chlarias breviceps_, African Catfish. 457
_Notropis whipplii_, Silverfin. 457
_Gymnothorax moringa._ 458
_Seriola lalandi_, Amber-fish. 458
Geological Distribution of the Families of Elasmobranchs. 459
"Tornaria" Larva of _Glossobalanus minutus_. 463
_Glossobalanus minutus._ 464
_Harrimania maculosa._ 465
Development of Larval Tunicate to Fixed Condition. 471
Anatomy of Tunicate. 472
_Ascidia adhærens._ 474
_Styela yacutatensis._ 475
_Styela greeleyi._ 476
_Cynthia superba._ 476
_Botryllus magnus_, Compound Ascidian. 477
_Botryllus magnus._ 478
_Botryllus magnus_, a Single Zooid. 479
_Aplidiopsis jordani_, a Compound Ascidian. 479
_Oikopleura_, Adult Tunicate of Group Larvacea. 480
_Branchiostoma californiense_, California Lancelet. 484
Gill-basket of Lamprey. 485
_Polygnathus dubium._ 488
_Polistotrema stouti_, Hagfish. 489
_Petromyzon marinus_, Lamprey. 491
_Petromyzon marinus unicolor_, Mouth Lake Lamprey. 492
_Lampetra wilderi_, Sea Larvæ Brook Lamprey. 492
_Lampetra wilderi_, Mouth Brook Lamprey. 492
_Lampetra camtschatica_, Kamchatka Lamprey. 495
_Entosphenus tridentatus_, Oregon Lamprey. 496
_Lampetra wilderi_, Brook Lamprey. 505
Fin-spine of _Onchus tenuistriatus_. 509
Section of Vertebræ of Sharks, showing Calcification. 510
_Cladoselache fyleri._ 514
_Cladoselache fyleri_, Ventral View. 515
Teeth of _Cladoselache fyleri_. 515
_Acanthoessus wardi._ 515
_Diplacanthus crassissimus._ 517
_Climatius scutiger._ 518
_Pleuracanthus decheni._ 519
_Pleuracanthus decheni_, Restored. 520
Head-bones and Teeth of _Pleuracanthus decheni_. 520
Teeth of _Didymodus bohemicus_. 520
Shoulder-girdle and Pectoral Fins of _Cladodus neilsoni_. 521
Teeth of _Cladodus striatus_. 522
_Hexanchus griseus_, Griset or Cow-shark. 523
Teeth of _Heptranchias indicus_. 524
_Chlamydoselachus anguineus_, Frill-shark. 525
_Heterodontus francisci_, Bullhead-shark. 526
Lower Jaw of _Heterodontus philippi_. 526
Teeth of Cestraciont Sharks. 527
Egg of Port Jackson Shark, _Heterodontus philippi_. 527
Tooth of _Hybodus delabechei_. 528
Fin-spine of _Hybodus basanus_. 528
Fin-spine of _Hybodus reticulatus_. 528
Fin-spine of _Hybodus canaliculatus_. 529
Teeth of Cestraciont Sharks. 529
_Edestus vorax_, Supposed to be a Whorl of Teeth. 529
_Helicoprion bessonowi_, Teeth of. 530
Lower Jaw of _Cochliodus contortus_. 531
_Mitsukurina owstoni_, Goblin-shark. 535
_Scapanorhynchus lewisi_, Under Side of Snout. 536
Tooth of _Lamna cuspidata_. 537
_Isuropsis dekayi_, Mackerel-shark. 537
Tooth of _Isurus hastalis_. 538
_Carcharodon mega odon._ 539
_Cetorhinus maximus_, Basking-shark. 540
_Galeus zyopterus_, Soup-fin Shark. 541
_Carcharias lamia_, Cub-shark. 542
Teeth of _Corax pristodontus_. 543
_Sphyrna zygæna_, Hammer-head Shark. 544
_Squalus acanthias_, Dogfish. 545
_Etmopterus lucifer._ 546
Brain of Monkfish, _Squatina squatina_. 547
_Pristiophorus japonicus_, Saw-shark. 548
_Pristis pectinatus_, Sawfish. 550
