AN INTRODUCTION
TO THE
STUDY OF FISHES

BY

ALBERT C. L. G. GÜNTHER

M.A. M.D. Ph.D. F.R.S.

KEEPER OF THE ZOOLOGICAL DEPARTMENT IN THE BRITISH MUSEUM

Carpit aquas pinnis.

EDINBURGH
ADAM AND CHARLES BLACK
1880

[All rights reserved.]

Printed by R. & R. Clark, Edinburgh.

PREFACE.

The scope of the present work is to give in a concise form an account of the principal facts relating to the structure, classification, and life-history of Fishes. It is intended to meet the requirements of those who are desirous of studying the elements of Ichthyology; to serve as a book of reference to zoologists generally; and, finally, to supply those who, like travellers, have frequent opportunities of observing fishes, with a ready means of obtaining information. The article on “Ichthyology,” prepared by the late Sir J. Richardson for the eighth edition of the “Encyclopædia Britannica,” is the only publication which has hitherto partly satisfied such requirements; and when I undertook, some years ago, to revise, or rather rewrite that article for the new edition of that work, it occurred to me that I might at the same time prepare a Handbook of Ichthyology, whilst reserving for the article an abstract so condensed as to be adapted for the wants of the general reader.

From the general plan of the work I have only departed in those chapters which deal with the Geographical Distribution of Fishes. This is a subject which has never before been treated in a general and comprehensive manner, and seemed to demand particular attention. I have, therefore, thought it right to give nominal lists of the Faunæ, and the other details of fact on which I have based my conclusions, although all the necessary materials may be found in my “Catalogue of Fishes.”

A few references only to the numerous sources which were consulted on the subjects of Chapters 1–12, are inserted in the text; more not required by the beginner; he is introduced to a merely elementary knowledge of facts well known to the advanced student.

With regard to the illustrations, about twenty have been prepared after originals published by Cuvier, J. Müller, Owen, Traquair, Duméril, Cunningham, Hasse, Poey, Siebold, and Gegenbaur. A similar number, representing extinct fishes, have been taken, with the kind permission of the author, from Owen’s “Palæontology.” My best thanks are due also to the Committee of Publications of the Zoological Society, and to the Editors of the “Annals and Magazine of Natural History,” and of the “Journal des Museum Godeffroy,” for the loan of woodcuts illustrating some of my papers on South American fishes and on larval forms. The remainder of the illustrations (about three-fourths) are either original figures, or formed part of the article on ‘Ichthyology’ in the former edition of the “Encyclopædia Britannica.”

London, 3d October 1880.

CONTENTS.

SYSTEMATIC AND DESCRIPTIVE PART.

INTRODUCTORY REMARKS.

According to the views generally adopted at present, all those Vertebrate animals are referred to the Class of Fishes, which living in water, breathe air dissolved in water by means of gills or branchiæ; whose heart consists of a single ventricle and single atrium; whose limbs, if present, are modified into fins, supplemented by unpaired, median fins; and whose skin is either naked, or covered with scales or osseous plates or bucklers. With few exceptions fishes are oviparous. However, there are not a few members of this Class which show a modification of one or more of these characteristics, as we shall see hereafter, and which, nevertheless, cannot be separated from it. The distinction between the Class of Fishes and that of Batrachians is very slight indeed.

The branch of Zoology which treats of the internal and external structure of fishes, their mode of life, and their distribution in space and time, is termed Ichthyology.[1]

CHAPTER I.
HISTORY AND LITERATURE.

Aristotle.

The commencement of the history of Ichthyology coincides with that of Zoology generally. Aristotle (384–322 B.C.) had a perfect knowledge of the general structure of fishes, which he clearly discriminates from the Aquatic animals with lungs and mammæ, i.e. Cetaceans, and from the various groups of Aquatic Invertebrates. He says that “the special characteristics of the true fishes consist in the branchiæ and fins, the majority having four fins, but those of an elongate form, as the eels, having two only. Some, as the Muræna, lack the fins altogether. The Rays swim with their whole body, which is spread out. The branchiæ are sometimes furnished with an opercle, sometimes without one, as is the case in the cartilaginous fishes.... No fish has hairs or feathers; most are covered with scales, but some have a rough or smooth skin. The tongue is hard, often toothed; and sometimes so much adherent that it seems to be wanting. The eyes have no lids; nor are any ears or nostrils visible, for what takes the place of nostrils is a blind cavity. Nevertheless they have the senses of tasting, smelling, and hearing. All have blood. All scaly fishes are oviparous, but the cartilaginous fishes (with the exception of the Sea-devil, which Aristotle places along with them) are viviparous. All have a heart, liver, and gall-bladder; but kidneys and urinary bladder are absent. They vary much in the structure of their intestines: for whilst the mullet has a fleshy stomach like a bird, others have no stomachic dilatation. Pyloric coeca are close to the stomach, variable in number; there are even some, like the majority of the cartilaginous fishes, which have none whatever. Two bodies are situated along the spine, which have the function of testicles, and open towards the vent, and which are much enlarged in the spawning season. The scales become harder with age. Not being provided with lungs, they have no voice, but several can emit grunting sounds. They sleep like other animals. In the majority the females exceed the males in size; and in the Rays and Sharks the male is distinguished by an appendage on each side of the vent.”

Aristotle’s information on the habits of fishes, their migrations, mode and time of propagation, utility, is, as far as it has been tested, surprisingly correct. Unfortunately, only too often we lack the means of recognising the species of which he gives a description. His ideas of specific distinction were as vague as those of the fishermen whose nomenclature he adopted; it never occurred to him that such popular names are subject to change, or may be entirely lost with time, and the difficulty of deciphering his species is further increased by the circumstance that popular names are often applied by him to the same fish, or that different stages of growth are designated by distinct names. The number of fishes known to Aristotle seems to have been about 115, all of which are inhabitants of the Ægean Sea.

That one man should have discovered so many truths, and formed so sure a base for Zoology, is less surprising than the fact that for about eighteen centuries a science which seemed to offer particular attractions to men gifted with power of observation, was no farther advanced. Yet this is the case. Aristotle’s disciples, as well as his successors, remained satisfied to be his copiers or commentators, and to collect fabulous stories or vague notions. With very few exceptions (such as Ausonius, who wrote a small poem, in which he describes from his own observations the fishes of the Mosel) authors entirely abandoned original research. And it was not until about the middle of the sixteenth century that Ichthyology made a new step in advance by the appearance of Belon, Rondelet, and Salviani, who almost simultaneously published their grand works, by which the idea of species was established definitely and for all times.

Belon.

P. Belon travelled in the countries bordering on the eastern part of the Mediterranean, in the years 1547–50; he collected rich stores of positive knowledge, which he deposited in several works. The one most important for the progress of Ichthyology is that entitled “De aquatilibus libri duo” (Paris 1553; small 4to.) Belon knows about 110 fishes, of which he gives rude, but generally recognisable, figures. In his descriptions he pays regard to the classical as well as vernacular nomenclature, and states the outward characteristics, sometimes even the number of fin-rays, frequently also the most conspicuous anatomical peculiarities.

Although Belon but rarely gives definitions of the terms used by him, it is generally not very difficult to ascertain the limits which he intended to assign to each division of aquatic animals. He very properly divides them into such as are provided with blood, and into those without it: two divisions, called in modern language Vertebrate and Invertebrate aquatic animals. The former are classified by him according to sizes, the further subdivisions being based on the structure of the skeleton, mode of propagation, number of limbs, form of the body, and on the physical character of the localities inhabited by fishes. This classification is as follows:—

Salviani.

