Page:Encyclopædia Britannica, Ninth Edition, v. 1.djvu/297

Rh AGASSIZ 275 &quot;by these universities for extending his knowledge of natural history, especially of botany. Having completed his academi cal course, he took his degree of doctor of medicine at Munich. Up to this time he had no particular inclination for the study of ichthyology, which soon afterwards became the great occupation of his life. Agassiz always declared that he was led into ichthyological pursuits through the follow ing circumstances: In 1819-20, Spix and Martius were engaged in their celebrated Brazilian tour, and on their return to Europe, amongst other collections of natural objects, they brought home an important one of the fresh water fishes of Brazil, and especially of the Amazon river. Unfortunately Spix did not live long enough to work out the history of these fishes ; hence it became necessary that some other naturalist should undertake the task of describ ing them. It is no insignificant proof of the reputation which Agassiz had already won, that, though little more than a youth just liberated from his academic studies, he was selected for this purpose. His attention being thus directed to the special subject of ichthyology, he at once threw himself into the work with that earnestness of spirit which characterised him to the end of his busy life. Thus, in 1828 we find him, after describing a new species of Cyuocephalus, publishing a description of a new cyprinoid fish. This was followed by a yet more elaborate research into the history of the cyprinoid and other fishes found in the lake of Neuchatel. Kapidly enlarging his plans, the publication of the last-named work was succeeded by the issue, in 1830, of a prospectus of a History of the Fresh- luater fishes of Central Europe. It was only in 1839, however, that the first part of this important publication appeared. The task of describing and figuring the Brazilian fishes of Spix and Martius was completed and the work published in 1829. Acquiring fresh confidence through these labours, he now contemplated a yet greater task. Having become a pro fessed ichthyologist, it was impossible that the fossil fishes with which the stratified rocks of his native mountains abound should fail to attract his attention. The rich stores furnished by the slates of Glarus and the limestones of Monte Bolca were already well known ; but very little had been accomplished in the way of the scientific study of them. Agassiz at once threw himself into this new field of labour with his wonted enthusiasm, and began the publication of the work which, more than any other, made him known to foreign naturalists, and laid the foundation of his world wide fame. Five volumes of his KecJierches sur les Poissons Fossiles appeared at intervals between the years 1833 and 1844. They were magnificently illustrated, chiefly through the labours of Dinkel, an artist of remarkable power in delineating natural objects. Agassiz soon found that his pakeontological labours rendered a new basis of ichthyological classification ab solutely necessary. The fossils rarely exhibited any traces of the soft tissues of fishes. They chiefly consisted of the teeth, scales, and fins, even the bones being perfectly preserved in but comparatively few instances. Hence the classifications of Cuvier and other naturalists were of little use to him in determining the mutual relations of the fossil forms. He therefore adopted his well-known classification, which divided fishes into four groups viz., Ganoids, Placoids, Cycloids, and Ctenoids. The first of these groups was chiefly represented amongst living fishes &quot;by the Lepidosteus or bony pike of the great American rivers; by the Polypterus or Bischir of the Nile; and by the sturgeon. The last fish has a wide geographical range; but the other two, which best display the characters on which Agassiz based his Ganoid class, are limited to the fresh-water rivers of local geographical areas. But in the Palaeozoic and Mesozoic ages it was strikingly otherwise. The Ganoids were the most remarkable as well as the most widely diffused of primeval fishes; we find them equally in the fresh-water deposits of the weald, in the marine deposits of the oolites, the chalk, and the magnesian lime stone, and in the more mixed and dubious deposits of the coal measures. Agassis, therefore, was fully justified in attaching very great importance to this hitherto unrecog nised class. Indeed, later ichthyologists e.g., J. M tiller and Professor Owen have found it necessary to retain the class in their recent classifications, though in a modified form. The remaining portions of Agassiz system have not been adopted by them ; but though they do not accept the terms Placoids, Cycloids, and Ctenoids as representing classes, all zoologists employ them as new and convenient adjectives, of the utmost value to students of systematic ichthyology. One reason for the rejection of Agassiz system by modern ichthyologists is the obvious one that he draws the characteristics of his classes from a single organ the skin and that not the most important. At the same time, it must be admitted that the Placoids, like the Ganoids, also constituted a natural group closely corre sponding with the l^isces cartilayinei of Cuvier and others. The distinction between Cycloids and Ctenoids was a much more trivial one, and needlessly separated closely-allied forms. It is only those who are familiar with the magnitude and difficulties of the task thus undertaken that can appreciate the daring courage of the youth who grappled with it. Under twenty-five years of age, and, as already observed, with limited financial resources, he nevertheless seems to have known no fear. He soon announced to geologists several important generalisations, the correctness of which has been confirmed by all sub sequent research. In particular, he pointed out that no examples of Cycloids and Ctenoids, comprehending the bulk of the fishes now seen in our markets, were to be found in rocks of older date than the cretaceous age. As the work proceeded it became obvious that it would over-tax the resources of the intrepid young zoologist, un less some additional assistance could be afforded to him. The British Association for the Advancement of Science wisely came to his aid, and the late Earl of Ellesmere better known in his youth as Lord Francis Egerton gave him yet more efficient help. The original drawings made for the work, chiefly by Dinkel, amounted to 1290 in number. These were purchased by the earl; but, with princely liberality, he left all that were necessary for the further prosecution of his labours in the hands of Agassiz. It was whilst he was thus engaged that Agassiz paid his first visit to England, for the purpose of studying the rich stores of fossil fishes with which this country abounds. He was then in his youthful prime a model of manly vigour and scientific enthusiasm; but amongst his many qualities none were more remarkable than the quickness with which he detected the peculiarities of any new fossil, and the retentiveness of his memory, which enabled him to make ready use of his newly-acquired knowledge. The consciousness that he possessed these powers led him occa sionally though, it must be allowed, but rarely to trust unduly to them, and made him sometimes hasty and off hand in his conclusions. But fossil ichthyology, though a very large subject, was insufficient to occupy his energetic mind. In 1837 we find him issuing the &quot; Prodrome &quot; of a monograph on the recent and fossil Echinodermata, the first part of which appeared in 1838 ; and in 1839-40 he published, in addi tion, two quarto volumes on the fossil Echinoderms of Switzerland. This division of the invertebrate animals was evidently a favourite one with him, since we find it the subject of numerous memoirs which appeared from time to time during his later life.