_Rhinobatus lentiginosus_, Guitar-fish. 551
_Raja erinacea_, Common Skate. 552
_Narcine brasiliensis_, Numbfish. 553
Teeth of _Janassa linguæformis_. 554
_Polyrhizodus radicans._ 555
_Dasyatis sabina_, Sting-ray. 556
_Aëtobatis narinari_, Eagle-ray. 558
_Manta birostris_, Devil-ray or Sea-devil. 559
Skeleton of _Chimæra monstrosa_. 564
_Chimæra colliei_, Elephant-fish. 565
_Odontotodus schrencki_, Ventral Side. 570
_Odontotodus schrencki_, Dorsal Side. 570
Head of _Odontotodus schrencki_, from the Side. 571
_Limulus polyphemus_, Horseshoe Crab. 572
_Lanarkia spinosa._ 574
_Drepanaspis gmundenensis._ 575
_Pteraspis rostrata._ 575
_Cephalaspis lyelli_, Restored. 576
_Cephalaspis dawsoni._ 577
_Pterichthyodes testudinarius._ 578
_Pterichthyodes testudinarius_, Side View. 579
_Birkenia elegans._ 579
_Lasianius problematicus._ 580
_Coccosteus cuspidatus_, Restored. 582
Jaws of _Dinichthys hertzeri_. 583
_Dinichthys intermedius_, an Arthrodire. 584
_Palæospondylus gunni._ 591
Shoulder-girdle of _Polypterus bichir_. 600
Arm of a Frog. 601
_Polypterus congicus_, a Crossopterygian Fish. 602
Basal Bone of Dorsal Fin, _Holoptychius leptopterus_. 603
_Gyroptychius microlepidotus._ 604
_Coelacanthus elegans_, showing Air-bladder. 604
_Undina gulo._ 605
Lower Jaw of _Polypterus bichir_, from Below. 606
_Polypterus congicus._ 607
_Polypterus delhezi._ 607
_Erpetoichthys calabaricus._ 608
Shoulder-girdle of _Neoceratodus forsteri_. 609
_Phaneropleuron andersoni._ 613
Teeth of _Ceratodus runcinatus_. 614
_Neoceratodus forsteri._ 614
Archipterygium of _Neoceratodus forsteri_. 614
Upper jaw of _Neoceratodus forsteri_. 615
Lower Jaw of _Neoceratodus forsteri_. 616
Adult Male of _Lepidosiren paradoxa_. 619
_Lepidosiren paradoxa._ Embryo Three Days before Hatching; Larva
Thirteen Days after Hatching. 620
Larva of _Lepidosiren paradoxa_ Forty Days after Hatching. 621
Larva of _Lepidosiren paradoxa_ Thirty Days after Hatching. 621
Larva of _Lepidosiren paradoxa_ Three Months after Hatching. 621
_Protopterus dolloi._ 622
[Illustration: FIG. 1.--Long-eared Sunfish, _Lepomis megalotis_
(Rafinesque). (From life by R. W. Shufeldt.)--Page 2.]
CHAPTER I
THE LIFE OF THE FISH
A POPULAR ACCOUNT OF THE LIFE OF THE LONG-EARED
SUNFISH, _LEPOMIS MEGALOTIS_
=What is a Fish?=--A fish is a back-boned animal which lives in the
water and cannot ever live very long anywhere else. Its ancestors have
always dwelt in water, and most likely its descendents will forever
follow their example. So, as the water is a region very different from
the fields or the woods, a fish in form and structure must be quite
unlike all the beasts and birds that walk or creep or fly above ground,
breathing air and being fitted to live in it. There are a great many
kinds of animals called fishes, but in this all of them agree: all have
some sort of a back-bone, all of them breathe their life long by means
of gills, and none have fingers or toes with which to creep about on
land.