The work of the Roman ichthyologist, H. Salviani (1514–72), is characteristic of the high social position which the author held as the physician of three popes. Its title is “Aquatilium animalium historia” (Rom. 1554–57, fol.) It treats exclusively of the fishes of Italy. Ninety-two species are figured on seventy-six plates which, as regards artistic execution, are masterpieces of that period, although those specific characteristics which nowadays constitute the value of a zoological drawing, were entirely overlooked by the author or artist. No attempt is made at a natural classification, but the allied forms generally are placed in close proximity. The descriptions are quite equal to those given by Belon, entering much into the details of the economy and usefulness of the several species, and were evidently composed with the view of collecting in a readable form all that might prove of interest to the class of society in which the author moved. Salviani’s work is of a high standard, most remarkable for the age in which he lived. It could not fail to convey valuable instruction, and to render Ichthyology popular in the country to the fauna of which it was devoted, but it would not have advanced Ichthyology as science generally; and in this respect Salviani is not to be compared with Rondelet or Belon.

Rondelet.

G. Rondelet (1507–1557) had the great advantage over Belon in having received a medical education at Paris, and more especially in having gone through a complete course of instruction in anatomy as a pupil of Guentherus of Andernach. This is conspicuous throughout his works—“Libri de Piscibus marinis” (Lugd. 1554, fol.); and “Universæ aquatilium historiæ pars altera” (Lugd. 1555, fol.) Nevertheless they cannot be regarded as more than considerably enlarged editions of Belon’s work. For although he worked independently of the latter, and differs from him in numerous details, the system adopted by him is characterised by the same absence of the true principles of classification. Rondelet had a much more extensive knowledge of details. His work is almost entirely limited to European, and chiefly Mediterranean, forms, and comprises not less than 197 marine and 47 freshwater fishes. His descriptions are more complete and his figures much more accurate than those of Belon; and the specific account is preceded by introductory chapters in which he treats in a general manner on the distinctions, the external and internal parts, and on the economy of fishes. Like Belon, he had no conception of the various categories of classification—for instance, confounding throughout his work the terms “genus” and “species;” but he had intuitively a notion of what his successors called a “species,” and his principal object was to collect and give as much information as possible of such species.

For nearly a century the works of Belon and Rondelet remained the standard works of Ichthyology; but this science did not remain stationary during this period. The attention of naturalists was now directed to the products of foreign countries, especially the Spanish and Dutch possessions in the New World; and in Europe the establishment of anatomical schools and academies led to the careful investigation of the internal anatomy of the most remarkable European forms. Limited as these efforts were as to their scope, being directed either only to the fauna of some district, or to the dissection of a single species, they were sufficiently numerous to enlarge the views of naturalists, and to destroy that fatal dependency on preceding authorities which had continued to keep in bonds the minds of even such men as Rondelet and Belon.

W. Piso. G. Margrav.

The most noteworthy of those who were active in tropical countries are W. Piso and G. Margrav. They accompanied as physicians the Dutch Governor, Prince Moritz of Nassau, to Brazil (1637–44). Margrav especially studied the fauna of the country, and although he died before his return to Europe, his observations were published by his colleague, and embodied in a work “Historia naturalis Braziliæ” (Lugd. 1648, fol.), in which the fourth book treats of the fishes. He describes about 100 species, all of which had been previously unknown, in a manner far superior to that of his predecessors. The accompanying figures are not good, but nearly always recognisable, and giving a fair idea of the form of the fish. Margrav himself, with the aid of an artist, had made a most valuable collection of coloured drawings of the objects observed and described by him, but many years were allowed to pass before it was scientifically utilised by Bloch and others.

Anatomists, 1600–1700.

Of the men who left records of their anatomical researches, we may mention Borelli (1608–79), who wrote a work “De motu animalium” (Rom. 1680, 4to), in which he explained the mechanism of swimming, and the function of the air-bladder; M. Malpighi (1628–94), who examined the optic nerve of the sword-fish; the celebrated J. Swammerdam (1637–80), who described the intestines of numerous fishes; and J. Duverney (1648–1730), who entered into detailed researches of the organs of respiration.

A new era in the history of Ichthyology commences with Ray, Willughby, and Artedi, who were the first to recognise the true principles by which the natural affinities of animals should be determined. Their labours stand in so intimate a connection with each other that they represent only one stride in the progress of this science.

Ray and Willughby

J. Ray (born 1628 in Essex, died 1705), was the friend and guide of F. Willughby (1635–72). They had recognised that a thorough reform of the treatment of the vegetable and animal kingdoms had become necessary; that the only way of bringing order into the existing chaos was that of arranging the various forms with regard to their structure; that they must cease to be burdened with inapplicable passages and quotations of the ancient writers, and to perpetuate the erroneous or vague notions of their predecessors. They abandoned speculation, and adhered to facts only. One of the first results, and perhaps the most important, of their method was, that having recognised the “species” as such, they defined this term, and fixed it as the base, from which all sound zoological knowledge has to start.

Although they had divided their work thus that Ray attended to the plants principally, and Willughby to the animals, the “Historia piscium” (Oxford, 1686, fol.), which bears Willughby’s name on the titlepage, and was edited by Ray, is clearly their joint production. A great part of the observations contained in it were collected during their common journeys in Great Britain and on the Continent, and it is no exaggeration to say that at that time these two Englishmen knew the fishes of the Continent, especially those of Germany, better than any other Continental zoologist.

By the definition of fishes as animals with blood, breathing by gills, provided with a single ventricle of the heart, covered with scales or naked; the Cetaceans are excluded. Yet, at a later period Ray appears to have been afraid of so great an innovation as the separation of whales from fishes, and, therefore, he invented a definition of fish which comprises both. The fishes proper are then arranged in the first place according to the cartilaginous or osseous nature of the skeleton; further subdivisions being formed with regard to the general form of the body, the presence or absence of ventral fins, the soft or spinous structure of the dorsal rays, the number of dorsal fins, etc. Not less than 420 species are thus arranged and described, of which about 180 were known to the authors from autopsy: a comparatively small proportion, descriptions and figures still forming at that time in a great measure a substitute for collections and museums. With the increasing accumulation of forms the want of a fixed nomenclature is now more and more felt.

P. Artedi.

Peter Artedi would have been a great ichthyologist if Ray or Willughby had never preceded him. But he was fully conscious of the fact that both had prepared the way for him, and therefore he derived all possible advantages from their works. Born in 1705 in Sweden, he studied with Linnæus at Upsala; from an early period he devoted himself entirely to the study of fishes, and was engaged in the arrangement and description of the ichthyological collection of Seba, a wealthy Dutchman who had formed the then perhaps richest museum, when he was accidentally drowned in one of the canals of Amsterdam in the year 1734, at an age of twenty-nine years. His manuscripts were fortunately rescued by an Englishman, Cliffort, and edited by his early friend Linnæus.

The work is divided into the following parts:—

1. In the “Bibliotheca Ichthyologica” Artedi gives a very complete list of all preceding authors who have written on fishes, with a critical analysis of their works.

2. The “Philosophia Ichthyologica” is devoted to a description of the external and internal parts of fishes; Artedi fixes a precise terminology of all the various modifications of the organs, distinguishes between those characters which determine a genus and such as indicate a species or merely a variety; in fact he establishes the method and principles which subsequently have guided every systematic ichthyologist.

3. The “Genera Piscium” contains well-defined diagnoses of forty-five genera, for which he fixes an unchangeable nomenclature.

4. In the “Species Piscium” descriptions of seventy-two species, examined by himself, are given; descriptions which even now are models of exactitude and method.

5. Finally, in the “Synonymia Piscium” references to all previous authors are arranged for every species, very much in the same manner which is adopted in the systematic works of the present day.

Linnæus.

Artedi has been justly called the Father of Ichthyology. So perfect was his treatment of the subject, that even Linnæus could no more improve it, only modify and add to it; and as far as Ichthyology is concerned, Linnæus has scarcely done anything beyond applying binominal terms to the species properly described and classified by Artedi.

