330 Dr. C. Liitken on the Limits and 



cipal modern centres of palreiclithyological investigations ; but 

 (speaking, however, of a time which ah-eady belongs to the 

 past), unfortunately, the English authors have generally had 

 but little knowledge of the works of their colleagues on the 

 shores of the Danube, and vice versa. Thus the important and 

 excellent memoir of Prof. Huxley on the classification of the 

 fishes of the Devonian system, a work truly marking an 

 epoch in pateiclithyology, has remained almost unknown on 

 the Continent. 



The first portion of my work is exclusively of an historical and 

 critical character, and will only be mentioned here very briefly, 

 although it serves as the basis of the following part. Passing 

 in review the more or less important writings* of Agassiz, 

 Johannes Miiller, 8tannius, Gegenbaur, Williamson, Kolliker, 

 Heckel, Wagner, Huxley, Kner, &c., I have shown that no 

 one has ever been able to give an exact definition of what is a 

 Ganoid, neither the external or so-called zoographic charac- 

 ters, nor those borrowed from anatomy and histology [i. e. the 

 microscopic examination of the scales) having been capable of 

 remedying this defect. The restricted space which you will 

 devote to this summary will, however, prevent me from ex- 

 pressing my opinion upon all the points of the external and 

 internal structure of these animals, to which more or less 

 importance has been ascribed, with more or less justice, in 

 connexion with their classification. I shall abide by the testi- 

 mony of the late Dr. Kner, who said with so much reason 

 that it Avill be impossible to give any definition of the order 

 Ganoidei if we desire to maintain the limits which are gene- 

 rally assigned to it ; and I also take my place on his side 

 when he proposes subsidiarily to restrict its limits and to re- 

 duce it from the rank of a subclass or order to a lower place 

 in the systematic scale. But I am far from being able to ap- 

 prove of his principal proposition of striking this tribe com- 

 pletely out of the zoological system — a proposition which is 

 not supported by any indication as to the eventual distribution 

 of this great group of diverse types among the other suborders 

 of the class of fishes, and whicli, as we shall soon show, would 

 be quite contraiy to nature. 



The theoretical or constructive method, that of zoographic 

 or zootomical characters, having therefore failed, it will be 

 necessary to apply to this question the synthetical or compara- 

 tive method, a work of labour and patience, it is true, but 

 always leading with certainty to the goal, — that is to say, the 

 method which consists in ranging the known types in accord- 



* At the end of my memoir there is a list of the principal publications 

 upon this division of iehthj'ology, from 1841 to 1869. 