=The Long-eared Sunfish.=--If we would understand a fish, we must first
go and catch one. This is not very hard to do, for there are plenty
of them in the little rushing brook or among the lilies of the pond.
Let us take a small hook, put on it an angleworm or a grasshopper,--no
need to seek an elaborate artificial fly,--and we will go out to the
old "swimming-hole" or the deep eddy at the root of the old stump where
the stream has gnawed away the bank in changing its course. Here we
will find fishes, and one of them will take the bait very soon. In one
part of the country the first fish that bites will be different from
the first one taken in some other. But as we are fishing in the United
States, we will locate our brook in the centre of population of our
country. This will be to the northwest of Cincinnati, among the low
wooded hills from which clear brooks flow over gravelly bottoms toward
the Ohio River. Here we will catch sunfishes of certain species, or
maybe rock bass or catfish: any of these will do for our purpose. But
one of our sunfishes is especially beautiful--mottled blue and golden
and scarlet, with a long, black, ear-like appendage backward from his
gill-covers--and this one we will keep and hold for our first lesson
in fishes. It is a small fish, not longer than your hand most likely,
but it can take the bait as savagely as the best, swimming away with it
with such force that you might think from the vigor of its pull that
you have a pickerel or a bass. But when it comes out of the water you
see a little, flapping, unhappy, living plate of brown and blue and
orange, with fins wide-spread and eyes red with rage.
[Illustration: FIG. 2.--Long-eared Sunfish, _Lepomis megalotis_
(Rafinesque). (From Clear Creek, Bloomington, Indiana.) Family
_Centrarchidæ_.]
=Form of the Fish.=--And now we have put the fish into a bucket of
water, where it lies close to the bottom. Then we take it home and
place it in an aquarium, and for the first time we have a chance to see
what it is like. We see that its body is almost elliptical in outline,
but with flat sides and shaped on the lower parts very much like a
boat. This form we see is such as to enable it to part the water as it
swims. We notice that its progress comes through the sculling motion of
its broad, flat tail.
=Face of a Fish.=--When we look at the sunfish from the front we see
that it has a sort of face, not unlike that of higher animals. The big
eyes, one on each side, stand out without eyelids, but the fish can
move them at will, so that once in a while he seems to wink. There
isn't much of a nose between the eyes, but the mouth is very evident,
and the fish opens and shuts it as it breathes. We soon see that it
breathes water, taking it in through the mouth and letting it flow over
the gills, and then out through the opening behind the gill-covers.
=How the Fish Breathes.=--If we take another fish--for we shall
not kill this one--we shall see that in its throat, behind the
mouth-cavity, there are four rib-like bones on each side, above the
beginning of the gullet. These are the gill-arches, and on each one
of them there is a pair of rows of red fringes called the gills. Into
each of these fringes runs a blood-vessel. As the water passes over it
the oxygen it contains is absorbed through the skin of the gill-fringe
into the blood, which thus becomes purified. In the same manner the
impurities of the blood pass out into the water, and go out through
the gill-openings behind. The fish needs to breathe just as we do,
though the apparatus of breathing is not the same. Just as the air
becomes loaded with impurities when many people breathe it, so does
the water in our jar or aquarium become foul if it is breathed over
and over again by fishes. When a fish finds the water bad he comes
to the surface to gulp air, but his gills are not well fitted to use
undissolved air as a substitute for that contained in water. The rush
of a stream through the air purifies the water, and so again does the
growth of water plants, for these in the sunshine absorb and break up
carbonic acid gas, and throw out oxygen into the water.
=Teeth of the Fish.=--On the inner side of the gill-arch we find some
little projections which serve as strainers to the water. These are
called gill-rakers. In our sunfish they are short and thick, seeming
not to amount to much but in a herring they are very long and numerous.