Artedi had divided the fishes proper into four orders, viz. Malacopterygii, Acanthopterygii, Branchiostegi, and Chondropterygii, of which the third only, according to our present knowledge, appears to be singularly heterogeneous, as it comprises Balistes, Ostracion, Cyclopterus, and Lophius. Linnæus, besides separating the Cetaceans entirely from the class of fishes (at least since the 10th edition of the “Systema Naturæ”) abandoned Artedi’s order of Branchiostegi, but substituted a scarcely more natural combination by joining it with Artedi’s Chondropterygians, under the name of “Amphibia nantes.”

His classification of the genera appears in the 12th edition of the “Systema,” thus—

Amphibia Nantes.

Spiraculis compositis.

• Petromyzon.
• Raia.
• Squalus.
• Chimæra.

Spiraculis solitariis.

• Lophius.
• Acipenser.
• Cyclopterus.
• Balistes.
• Ostracion.
• Tetrodon.
• Diodon.
• Centriscus.
• Syngnathus.
• Pegasus.

Pisces Apodes.

• Muræna.
• Gymnotus.
• Trichiurus.
• Anarhichas.
• Ammodytes.
• Ophidium.
• Stromateus.
• Xiphias.

Pisces Jugulares.

• Callionymus.
• Uranoscopus.
• Trachinus.
• Gadus.
• Blennius.

Pisces Thoracici.

• Cepola.
• Echeneis.
• Coryphæna.
• Gobius.
• Cottus.
• Scorpæna.
• Zeus.
• Pleuronectes.
• Chæetodon.
• Sparus.
• Labrus.
• Sciæna.
• Perca.
• Gasterosteus.
• Scomber.
• Mullus.
• Trigla.

Pisces Abdominales.

• Cobitis.
• Amia.
• Silurus.
• Teuthis.
• Loricaria.
• Salmo.
• Fistularia.
• Esox.
• Elops.
• Argentina.
• Atherina.
• Mugil.
• Mormyrus.
• Exocœtus.
• Polynemus.
• Clupea.
• Cyprinus.

Gronow and Klein.

Two contemporaries of Linnæus attempted a systematic arrangement of fishes; both had considerable opportunities for their study, especially in possessing extensive collections; but neither exercised any influence on the progress of Ichthyology. The one, L. T. Gronow, a German who resided in Holland, closely followed the arrangements proposed by Artedi and Linnæus, and increased the number of genera and species from the contents of his own museum. He published two works, “Museum Ichthyologicum” (Lugd. 1754–6, fol.), and “Zoophylacium” (Lugd. 1763–81, fol.); a posthumous work, containing numerous excellent descriptions of new forms was published by J. E. Gray in 1854 under the title of “Systema Ichthyologicum.” To Gronow also is due the invention of preparing flat skins of fishes in a dry state, and preserving them in the manner of a herbarium. The specimens thus prepared by him belong to the oldest which have been preserved down to our time.

Much less important are the ichthyological labours of J. T. Klein (1685–1759). They are embodied in five parts (Missus) of a work entitled “Historia naturalis piscium” (Sedæ, 1740–9, 4to.) He regarded a system merely as the means of recognising the various forms of animals, not as the expression of their natural affinities; and that method seemed to him to be the most perfect by which an animal could be most readily determined. He eschewed all reference to minute or anatomical characters. Hence his system is a series of the most unnatural combinations, and we cannot be surprised that Linnæus passed in silence over Klein’s labours.

Pupils and Successors of Linnæus

The works of Artedi and Linnæus excited fresh activity, more especially in Scandinavia, Holland, Germany, and England, such as has not been equalled in the history of biological science either before or after. Whilst some of the pupils and followers of Linnæus devoted themselves to an examination and study of the fauna of their native countries, others proceeded on voyages of discovery to foreign and distant countries. Of these latter the following may be specially mentioned:—O. Fabricius worked out the Fauna of Greenland, Kalm collected in North America, Hasselquist in Egypt and Palestine, Brünnich in the Mediterranean, Osbeck in Java and China, Thurnberg in Japan; Forskål examined and described the fishes of the Red Sea; Steller, Pallas, S. T. Gmelin, and Güldenstedt traversed nearly the whole of the Russian Empire in Europe and Asia. Others attached themselves as naturalists to the celebrated circumnavigators of the last century, like the two Forsters (father and son), and Solander, who accompanied Cook; Commerson, who travelled with Bougainville; and Sonnerat. Numerous new and startling forms were discovered by those men, and the foundation was laid of the knowledge of the geographical distribution of animals.

Of those who studied the fishes of their native country the most celebrated are Pennant (Great Britain), O. F. Müller (Denmark), Duhamel (France), Meidinger (Austria), Cornide (Spain), Parra (Cuba).

The materials brought together by those and other zoologists were so numerous that, not long after the death of Linnæus, the necessity was felt of collecting them in a compendious form. Several compilators undertook this task; they embodied the recent discoveries in new editions of Artedi’s and Linné’s classical works, but not possessing either a knowledge of the subject or any critical discernment, they only succeeded in covering those noble monuments under a mass of confused rubbish. For Ichthyology it was fortunate that two men at least, Bloch and Lacépède, made it a subject of long and original research.

M. E. Bloch.

Mark Eliezer Bloch, born in the year 1723 at Anspach in Germany, practised as a physician in Berlin; he had reached an age of fifty-six years when he commenced to write on ichthyological subjects. To commence at his age a work in which he intended not only to give full descriptions of the species known to him from specimens or drawings, but also to illustrate every species in a style truly magnificent for his time, was an undertaking of the execution of which an ordinary man would have despaired. Yet he accomplished not only this task, but even more, as we shall see hereafter.

His work consists of two divisions:—

1. “Oeconomische Naturgeschichte der Fische Deutschlands” (Berl. 1782–4, 4to. Plates in fol.)

2. “Naturgeschichte der auslændischen Fische” (Berl. 1785–95, 4to. Plates in fol.)

Bloch’s work is unique, and probably will for ever remain so. Although Cuvier fifty years later undertook a similar general work on fishes, the subject had then become too extensive to allow of an attempt of giving illustrations of all the species, or illustrations of a similar size and costliness.

The first division of the work, which is devoted to a description of the fishes of Germany, is entirely original, and based upon Bloch’s own observations. His descriptions as well as figures were made from nature, and are, with but few exceptions, still serviceable; many continue to be the best existing in literature.

Bloch was less fortunate and is much less reliable in his natural history of foreign fishes. For many of the species he had to rely on more or less incorrect drawings and descriptions of travellers; frequently, also, he was deceived as to the origin of specimens which he acquired by purchase. Hence his accounts contain numerous confusing errors which it would have been difficult to correct, if not nearly the whole of the materials on which his work is based had been preserved in the collections at Berlin.

After the completion of his Ichthyology Bloch occupied himself with systematic work. He prepared a general system of fishes, in which he arranged not only those described in his great work, but also those with which he had become acquainted afterwards from the descriptions of others. The work was ably edited and published after Bloch’s death by a philologist, J. G. Schneider, under the title “M. E. Blochii Systema ichthyologiæ iconibus ex. illustratum” (Berl. 1801, 8vo.) The number of species enumerated in it amounts to 1519. The system is based upon the number of the fins, the various orders being termed Hendecapterygii, Decapterygii, etc. We need not add that an artificial method like this led to the most unnatural combinations or severances.

Lacépède.

Bloch’s Ichthyology remained for many years the standard work, and, by the great number of excellent illustrations, proved a most useful guide to the student. But as regards originality of thought, Bloch was far surpassed by his contemporary, B. G. E. de Lacépède, born at Agen, in France, in 1756, a man of great and general erudition, who died as Professor of the Museum of Natural History of Paris in 1826.

