Lacepède had to contend with great difficulties in the preparations of his Histoire des poissons (Paris, 1798-1803, 5 vols.), which was written during the most disturbed period of the French Revolution. A great part of it was Lacepède. 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 inaccessible to him for a long time. His work, therefore, abounds in the kind of errors into which a compiler is liable to fall. Thus the influence of Lacepède on the progress of ichthyology was vastly less than that of his fellow-labourer; and the labour laid on his successors in correcting numerous errors probably outweighed the assistance which they derived from his work.

The work of the principal students of ichthyology in the period between Ray and Lacepède was chiefly systematizing and describing; but the internal organization of fishes also received attention from more than one great anatomist. Albrecht von Haller, Peter Camper and John Hunter examined the nervous system and the organs of sense; and Alexander Monro, secundus, published a classical work, The Structure and Physiology of Fishes Explained and Compared with those of Man and other Animals (Edin., 1785). The electric organs of fishes (Torpedo and Gymnotus) were examined by Réaumur, J. N. S. Allamand, E. Bancroft, John 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 Salmonidae was known and practised by J. G. Gleditsch (1764).

Bloch and Lacepède’s works were almost immediately succeeded by the labours of Cuvier, but his early publications were tentative, preliminary and fragmentary, so that some little time elapsed before the spirit infused into ichthyology by this great anatomist could exercise its influence on all the workers in this field.

The Descriptions and Figures of Two Hundred Fishes collected at Vizagapatam on the Coast of Coromandel (Lond., 1803, 2 vols.) by Patrick Russel, and An Account of the Fishes found in the River Ganges and its Branches (Edin., 1822, 2 vols.) by F. Hamilton (formerly Buchanan), were works distinguished by greater accuracy of the drawings (especially the latter) than was ever attained before. A Natural History of British Fishes was published by E. Donovan (Lond., 1802-1808); and the Mediterranean fauna formed the study of the lifetime of A. Risso, Ichthyologie de Nice (Paris, 1810); and Histoire naturelle de l’Europe méridionale (Paris, 1827). A slight beginning in the description of the fishes of the United States was made by Samuel Latham Mitchell (1764-1831), who published, besides various papers, a Memoir on the Ichthyology of New York, in 1815.

G. Cuvier (1769-1832) devoted himself to the study of fishes with particular predilection. The investigation of their anatomy, and especially their skeleton, was continued until he had succeeded in completing so perfect a framework Cuvier. of the system of the whole class that his immediate successors required only to fill up those details for which their master had had no leisure. He ascertained the natural affinities of the infinite variety of forms, 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 formed connections with almost every accessible part of the globe; and for many years the museum of the Jardin des Plantes was the centre where all ichthyological treasures were deposited. Thus Cuvier brought together a collection which, as it contains all the materials on which his labours were based, must still be considered as the most important. Soon after the year 1820, Cuvier, assisted Valenciennes. by one of his pupils, A. Valenciennes, commenced his great work on fishes, Historie naturelle des Poissons, of which the first volume appeared in 1828. After Cuvier’s death in 1832 the work was left entirely in the hands of Valenciennes, whose energy and interest gradually slackened, rising to their former pitch 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.

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. Sparoïdes. Branchies labyrinthiques.
Polynèmes. Chétodonoïdes. Lophioïdes.
Mulles. Scombéroïdes. Gobioïdes.
Joues cuirassées. Muges. Labroïdes.
Sciénoïdes.
b. Malacoptérygiens.
Abdominaux. Subbrachiens. Apodes.
  ——   ——   ——
Cyprinoïdes Gadoïdes. Murénoïdes.
Siluroïdes. Pleuronectes.
Salmonoïdes. Discoboles.
Clupéoïdes.
Lucioïdes.

2. A Mâchoire Supérieure Fixée.