Behind the gills, at the opening of the gullet, are some roundish bones
armed with short, thick teeth. These are called pharyngeals. They form
a sort of jaws in the throat, and they are useful in helping the little
fish to crack shells. If we look at the mouth of our live fish, we
shall find that when it breathes or bites it moves the lower jaw very
much as a dog does. But it can move the upper jaw, too, a little, and
that by pushing it out in a queer fashion, as though it were thrust out
of a sheath and then drawn in. If we look at our dead fish, we shall
see that the upper jaw divides in the middle and has two bones on each
side. On one bone are rows of little teeth, while the other bone that
lies behind it has no teeth at all. The lower jaw has little teeth like
those of the upper jaw, and there is a patch of teeth on the roof of
the mouth also. In some sunfishes there are three little patches, the
vomer in the middle and the palatines on either side.
The tongue of the fish is flat and gristly. It cannot move it, scarce
even taste its food with it, nor can it use it for making a noise. The
unruly member of a fish is not its tongue, but its tail.
=How the Fish Sees.=--To come back to the fish's eye again. We say
that it has no eyelids, and so, if it ever goes to sleep, it must keep
its eyes wide open. The iris is brown or red. The pupil is round, and
if we could cut open the eye we should see that the crystalline lens
is almost a perfect sphere, much more convex than the lens in land
animals. We shall learn that this is necessary for the fish to see
under water. It takes a very convex lens or even one perfectly round
to form images from rays of light passing through the water, because
the lens is but little more dense than the water itself. This makes
the fish near-sighted. He cannot see clearly anything out of water or
at a distance. Thus he has learned that when, in water or out, he sees
anything moving quickly it is probably something dangerous, and the
thing for him to do is to swim away and hide as swiftly as possible.
In front of the eye are the nostrils, on each side a pair of openings.
But they lead not into tubes, but into a little cup lined with delicate
pink tissues and the branching nerves of smell. The organ of smell
in nearly all fishes is a closed sac, and the fish does not use the
nostrils at all in breathing. But they can indicate the presence of
anything in the water which is good to eat, and eating is about the
only thing a fish cares for.
=Color of the Fish.=--Behind the eye there are several bones on the
side of the head which are more or less distinct from the skull itself.
These are called membrane bones because they are formed of membrane
which has become bony by the deposition in it of salts of lime. One
of these is called the opercle, or gill-cover, and before it, forming
a right angle, is the preopercle, or false gill-cover. On our sunfish
we see that the opercle ends behind in a long and narrow flap, which
looks like an ear. This is black in color, with an edging of scarlet
as though a drop of blood had spread along its margin. When the fish
is in the water its back is dark greenish-looking, like the weeds and
the sticks in the bottom, so that we cannot see it very plainly. This
is the way the fish looks to the fishhawks or herons in the air above
it who may come to the stream to look for fish. Those fishes which
from above look most like the bottom can most readily hide and save
themselves. The under side of the sunfish is paler, and most fishes
have the belly white. Fishes with white bellies swim high in the water,
and the fishes who would catch them lie below. To the fish in the water
all outside the water looks white, and so the white-bellied fishes are
hard for other fishes to see, just as it is hard for us to see a white
rabbit bounding over the snow.
[Illustration: FIG. 3.--Common sunfish, _Eupomotis gibbosus_ (Linnæus).
Natural size. (From life by R. W. Shufeldt.)]
But to be known of his own kind is good for the sunfish, and we may
imagine that the black ear-flap with its scarlet edge helps his mate
and friends to find him out, where they swim on his own level near
the bottom. Such marks are called recognition-marks, and a great many
fishes have them, but we have no certain knowledge as to their actual
purpose.