Lacépède had to contend with great difficulties in the preparation of his “Histoire des Poissons” (Paris, 1798–1803, 4to, in 5 vols.), which was written during the most disturbed period of the French Revolution. A great part of it was composed whilst the author was separated from collections and books, and had to rely on his notes and manuscripts only. Even the works of Bloch and other contemporaneous authors remained unknown, or at least inaccessible, to him for a long time. Therefore we cannot be surprised that his work abounds in all those errors to which a compiler is subject. The same species not only appears under two and more distinct specific names, but it sometimes happens that the author understands so little the source from which he derives his information that the description is referred to one genus and the accompanying figure to another. The names of genera are unduly multiplied; and the figures with which the work is illustrated are far inferior to those of Bloch. Thus the influence of Lacépède on the progress of Ichthyology was infinitely less than that of his fellow-labourer; and the labour caused to his successors by correcting the numerous errors into which he has fallen, probably outweighs the assistance which they derived from his work.

Anatomists.

The work of the principal cultivators of Ichthyology in the period between Ray and Lacépède was chiefly systematic and descriptive, but also the internal organisation of fishes received attention from more than one great anatomist. Haller, Camper, and Hunter, examined the nervous system and organs of sense; and more especially Alexander Monro (the son) published a classical work, “The Structure and Physiology of Fishes explained and compared with those of Man and other Animals” (Edinb. 1785, fol.) The electric organs of fishes (Torpedo and Gymnotus) were examined by Réaumur, Allamand, Bancroft, Walsh, and still more exactly by J. Hunter. The mystery of the propagation of the Eel called forth a large number of essays, and even the artificial propagation of Salmonidæ was known and practised by Gleditsch (1764).

Faunists.

Bloch and Lacépède’s works were almost immediately succeeded by the labours of Cuvier, but his early publications were of necessity tentative, preliminary, and fragmentary, so that a short period elapsed before the spirit infused by this great anatomist into Ichthyology could exercise its influence on all workers in this field. Several of such antecuvierian works must be mentioned on account of their importance to our knowledge of certain Faunas: the “Descriptions and Figures of Two Hundred Fishes collected at Vizagapatam on the coast of Coromandel” (Lond. 1803; 2 vols. in fol.), by Patrick Russel; and “An Account of the Fishes found in the River Ganges and its branches” (Edinb. 1822; 2 vols. in 4to), by F. Hamilton (formerly Buchanan)—works distinguished by a greater accuracy of their drawings (especially in the latter), than was ever attained before. A “Natural History of British Fishes” was published by E. Donovan (Lond. 8vo, 1802–8); and the Mediterranean Fauna formed the study of the lifetime of A. Risso (“Ichthyologie de Nice.” Paris, 1810, 8vo; and “Histoire naturelle de l’Europe Meridionale.” Paris, 1827, 8vo). A slight beginning in the description of the fishes of the United States was made by S. L. Mitchell, who published, besides various papers, a “Memoir on the Ichthyology of New York,” in 1815.[2]

G. Cuvier.

G. Cuvier did not occupy himself with the study of fishes merely because this class formed part of the “Règne animal,” but he devoted himself to it with particular predilection. The investigation of their anatomy, and especially of their skeleton, was taken up by him at an early period, and continued until he had succeeded in completing so perfect a framework of the system of the whole class that his immediate successors could content themselves with filling up those details for which their master had no leisure. Indefatigable in examining all the external and internal characters of the fishes of a rich collection, he ascertained the natural affinities of the infinite variety of fishes, and accurately defined the divisions, orders, families, and genera of the class, as they appear in the various editions of the “Règne animal.” His industry equalled his genius: he opened connections with almost every accessible part of the globe; not only French travellers and naturalists, but also Germans, Englishmen, Americans, rivalled one another to assist him with collections; and for many years the Muséum of the Jardin des Plantes was the centre where all ichthyological treasures were deposited. Thus Cuvier brought together a collection the like of which had never been seen before, and which, as it contains all the materials on which his labours were based, must still be considered to be the most important. Soon after the year 1820, Cuvier, assisted by one of his pupils, A. Valenciennes, commenced his great work on fishes, “Histoire naturelles des Poissons,” of which the first volume appeared in 1828. The earlier volumes, in which Cuvier himself took his share, bear evidence of the freshness and love with which both authors devoted themselves to their task. After Cuvier’s death in 1832 the work was left entirely in the hands of Valenciennes, whose energy and interest gradually slackened, to rise to the old standard in some parts only, as, for instance, in the treatise on the Herring. He left the work unfinished with the twenty-second volume (1848), which treats of the Salmonoids. Yet, incomplete as it is, it is indispensable to the student.

There exist several editions of the work, which, however, have the same text. One, printed in 8vo, with coloured or plain figures, is the one in common use among ichthyologists. A more luxurious edition in 4to has a different pagination, and therefore is most inconvenient to use.

As mentioned above, the various parts of the work are very unequally worked out. Many of the species are described in so masterly a manner that a greater excellency of method can hardly be conceived. The history of the literature of these species is entered into with minuteness and critical discernment; but in the later volumes, numerous species are introduced into the system without any description, or with a few words only, comparing a species with one or more of its congeners. Cuvier himself, at a late period of his life, seems to have grown indifferent as to the exact definition of his species: a failing commonly observed among Zoologists when attention to descriptive details becomes to them a tedious task. What is more surprising is, that a man of his anatomical and physiological knowledge should have overlooked the fact that secondary sexual characters are developed in fishes as in any other class of animals, and that fishes undergo great changes during growth; and, consequently, that he described almost all such sexual forms and different stages of growth under distinct specific and even generic names.

The system finally adopted by Cuvier is the following:—

A. Poissons Osseux.

I.—A BRANCHIES EN PEIGNES OU EN LAMES.

1. A MÂCHOIRE SUPÉRIEURE LIBRE.

a. Acanthoptérygiens.

• Percoïdes.
• Polynèmes.
• Mulles.
• Joues cuirassées.
• Scienoïdes.
• Sparoïdes.
• Chétodonoïdes.
• Scomberoïdes.
• Muges.
• Branchies labyrinthiques.
• Lophioïdes.
• Gobioïdes.
• Labroïdes.

b. Malacoptérygiens.

Abdominaux.

• Cyprinoïdes.
• Siluroïdes.
• Salmonoïdes.
• Clupeoïdes.
• Lucioïdes.

Subbrachiens.

• Sparoïdes.
• Pleuronectes.
• Discoboles.

Apodes.

• Murenoïdes.

2. A MÂCHOIRE SUPÉRIEURE FIXÉE.

• Sclérodermes.
• Gymnodontes.

II. A BRANCHIES EN FORME DE HOUPPES.

• Lophobranches.

B. Cartilagineux ou Chondroptérygiens.

• Sturioniens.
• Plagiostomes.
• Cyclostomes.

We have to compare this system with that of Linnæus if we wish to measure the gigantic stride Ichthyology has made during the intervening period of seventy years. The various characters employed for classification have been examined throughout the whole class, and their relative importance has been duly weighed and understood. Though Linnæus had formed a category of “Amphibia nantes” for fishes with a cartilaginous skeleton, which should coincide with Cuvier’s “Poissons Cartilagineux,” he had failed to understand the very nature of cartilage, apparently comprising by this term any skeletal framework of less firmity than ordinary bone. Hence he considered Lophius, Cyclopterus, Syngnathus to be cartilaginous fishes. Adopting the position and development of the ventral fins as a highly important character, he was obliged to associate fishes with rudimentary and inconspicuous ventral fins, like Trichiurus, Xiphias, etc., with the true Eels. The important category of a “family” appears now in Cuvier’s system fully established as that intermediate between genus and order. Important changes in Cuvier’s system have been made and proposed by his successors, but in the main it is still that of the present day.

