For nearly a century the works of Belon and Rondelet continued to be the standard works on ichthyology; but the science did not remain stationary during that period. The attention of naturalists was now directed to the fauna of foreign countries, especially of the Spanish and Dutch possessions in the New World; and in Europe the establishment of anatomical schools and academies led to careful investigation of the internal anatomy of the most remarkable European forms. Limited as these efforts were as to their scope, they were sufficiently numerous to enlarge the views of naturalists, and to destroy that fatal dependence on preceding authorities which had kept in bonds even Rondelet and Belon. The most noteworthy of those engaged in these inquiries in tropical countries were W. Piso and G. Marcgrave, who accompanied as physicians the Dutch governor, Count Maurice of Nassau, to Brazil (1630-1644).
Of the men who left records of their anatomical researches, we may mention Borelli (1608-1679), who wrote a work De motu animalium (Rome, 1680, 4to), in which he explained the mechanism of swimming and the function of the air-bladder; M. Malpighi (1628-1694), who examined the optic nerve of the sword-fish; the celebrated J. Swammerdam (1637-1680), who described the intestines of numerous fishes; and J. Duverney (1648-1730), who investigated in detail the organs of respiration.
A new era in the history of ichthyology commences with Ray, Willughby and Artedi, who were the first to recognize the true principles by which the natural affinities of animals should be determined. Their labours stand in so intimate a connexion with each other that they represent but one great step in the progress of this science.
J. Ray (1628-1705) was the friend and guide of F. Willughby (1635-1672). They found that a thorough reform in the method of treating the vegetable and animal kingdoms had become necessary; that the only way of bringing Ray and Willughby. order into the existing chaos was by arranging the various forms according to their structure. They therefore substituted facts for speculation, and one of the first results of this change, perhaps the most important, was that, having recognized “species” as such, they defined the term and fixed it as the starting-point of all sound zoological knowledge.
Although they had divided their work so that Ray attended to the plants principally, and Willughby to the animals, the Historia piscium (Oxf., 1686), which bears Willughby’s name on the title-page and was edited by Ray, is their joint production. A great part of the observations contained in it were collected during the journeys they made together in Great Britain and in the various countries of Europe.
By the definition of fishes as animals with blood, breathing by gills, provided with a single ventricle of the heart, and either covered with scales or naked, the Cetaceans are excluded. The fishes proper are arranged primarily according to the cartilaginous or the osseous nature of the skeleton, and then subdivided according to the general form of the body, the presence or the absence of ventral fins, the soft or the spinous structure of the dorsal rays, the number of dorsal fins, &c. No fewer than four hundred and twenty species are thus arranged and described, of which about one hundred and eighty were known to the authors from personal examination—a comparatively small proportion, but descriptions and figures still formed in great measure the substitute for our modern collections and museums. With the increasing accumulation of forms, the want of a fixed nomenclature had become more and more felt.
Peter Artedi (1705-1734) would have been a great ichthyologist if Ray or Willughby had not preceded him. But he was fully Artedi. conscious of the fact that both had prepared the way for him, and therefore he did not fail to reap every possible advantage from their labours. His work, edited by Linnaeus, is divided as follows:—
(1) In the Bibliotheca ichthyologica Artedi gives a very complete list of all preceding authors who had 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 for all the various modifications of the organs, distinguishing 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 has fixed 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 manner which is adopted in the systematic works of the present day.
Artedi has been justly called the father of ichthyology. So admirable was his treatment of the subject, that even Linnaeus Linnaeus. could only modify and add to it. Indeed, so far as ichthyology is concerned, Linnaeus has scarcely done anything beyond applying binominal terms to the species properly described and classified by Artedi. His classification of the genera appears in the 12th edition of the Systema thus:—
A. Amphibia nantia.—Spiraculis compositis.—Petromyzon, Raía, Squalus, Chimaera. Spiraculis solitariis.—Lophius, Acipenser, Cyclopterus, Balistes, Ostracion, Tetrodon, Diodon, Centriscus, Syngnathus, Pegasus.