We are sure that the ear-flap is not an ear, however. No fishes have
any external ear, all their hearing apparatus being buried in the
skull. They cannot hear very much: possibly a great jar or splash
in the water may reach them, but whenever they hear any noise they
swim off to a hiding-place, for any disturbance whatever in the water
must arouse a fish's anxiety. The color of the live sunfish is very
brilliant. Its body is covered with scales, hard and firm, making
a close coat of mail, overlapping one another like shingles on a
roof. Over these is a thin skin in which are set little globules of
bright-colored matter, green, brown, and black, with dashes of scarlet,
blue, and white as well. These give the fish its varied colors. Some
coloring matter is under the scales also, and this especially makes
the back darker than the lower parts. The bright colors of the sunfish
change with its surroundings or with its feelings. When it lies in wait
under a dark log its colors are very dark. When it rests above the
white sands it is very pale. When it is guarding its nest from some
meddling perch its red shades flash out as it stands with fins spread,
as though a water knight with lance at rest, looking its fiercest at
the intruder.
When the sunfish is taken out of the water its colors seem to fade.
In the aquarium it is generally paler, but it will sometimes brighten
up when another of its own species is placed beside it. A cause of
this may lie in the nervous control of the muscles at the base of the
scales. When the scales lie very flat the color has one appearance.
When they rise a little the shade of color seems to change. If you let
fall some ink-drops between two panes of glass, then spread them apart
or press them together, you will see changes in the color and size
of the spots. Of this nature is the apparent change in the colors of
fishes under different conditions. Where the fish feels at its best
the colors are the richest. There are some fishes, too, in which the
male grows very brilliant in the breeding season through the deposition
of red, white, black, or blue pigments, or coloring matter, on its
scales or on its head or fins, this pigment being absorbed when the
mating season is over. This is not true of the sunfish, who remains
just about the same at all seasons. The male and female are colored
alike and are not to be distinguished without dissection. If we examine
the scales, we shall find that these are marked with fine lines and
concentric striæ, and part of the apparent color is due to the effect
of the fine lines on the light. This gives the bluish lustre or sheen
which we can see in certain lights, although we shall find no real blue
pigment under it. The inner edge of each scale is usually scalloped
or crinkled, and the outer margin of most of them has little prickly
points which make the fish seem rough when we pass our hand along his
sides.
[Illustration: FIG. 4.--_Ozorthe dictyogramma_ (Herzenstein). A
Japanese blenny, from Hakodate: showing increased number of lateral
lines, a trait characteristic of many fishes of the north Pacific.]
=The Lateral Line.=--Along the side of the fish is a line of peculiar
scales which runs from the head to the tail. This is called the lateral
line. If we examine it carefully, we shall see that each scale has a
tube from which exudes a watery or mucous fluid. Behind these tubes are
nerves, and although not much is known of the function of the tubes,
we can be sure that in some degree the lateral line is a sense-organ,
perhaps aiding the fish to feel sound-waves or other disturbances in
the water.
=The Fins of the Fish.=--The fish moves itself and directs its
course in the water by means of its fins. These are made up of stiff
or flexible rods growing out from the body and joined together by
membrane. There are two kinds of these rays or rods in the fins. One
sort is without joints or branches, tapering to a sharp point. The rays
thus fashioned are called spines, and they are in the sunfish stiff
and sharp-pointed. The others, known as soft rays, are made up of
many little joints, and most of them branch and spread out brush-like
at their tips. In the fin on the back the first ten of the rays are
spines, the rest are soft rays. In the fin under the tail there are
three spines, and in each fin at the breast there is one spine with
five soft rays. In the other fins all the rays are soft.
The fin on the back is called the dorsal fin, the fin at the end of
the tail is the caudal fin, the fin just in front of this on the
lower side is the anal fin. The fins, one on each side, just behind
the gill-openings are called the pectoral fins. These correspond to
the arms of man, the wings of birds, or the fore legs of a turtle or
lizard. Below these, corresponding to the hind legs, is the pair of
fins known as the ventral fins. If we examine the bones behind the
gill-openings to which the pectoral fins are attached, we shall find
that they correspond after a fashion to the shoulder-girdle of higher
animals. But the shoulder-bone in the sunfish is joined to the back
part of the skull, so that the fish has not any neck at all. In animals
with necks the bones at the shoulder are placed at some distance behind
the skull.