Cuvier had extended his researches beyond the living forms, into the field of palæontology; he was the first to observe the close resemblance of the scales of the fossil Palæoniscus to those of the living Polypterus and Lepidosteus, the prolongation and identity of structure of the upper caudal lobe in Palæoniscus and the Sturgeons, the presence of peculiar “fulcra” on the anterior margin of the dorsal fin in Palæoniscus and Lepidosteus: inferring from these facts that that fossil genus was allied either to the Sturgeons or to Lepidosteus. But it did not occur to him that there was a close relationship between those recent fishes. Lepidosteus and, with it, the fossil genus remained in his system a member of the order of Malacopterygii abdominales.

It was left to L. Agassiz (born 1807, died 1873) to point out the importance of the character of the structure of the scales, and to open a path towards the knowledge of a whole new sub-class of fishes, the Ganoidei.

Impressed with the fact that the peculiar scales of Polypterus and Lepidosteus are common to all fossil osseous fishes down to the chalk, he takes the structure of the scales generally as the base for an ichthyological system, and distinguishes four orders:—

1. Placoids.—Without scales proper, but with scales of enamel, sometimes large, sometimes small and reduced to mere points (Rays, Sharks, and Cyclostomi, with the fossil Hybodontes).

2. Ganoids.—With angular bony scales, covered with a thick stratum of enamel: to this order belong the fossil Lepidoides, Sauroides, Pycnodontes, and Coelacanthi; the recent Polypterus, Lepidosteus, Sclerodermi, Gymnodontes, Lophobranches, and Siluroides; also the Sturgeons.

3. Ctenoids.—With rough scales, which have their free margins denticulated: Chætodontidæ, Pleuronectidæ, Percidæ, Polyacanthi, Sciænidæ, Sparidæ, Scorpænidæ, Aulostomi.

4. Cycloids.—With smooth scales, the hind margin of which lacks denticulation: Labridæ, Mugilidæ, Scombridæ, Gadoidei, Gobiidæ, Murænidæ, Lucioidei, Salmonidæ, Clupeidæ, Cyprinidæ.

We have no hesitation in affirming that if Agassiz had had an opportunity of acquiring a more extensive and intimate knowledge of existing fishes before his energies were absorbed in the study of their fossil remains, he himself would have recognised the artificial character of his classification. The distinctions between cycloid and ctenoid scales, between placoid and ganoid fishes are vague, and can hardly be maintained. As far as the living and post-cretacean forms are concerned, the vantage-ground gained by Cuvier was abandoned by him; and therefore his system could never supersede that of his predecessors, and finally shared the fate of every classification based on the modifications of one organ only. But Agassiz has the merit of having opened an immense new field of research by his study of the infinite variety of fossil forms. In his principal work, “Recherches sur les Poissons fossiles,” (Neuchatel, 1833–43, 4to, atlas in fol.), he placed them before the world arranged in a methodical manner, with excellent descriptions and illustrations. His power of discernment and penetration in determining even the most fragmentary remains is truly astonishing; and if his order of Ganoids is an assemblage of forms very different from that as it is circumscribed now, he was at any rate the first who recognised that such an order of fishes exists.

J. Müller.

The discoverer of the Ganoidei was succeeded by their explorer, Johannes Müller (born 1801, died 1858). In his classical memoir “Ueber den Bau und die Grenzen der Ganoiden” (Berlin, 1846; 4to), he showed that the Ganoids differed from all the other osseous fishes, and agreed with the Plagiostomes, in the structure of their heart. By this primary character, all heterogeneous elements, as Siluroids, Osteoglossidæ, etc., were eliminated from the order as understood by Agassiz. On the other hand, he did not recognise the affinity of Lepidosiren to the Ganoids, but established for it a distinct sub-class, Dipnoi, which he placed at the opposite end of the system. By his researches into the anatomy of the Lampreys and Amphioxus, their typical distinctness from other cartilaginous fishes was proved; they became the types of two other sub-classes, Cyclostomi and Leptocardii.

Müller proposed several other not unimportant modifications of the Cuvierian system; and although all cannot be maintained as the most natural arrangements, yet his researches have given us a much more complete knowledge of the organisation of the Teleosteous fishes, and later enquiries have shown that, on the whole, the combinations proposed by him require only some further modification and another definition to render them perfectly natural.

Under the name of Pharyngognathi he combined fishes with the lower pharyngeals coalesced into one bone, viz. the Labroids, Chromides, and Scombresoces. The association of the third family with the two former seemed to himself a somewhat arbitrary proceeding; and it had to be abandoned again, when a number of fishes which cannot be separated from the Acanthopterygians, were found to possess the same united pharyngeals.

A more natural combination is the union of the Cod-fishes with the Flat-fishes into the order Anacanthini. Flat-fishes are in fact nothing but asymmetrical Cod-fishes. Müller separates them from the remaining Malacopterygians by the absence of a connecting duct between the air-bladder and oesophagus. However, it must be admitted that the examination of those fishes, and especially of the young stages, is not complete enough to raise the question beyond every doubt, whether the presence or absence of that duct is an absolutely distinctive character between Anacanths and Malacopterygians.

Many of the families established by Cuvier were reexamined and better defined by Müller, as may be seen from the following outline of his system:—

Sub-classis I.—Dipnoi.

Ordo I.—Sirenoidei.

• Fam. 1. Sirenoidei.

Sub-classis II.—Teleostei.

Ordo I.—Acanthopteri.

• Fam. 1. Percoidei.
• „ 2. Cataphracti.
• „ 3. Sparoidei.
• „ 4. Sciænoidei.
• „ 5. Labyrinthiformes.
• „ 6. Mugiloidei.
• „ 7. Notacanthini.
• „ 8. Scomberoidei.
• „ 9. Squamipennes.
• „ 10. Taenioidei.
• „ 11. Gobioidei.
• „ 12. Blennioidei.
• „ 13. Pediculati.
• „ 14. Theutyes.
• „ 15. Fistulares.

Ordo II.—Anacanthini.

Sub-ordo I.—Anacanthini sub-brachii.

• Fam. 1. Gadoidei.
• „ 2. Pleuronectides.

Sub-ordo II.—Anacanthini apodes.

• Fam. 1. Ophidini.

Ordo III.—Pharyngognathi.

Sub-ordo I.—Pharyngognathi acanthopterygii.

• Fam. 1. Labroidei cycloidei.
• „ 2. Labroidei ctenoidei.
• „ 3. Chromides.

Sub-ordo II.—Pharyngognathi malacopterygii.

• Fam. 1. Scomberesoces.

Ordo IV.—Physostomi.

Sub-ordo I.—Physostomi abdominales.

• Fam. 1. Siluroidei.
• „ 2. Cyprinoidei.
• „ 3. Characini.
• „ 4. Cyprinodontes.
• „ 5. Mormyri.
• „ 6. Esoces.
• „ 7. Galaxiæ.
• „ 8. Salmones.
• „ 9. Scopelini.
• „ 10. Clupeidæ.
• „ 11. Heteropygii.

Sub-ordo II.—Physostomi apodes s. anguillares.

• Fam. 12. Murænoidei.
• „ 13. Gymnotini.
• „ 14. Symbranchii.

Ordo V.—Plectognathi.

• Fam. 1. Balistini.
• „ 2. Ostraciones.
• „ 3. Gymnodontes.

Ordo VI.—Lophobranchii.

• Fam. 1. Lophobranchi.

Sub-classis III.—Ganoidei.

Ordo I.—Holostei.

• Fam. 1. Lepidosteini.
• „ 2. Polypterini.

Ordo II.—Chondrostei.

• Fam. 1. Acipenserini,
• „ 2. Spatulariæ.

