330 Dr. C. Lutkcn on the Limitfi and 



cipal modern centres of palajiclithyological investigations ; but 

 (speaking, however, of a time wliicli already belongs to tlie 

 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 classitication of the 

 fishes of the Devonian system, a work truly marking an 

 epoch in pateichthyology, has remained almost unknown on 

 the Continent. 



Tiie first ])ortion of my work is exclusively of an historical and 

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

 although it serves as the basis of the following })art. Passing 

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

 Johannes Miiller, Stannius, Gegenbaur, Williamson, Kiilliker, 

 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 z()Ogra])hic charac- 

 ters, nor those borrowed from anatomy and histology (/. e. the 

 microscopic examination of the scales) having ])een capable of 

 remedying this defect. The restricted space wliicli you will 

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

 pressing my 0])inion upon all the points of the external and 

 internal structure of these animals, to which more or less 

 importance has l)cen 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 will 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 ]jroposes sulisidiarily 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 ftir from being able to ap- 

 prove of his principal proposition of striking this tribe com- 

 pletely out of the zoological system — a proposition Avhicli is 

 not supjiorted 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 which, as we shall soon show, would 

 be quite contrary to nature. 



The theoretical or constructive method, that of zoographie 

 or zootomical characters, having therefore failed, it will be 

 necessary to apply to this question the synthetical or com])ara- 

 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 ichthyology, from 1H41 to 18H0. 