If we examine the legs of a fish, the ventral fins, we shall find
that, as in man, these are fastened to a bone inside called the
pelvis. But the pelvis in the sunfish is small and it is placed far
forward, so that it is joined to the tip of the "collar-bone" of the
shoulder-girdle and pelvis attached together. The caudal fin gives most
of the motion of a fish. The other fins are mostly used in maintaining
equilibrium and direction. The pectoral fins are almost constantly in
motion, and they may sometimes help in breathing by starting currents
outside which draw water over the gills.
=The Skeleton of the Fish.=--The skeleton of the fish, like that of
man, is made up of the skull, the back-bone, the limbs, and their
appendages. But in the fish the bones are relatively smaller, more
numerous, and not so firm. The front end of the vertebral column is
modified as a skull to contain the little brain which serves for all
a fish's activities. To the skull are attached the jaws, the membrane
bones, and the shoulder-girdle. The back-bone itself in the sunfish
is made of about twenty-four pieces, or vertebræ. Each of these has a
rounded central part, concave in front and behind. Above this is a
channel through which the great spinal cord passes, and above and below
are a certain number of processes or projecting points. To some of
these, through the medium of another set of sharp bones, the fins of
the back are attached. Along the sides of the body are the slender ribs.
=The Fish in Action.=--The fish is, like any other animal, a machine
to convert food into power. It devours other animals or plants,
assimilates their substance, takes it over into itself, and through its
movements uses up this substance again. The food of the sunfish is made
up of worms, insects, and little fishes. To seize these it uses its
mouth and teeth. To digest them it needs its alimentary canal, made of
the stomach with its glands and intestines. If we cut the fish open, we
shall find the stomach with its pyloric cæca, near it the large liver
with its gall-bladder, and on the other side the smaller spleen. After
the food is dissolved in the stomach and intestines the nutritious part
is taken up by the walls of the alimentary canal, whence it passes into
the blood.
The blood is made pure in the gills, as we have already seen. To send
it to the gills the fish has need of a little pumping-engine, and
this we shall find at work in the fish as in all higher animals. This
engine of stout muscle surrounding a cavity is called the heart. In
most fishes it is close behind the gills. It contains one auricle and
one ventricle only, not two of each as in man. The auricle receives
the impure blood from all parts of the body. It passes it on to the
ventricle, which, being thick-walled, is dark red in color. This passes
the blood by convulsive action, or heart-beating, on to the gills. From
these the blood is collected in arteries, and without again returning
to the heart it flows all through the body. The blood in the fish flows
sluggishly. The combustion of waste material goes on slowly, and so the
blood is not made hot as it is in the higher beasts and birds. Fishes
have relatively little blood; what there is is rather pale and cold and
has no swift current.
If we look about in the inside of a fish, we shall find close along the
lower side of the back-bone, covering the great artery, the dark red
kidneys. These strain out from the blood a certain class of impurities,
poisons made from nerve or muscle waste which cannot be burned away by
the oxygen of respiration.
=The Air-bladder.=--In the front part of the sunfish, just above
the stomach, is a closed sac, filled with air. This is called the
air-bladder, or swim-bladder. It helps the fish to maintain its place
in the water. In bottom fishes it is almost always small, while fishes
that rise and fall in the current generally have a large swim-bladder.
The gas inside it is secreted from the blood, for the sunfish has no
way of getting any air into it from the outside.
But the primal purpose of the air-bladder was not to serve as a float.
In very old-fashioned fishes it has a tube connecting it with the
throat, and instead of being an empty sac it is a true lung made up of
many lobes and parts and lined with little blood-vessels. Such fishes
as the garpike and the bowfin have lung-like air-bladders and gulp air
from the surface of the water.