Sub-classis IV.—Elasmobranchi s. Selachii.

Ordo I.—Plagiostomi.

Sub-ordo I.—Squalidæ.

• Fam. 1. Scyllia.
• „ 2. Nyctitantes.
• „ 3. Lamnoidei.
• „ 4. Alopeciæ.
• „ 5. Cestraciones.
• „ 6. Rhinodontes.
• „ 7. Notidani.
• „ 8. Spinaces.
• „ 9. Scymnoidei.
• „ 10. Squatinæ.

Sub-ordo II.—Rajidæ.

• Fam. 11. Squatinorajæ.
• „ 12. Torpedines.
• „ 13. Rajæ.
• „ 14. Trygones.
• „ 15. Myliobatides.
• „ 16. Cephalopteræ.

Ordo II.—Holocephali.

• Fam. 1. Chimaeræ.

Sub-classis V.—Marsipobranchii s. Cyclostomi.

Ordo I.—Hyperoartii.

• Fam. 1. Petromyzonini.

Ordo II.—Hyperotreti.

• Fam. 1. Myxinoidei.

Sub-classis VI.—Leptocardii.

Ordo I.—Amphioxini.

• Fam. 1. Amphioxini.

Discovery of Ceratodus.

The discovery (in the year 1871) of a living representative of a genus hitherto believed to be long extinct, Ceratodus, threw a new light on the affinities of Fishes. The author who had the good fortune of examining this fish, was enabled to show that, on the one hand, it was a form most closely allied to Lepidosiren; on the other, that it could not be separated from the Ganoid fishes, and therefore that also Lepidosiren was a Ganoid: a relation pointed at already by Huxley in a previous paper on “Devonian Fishes.” This discovery led to further considerations[3] of the relative characters of Müller’s sub-classes, and to the system which is followed in the present work.

Having followed the development of the ichthyological system down to the latest time, we have to retrace our steps to enumerate the most important contributions to Ichthyology which appeared contemporaneously with or subsequently to the publication of Cuvier and Valenciennes’s great work. As in other branches of Zoology, activity increased almost with every year; and for convenience’s sake we may arrange these works in three rubrics.

Recent Works.

I.—Voyages, Containing General Accounts of Zoological Collections.

A. French.

1. “Voyage autour du monde sur les Corvettes de S. M. l’Uranie et la Physicienne, sous le commandement de M. Freycinet. Zoologie: Poissons par Quoy et Gaimard.” (Paris, 1824, 4to, atlas fol.)

2. “Voyage de la Coquille. Zoologie par Lesson.” (Paris, 1826–30, 4to, atlas fol.)

3. “Voyage de l’Astrolabe, sous le commandement de M. J. Dumont d’Urville. Poissons par Quoy et Gaimard.” (Paris, 1834, 8vo, atlas fol.)

4. “Voyage au Pôle Sud par M. J. Dumont d’Urville. Poissons par Hombron et Jacquinot.” (Paris, 1853–4, 8vo, atlas fol.)

B. English.

1. “Voyage of H.M.S. Sulphur. Fishes by J. Richardson.” (Lond. 1844–5, 4to.)

2. “Voyage of H.M.S.S. Erebus and Terror. Fishes by J. Richardson.” (Lond. 1846. 4to.)

3. “Voyage of H.M.S. Beagle. Fishes by L. Jenyns.” (Lond. 1842, 4to.)

4. “Voyage of H.M.S. Challenger. Fishes by A. Günther.” (in course of publication).

C. German.

1. “Reise der österreichischen Fregatte Novara. Fische von R. Kner.” (Wien. 1865, 4to.)

II.—Faunae.

A. Great Britain.

1. R. Parnell, “The Natural History of the Fishes of the Firth of Forth.” (Edinb. 1838, 8vo.)

2. W. Yarrell, “A History of British Fishes.” (3d edit. Lond. 1859, 8vo.)

3. J. Couch, “A History of the Fishes of the British Islands.” (Lond. 1862–5, 8vo.)

B. Denmark and Scandinavia.

1. H. Kröyer, “Danmark’s Fiske.” (Kjöbnh. 1838–53, 8vo.)

2. S. Nilsson, “Skandinavisk Fauna.” (Vol. IV. Fiskarna. Lund. 1855, 8vo.)

3. Fries och Ekström, “Skandinavians Fiskar.” (Stockh. 1836, 4to, with excellent plates.)

C. Russia.

1. Nordmann, “Ichthyologie Pontique,” in “Voyage dans la Russie méridionale de Demidoff.” (Tom. iii. Paris, 1840, 8vo, atlas fol.)

D. Germany.

1. Heckel and Kner, “Die Süsswasser-fische der Oesterreichischen Monarchie.” (Leipz. 1858, 8vo.)

2. C. T. E. Siebold, “Die Süsswasser-fische von Mitteleuropa.” (Leipz. 1863, 8vo.)

E. Italy and Mediterranean.

1. Bonaparte, “Iconografia della Fauna Italica.” Tom. iii. Pesci. (Roma, 1832–41, fol.) (Incomplete.)

2. Costa, “Fauna del Regno di Napoli.” Pesci. (Napoli, 4to, about 1850.) (Incomplete.)

F. France.

1. E. Blanchard, “Les Poissons des eaux douces de la France.” (Paris, 1866, 8vo.)

G. Pyrenean Peninsula.

The freshwater Fish-fauna of Spain and Portugal was almost unknown, until F. Steindachner paid some visits to those countries for the purpose of exploring the principal rivers. His discoveries are described in several papers in the “Sitzungsberichte der Akademie zu Wien.” B. du Bocage and F. Capello contributed towards the knowledge of the marine fishes on the coast of Portugal. (“Jorn. Scienc. Acad. Lisb.”)

H. North America.

1. J. Richardson, “Fauna Boreali Americana.” Part III. Fishes. (Lond. 1836, 4to.) The species described in this work are nearly all from the British possessions in the North.

2. Dekay, “Zoology of New York.” Part IV. Fishes. (New York, 1842, 4to.)

3. “Reports of the United States Commission of Fish and Fisheries.” (5 vols. Washingt. 1873–79, 8vo. In progress. Contains most valuable information.)

Besides these works, numerous descriptions of North American freshwater fishes have been published in the Reports of the various U. S. Government expeditions, and in North American scientific journals, by Storer, Baird, Girard, W. O. Ayres, Cope, Jordan, Brown Goode, etc.; but a good general, and especially critical, account of the fishes of the United States is still a desideratum.

I.—Japan.

1. “Fauna Japonica.” Poissons par H. Schlegel. (Lugd. Bat. 1850, fol.)

J.—East Indies; Tropical parts of the Indian and Pacific Oceans.

1. E. Rüppell, “Atlas zu der Reise im Nördlichen Afrika.” (Frankf. 1828, fol.)

2. E. Rüppell, “Neue Wirbelthiere. Fische.” (Frankf. 1837, fol.)

These two works form the standard works for the student of the Fishes of the Red Sea, and are distinguished by a rare conscientiousness and faithfulness of the descriptions and figures; so that there is no other part of the tropical seas, with the fishes of which we are so intimately acquainted, as with those of the Red Sea. But these works have a still wider range of usefulness, in as much as only a small proportion of the fishes is limited to that area, the majority being distributed over the Indian Ocean into Polynesia. Rüppel’s works were supplemented by the two first of the following works:—

3. R. L. Playfair and A. Günther, “The Fishes of Zanzibar.” (Lond. 1866, 4to); and

4. C. B. Klunzinger, “Synopsis der Fische des Rothen Meers.” (Wien. 1870–1, 8vo.)

5. T. Cantor, “Catalogue of Malayan Fishes.” (Calcutta, 1850, 8vo.)

6. F. Day, “The Fishes of India.” (Lond. 1875, 4to, in progress); contains an account of the freshwater and marine species, and is not yet complete.