In the very little sunfish, when he is just hatched, the air-bladder
has an air-duct, which, however, is soon lost, leaving only a closed
sac. From all this we know that the air-bladder is the remains of
what was once a lung, or additional arrangement for breathing. As the
gills furnish oxygen enough, the lung of the common fish has fallen
into disuse and thrifty Nature has used the parts and the space for
another and a very different purpose. This will serve to help us to
understand the swim-bladder and the way the fish came to acquire it as
a substitute for a lung.
=The Brain of the Fish.=--The movements of the fish, like those of
every other complex animal, are directed by a central nervous system,
of which the principal part is in the head and is known as the brain.
From the eye of the fish a large nerve goes to the brain to report
what is in sight. Other nerves go from the nostrils, the ears, the
skin, and every part which has any sort of capacity for feeling. These
nerves carry their messages inward, and when they reach the brain they
may be transformed into movement. The brain sends back messages to the
muscles, directing them to contract. Their contraction moves the fins,
and the fish is shoved along through the water. To scare the fish or to
attract it to its food or to its mate is about the whole range of the
effect that sight or touch has on the animal. These sensations changed
into movement constitute what is called reflex action, performance
without thinking of what is being done. With a boy, many familiar
actions may be equally reflex. The boy can also do many other things
"of his own accord," that is, by conscious effort. He can choose among
a great many possible actions. But a fish cannot. If he is scared, he
must swim away, and he has no way to stop himself. If he is hungry,
and most fishes are so all the time, he will spring at the bait. If
he is thirsty, he will gasp, and there is nothing else for him to do.
In other words, the activities of a fish are nearly all reflex, most
of them being suggested and immediately directed by the influence of
external things. Because its actions are all reflex the brain is very
small, very primitive, and very simple, nothing more being needed for
automatic movement. Small as the fish's skull-cavity is, the brain does
not half fill it.
[Illustration: FIG. 5.--Common Sunfish, _Eupomotis gibbosus_ (Linnæus).
Natural size. (From life by R. W. Shufeldt.)--Page 13.]
The vacant space about the little brain is filled with a fatty fluid
mass looking like white of egg, intended for its protection. Taking the
dead sunfish (for the live one we shall look after carefully, giving
him every day fresh water and a fresh worm or snail or bit of beef), if
we cut off the upper part of the skull we shall see the separate parts
of the brain, most of them lying in pairs, side by side, in the bottom
of the brain-cavity. The largest pair is near the middle of the length
of the brain, two nerve-masses (or ganglia), each one round and hollow.
If we turn these over, we shall see that the nerves of the eye run into
them. We know then that these nerve-masses receive the impressions of
sight, and so they are called optic lobes. In front of the optic lobes
are two smaller and more oblong nerve-masses. These constitute the
cerebrum. This is the thinking part of the brain, and in man and in
the higher animals it makes up the greater part of it, overlapping and
hiding the other ganglia. But the fish has not much need for thinking
and its fore-brain or cerebrum is very small. In front of these are
two small, slim projections, one going to each nostril. These are
the olfactory lobes which receive the sensation of smell. Behind the
optic lobes is a single small lobe, not divided into two. This is the
cerebellum and it has charge of certain powers of motion. Under the
cerebellum is the medulla, below which the spinal cord begins. The
rest of the spinal cord is threaded through the different vertebræ
back to the tail, and at each joint it sends out nerves of motion and
receives nerves of sense. Everything that is done by the fish, inside
or outside, receives the attention of the little branches of the great
nerve-cord.
=The Fish's Nest.=--The sunfish in the spawning time will build some
sort of a nest of stones on the bottom of the eddy, and then, when the
eggs are laid, the male with flashing eye and fins all spread will
defend the place with a good deal of spirit. All this we call instinct.
He fights as well the first time as the last. The pressure of the eggs
suggests nest-building to the female. The presence of the eggs tells
the male to defend them. But the facts of the nest-building and nest
protection are not very well understood, and any boy who can watch them
and describe them truly will be able to add something to science.