7. A. Günther, “Die Fische der Südsee.” (Hamburg, 4to; from 1873, in progress.)

Unsurpassed in activity, as regards the exploration of the fish fauna of the East Indian Archipelago, is P. Bleeker, a surgeon in the service of the Dutch East Indian Government (born 1819, died 1878), who, from the year 1840, for nearly thirty years, amassed immense collections of the fishes of the various islands, and described them in extremely numerous papers, published chiefly in the Journals of the Batavian Society. When his descriptions and the arrangement of his materials evoked some criticism, it must be remembered that, at the time when he commenced his labours, and for many years afterwards, he stood alone, without the aid of a previously named collection on which to base his first researches, and without other works but that of Cuvier and Valenciennes. He had to create for himself a method of distinguishing species and of describing them; and afterwards it would have been difficult for him to abandon his original method and the principles by which he had been guided for so many years. His desire of giving a new name to every individual, to every small assemblage of species wherever practicable, or of changing an old name, detracts not a little from the satisfaction with which his works would be used otherwise. It is also surprising that a man with his anatomical knowledge and unusual facilities should have been satisfied with the merely external examination of the specimens. But none of his numerous articles contain anything relating to the anatomy, physiology, or habits of the fishes which came under his notice; hence his attempts at systematic arrangement are very far from indicating an advance in Ichthyology.

Soon after his return to Europe (1860) Bleeker commenced to collect the final results of his labours in a grand work, illustrated by coloured plates, “Atlas Ichthyologique des Indes Orientales Néerlandaises.” (Amsterd. fol. 1862); the publication of which was interrupted by the author’s death in 1878.

K.—Africa.

1. A. Günther, “The Fishes of the Nile” in Petherick’s “Travels in Central Africa.” (Lond. 1869, 8vo.)

2. W. Peters, “Naturwissenschaftliche Reise nach Mossambique. IV. Flussfische.” (Berl. 1868, 4to.)

L.—West Indies and South America.

1. L. Agassiz, “Selecta genera et species Piscium, quæ in itinere per Brasiliam, collegit J. B. de Spix.” (Monach. 1829, fol.)

2. F. de Castlenau, “Animaux nouveaux ou rares, recueillis pendant l’expedition dans les parties centrales de l’Amérique du Sud. Poissons.” (Paris, 1855, 4to.)

3. A. Günther, “An account of the Fishes of the States of Central America.” (In Trans. Zool. Soc. 1868.)

4. L. Vaillant and F. Bocourt, “Mission scientifique au Mexique et dans l’Amérique centrale. Poissons.” (Paris, 1874, 4to.) (In progress.)

F. Poey, the celebrated naturalist of Havannah, devoted many years of study to the Fishes of Cuba, His papers and memoirs are published partly in two periodicals, issued by himself, under the title of “Memorias sobre la Historia natural de la Isle de Cuba” (from 1851), and “Repertorio Fisico-natural de la Isla de Cuba” (from 1865), partly in North American scientific journals. And, finally, F. Steindachner has published many contributions, accompanied by excellent figures, to our knowledge of the Fishes of Central and South America.

M.—New Zealand.

1. F. W. Hutton and J. Hector, “Fishes of New Zealand.” (Wellingt. 1872, 8vo.)

N.—Arctic Regions.

1. G. Lütken, “A revised Catalogue of the Fishes of Greenland,” in “Manual of the Natural History, Geology, and Physics of Greenland.” (Lond. 1875, 8vo.) Although only a nominal list, this catalogue is useful, as it contains references to all the principal works in which Arctic fishes have been described. The fishes of Spitzbergen were examined by A. J. Malmgren (1865).

III.—Anatomical Works.

The number of authors who worked on the anatomy of fishes is almost as great as that of faunists; and we should go beyond the limits of the present work if we mentioned more than the most prominent and successful. M. H. Rathke, J. Müller, J. Hyrtl, and H. Stannius left scarcely any organ unexamined, and their researches had a direct bearing either on the relation of the class of fishes to the other vertebrates, or on the systematic arrangement of the fishes themselves. E. E. von Baer, F. de Filippi, C. Vogt, W. His, W. K. Parker, and F. M. Balfour worked at their embryology; A. Kölliker and G. Pouchet at their histology. The osteology was specially treated by G. Bakker, F. C. Rosenthal, L. Agassiz, and C. Gegenbaur; the nervous system by Gottsche, Philipeaux, Stannius, L. de Sanctis, L. Stieda, Baudelot and Miclucho-Maclay; the organ of hearing by E. H. Weber, C. Hasse, and G. Retzius. The electric fishes were examined by E. Geoffroy, C. Matteuci, P. Pacini, T. Bilharz, and Max Schultze. The development and metamorphosis of the Lamperns was made the subject of research by H. Müller, M. Schultze, and P. Owsjannikow; Müller’s examination of Branchiostoma was continued by J. Marcusen, A. Kovalevsky, L. Stieda, W. Müller, C. Hasse, T. Huxley, and F. M. Balfour. The most comprehensive accounts of the anatomy of fishes are contained in the following works:—

1. H. Stannius, “Zootomic der Fische,” 2d edit. (Berl. 1854, 8vo.)

2. R. Owen, “Anatomy of Vertebrates,” vol. i. (Lond. 1866, 8vo.)

3. R. Owen, “Lectures on the Comparative Anatomy and Physiology of the Vertebrate Animals.” Part I. Fishes. (Lond. 1846, 8vo.)

4. T. Huxley, “A Manual of the Anatomy of Vertebrated Animals.” (Lond. 1871, 16mo.)

Latest Systematic Works.

It has been mentioned above that the great work of Cuvier and Valenciennes had been left incomplete. Several authors, therefore, supplied detailed accounts of the orders omitted in that work. Müller and Henle published an account of the Plagiostomes, and Kaup of the Murænidæ and Lophobranchii. A. Duméril, finally, commenced an “Histoire naturelle des Poissons ou Ichthyologie générale,” of which, however, two volumes only appeared, containing a complete account of the “Plagiostomes” (Paris, 1865, 8vo.), and of the “Ganoids and Lophobranchs.” (Paris, 1870, 8vo.)

So great an activity had prevailed in Ichthyology since the publication of the “Histoire naturelle” by Cuvier and Valenciennes, and the results of the manifold enquiries were scattered over such a multitude of publications, that it became imperative to collect again all these materials in one comprehensive work. This was done in the “Catalogue of Fishes,” published by the Trustees of the British Museum, in eight volumes (Lond. 1859-70). Beside the species previously described many new forms were added, the number total of species referred to in those volumes amounting to 8525. As regards the systematic arrangement—Müller’s system was adopted in the main, but the definition of the families is much modified. This, however, need not be further entered into here, and will become sufficiently apparent in the subsequent parts of the present work.

Fig. 1.—Lower aspect of head of Raia lemprieri.

CHAPTER II.
TOPOGRAPHICAL DESCRIPTION OF THE EXTERNAL PARTS OF FISHES.

Form of the body.

In the body of a fish four parts are distinguished: the head, trunk, tail, and the fins; the boundary between the first and second being generally indicated by the gill-opening, and that between the second and third by the vent. The form of the body and the relative proportions of those principal parts are subject to much variation, such as is not found in any other class of Vertebrates. In fishes which are endowed with the power of steady and more or less rapid locomotion, a deviation from that form of body, which we observe in a perch, carp, or mackerel, is never excessive. The body forms a simple, equally-formed wedge, compressed or slightly rounded, well fitted for cleaving the water. In fishes which are in the habit of moving on the bottom, the whole body, or at least the head, is vertically depressed and flattened; the head may be so enormously enlarged that the trunk and tail appear merely as an appendage. In one family of fishes, the Pleuronectidæ or Flat-fishes, the body is compressed into a thin disk; they swim and move on one side only, which remains constantly directed towards the bottom, a peculiarity by which the symmetry of all parts of the body has been affected. A lateral compression of the body, in conjunction with a lengthening of the vertical and a shortening of the longitudinal axis, we find in fishes moving comparatively slowly through the water, and able to remain (as it were) suspended in it. This deviation from the typical form may proceed so far that the vertical axis greatly exceeds the longitudinal in length; generally all the parts of the body participate in this form, but in one kind of fish (the Sun-fish or Orthagoriscus) it is chiefly the tail which has been shortened, and reduced so much as to present the appearance of being cut off. An excessive lengthening of the longitudinal axis, with a shortening of the vertical, occurs in Eels and eel-like fishes, and in the so-called Band-fishes. They are bottom-fish, capable of insinuating themselves into narrow crevices and holes. The form of the body of these long fish is either cylindrical, snake-like, as in the Eels and many Cod-fishes, or strongly compressed as in the Band-fishes (Trichiurus, Regalecus, etc.) It is chiefly the tail which is lengthened, but frequently the head and trunk participate more or less in this form. Every possible variation occurs between these and other principal types of form. The old ichthyologists, even down to Linnæus, depended in great measure on them for classification; but although often the same form of body obtains in the same group of fishes, similarity of form by no means indicates natural affinity; it only indicates similitude of habits and mode of life.

Eye.

The external parts of the Head.—The Eye divides the head into the ante-orbital and post-orbital portion. In most fishes, especially in those with a compressed head, it is situated on the side and in the anterior half of the length of the head; in many, chiefly those with a depressed head, it is directed upwards, and sometimes situated quite at the upper side; in very few, the eyes look obliquely downwards. In the Flat-fishes both eyes are on the same side of the head, either the right or the left, always on that which is directed towards the light, and coloured.

Fishes in general, compared with other Vertebrata, have large eyes. Sometimes these organs are enormously enlarged, their great size indicating that the fish is either nocturnal, or lives at a depth to which only a part of the sun’s rays penetrate. On the other hand, small eyes occur in fishes inhabiting muddy places, or great depths to which scarcely any light descends, or in fishes in which the want of an organ of sight is compensated by the development of other organs of sense. In a few fishes, more particularly in those inhabiting caves or the greatest depths of the ocean, the eyes have become quite rudimentary and hidden under the skin.

Snout.

In the ante-orbital portion of the head, or the Snout, are situated the mouth and the nostrils.

Mouth.

The Mouth is formed by the intermaxillary and maxillary bones, or by the intermaxillary only in the upper jaw, and by the mandibulary bone in the lower. These bones are either bare or covered by integument, to which frequently labial folds or lips are added. As regards form, the mouth offers as many variations as the body itself, in accordance with the nature of the food, and the mode of feeding. It may be narrow, or extremely wide and cleft to nearly the hind margin of the head; it may be semi-elliptical, semicircular, or straight in a transverse line; it may be quite in front of the snout (anterior), or at its upper surface (superior), or at its lower (inferior), or extending along each side (lateral); sometimes it is subcircular, organised for sucking. The jaws of some fishes are modified into a special weapon of attack (Sword-fish, Saw-fish); in fact, throughout the whole class of fishes the jaws are the only organ specialised for the purpose of attacking; weapons on other parts of the body are purely defensive.

Both jaws may be provided with skinny appendages, barbels, which, if developed and movable, are sensitive organs of touch.

Nostrils.

In the majority of fishes the Nostrils are a double opening on each side of the upper surface of the snout; the openings of each side being more or less close together. They lead into a shallow groove; and only in one family (the Myxinoids) perforate the palate. In this family, as well as in the Lampreys, the nasal aperture is single. In many Eels the openings are lateral, the lower perforating the upper lip. In the Sharks and Rays (Fig. [1], p. 34) they are at the lower surface of the snout, and more or less confluent; and, finally, in the Dipnoi and other Ganoids, one at least is within the labial boundary of the mouth.

The space across the forehead, between the orbits, is called the interorbital space; that below the orbit, the infraorbital or sub-orbital region.

Gill-cover.

In the post-orbital part of the head there are distinguished, at least in most Teleosteous Fishes and many Ganoids, (Fig. [24]) the præoperculum, a sub-semicircular bone, generally with a free and often serrated or variously-armed margin; the operculum, forming the posterior margin of the gill-opening, and the sub-operculum and interoperculum along its inferior margin. All these bones, collectively called opercles, form the gill-cover, a thin bony lamella covering the cavity containing the gills. Sometimes they are covered with so thin a membrane that the single bones may be readily distinguished; sometimes they are hidden under a thick integument. In some cases the interoperculum is rudimentary or entirely absent (Siluroids).

Gill-opening.

The Gill-opening is a foramen, or a slit behind or below the head, by which the water which has been taken up through the mouth for the purpose of breathing is again expelled. This slit may extend from the upper end of the operculum all round the side of the head to the symphysis of the lower jaw; or it may be shortened and finally reduced to a small opening on any part of the margin of the gill-cover. Sometimes (Symbranchus) the two openings, thus reduced, coalesce, and form what externally appears as a single opening only. The margin of the gill-cover is provided with a cutaneous fringe, in order to more effectually close the gill-opening; and this fringe is supported by one or several or many bony rays, the branchiostegals. The space on the chest between the two rami of the lower jaw and between the gill-openings is called the isthmus.

Fig. 2.—Head of Mordacia mordax, showing the single nostril, and seven branchial openings.

The Sharks and Rays differ from the Teleosteous and Ganoid fishes in having five branchial slits (six or seven in Hexanchus and Heptanchus), which are lateral in the Sharks, and at the lower surface of the head in the Rays (Fig. [1], p. 34). In Myxine only the gill-opening is at a great distance from the head; it is either single in this family (Cyclostomi), or there are six and more on each side (Fig. [2]).

Tail.

In the Trunk are distinguished the back, the sides, and the abdomen. It gradually passes in all fishes into the Tail; the termination of the abdominal cavity and the commencement of the tail being generally indicated by the position of the vent. The exceptions are numerous: not only certain abdominal organs, like the sexual, may extend to between the muscles of the tail, but the intestinal tract itself may pass far backwards, or, singularly, it may be reflected forwards, so that the position of the vent may be either close to the extremity of the tail or to the foremost part of the trunk.

In many fishes the greater part of the tail is surrounded by the fins, leaving only a small portion (between dorsal, caudal, and anal fins) finless; this part is called the free portion or the peduncle of the tail.

Fins.

The Fins are divided into vertical or unpaired, and into horizontal or paired fins. Any of them may be present or absent; and their position, number, and form are most important guides in determining the affinities of fishes.

The vertical fins are situated in the median dorsal line, from the head to the extremity of the tail, and in the ventral line of the tail. In fishes in which they are least developed or most embryonic, the vertical fin appears as a simple fold of the skin surrounding the extremity of the tail In its further progress of development in the series of fishes, it gradually extends more forwards, and may reach even the head and vent. Even in this embryonic condition the fin is generally supported by fine rays, which are the continuations of, or articulated to, other stronger rays supported by the processes or apophyses of the vertebral column. This form of the vertical fin is very common, for instance in the Eels, many Gadoid, Blennioid and Ganoid fishes in which, besides, the rays have ceased to be simple rods, showing more or less numerous joints (simple articulated rays; Fig. [3]). Branched rays are dichotomically split, the joints increasing in number towards the extremity.

The continuity of the vertical fin, however, is interrupted in the majority of fishes; and three fins then are distinguished: one in the dorsal line—the dorsal fin; one in the ventral line behind the anus—the anal fin; and one confined to the extremity of the tail—the caudal fin.

Fig. 3.