128 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



wide range and tliorougbiiess of their researches, have likewise adopted most of the families 

 proposed by the author when they chanced to treat of forms embraced in any of them. Such are 

 President David S. Jordan and Prof. Charles H. Gilbert, of the University of California, Dr. G. 

 Brown Goode, Director of the United States National Museum, and Dr. Tarletou P>eau, the Curator 

 of Fishes of the same museum. Prof. E. D. Cope, while often differing, has also accommodated his 

 views in many instances to those enunciated by myself. When so many independent and eminent 

 authorities more or less agree, there is good reason to believe that the views in which they concur 

 can not be very far M'ide of the 'truth, however much they may deviate from those prevalent in 

 other parts of the world. 



For while there is essential accord among American ichthyologists as to the limits of families, 

 the divergence among them being slight, there is a great divergence in that respect from most 

 European icthyologists. It may be well, then, to sustain the current American usage in the limi 

 tatiou of the families of fishes by reference to the treatment of well-studied groups of other classes 

 by the most competent European authorities. 



The illustrious Huxley, in his memoirs and well-known volume on the crayfishes and their rela- 

 tions, has exemplified the extent to which family ditterentiation should be carried, in his work. 

 An equally celebrated and profound German naturalist. Prof. Hiickel, in the various classes which 

 he has studied, has adopted similar principles. The numerous ornithological authors, forming so 

 large a contingent of the army of science, have even carried the discrimination of families to a 

 much greater extent. 



It is scarcely possible that anyone who should carefully study the morphology and character- 

 istics generally of the families of passerine birds, for example, and who should likewise survey 

 the morphology and characteristics of the families of fishes, could deny that there is scarcely one 

 (if any) of the families of fishes based upon characters so trivial as those which have served for the 

 differentiation of the great majority of those belonging to the great group of Passeres. If, there- 

 fore, the general zoologist has the slightest desire to be consistent, he must either reject most ot 

 the families of birds and recombine them or apply a far stricter analysis to the families of fishes 

 than is generally used in Europe. But, indeed, we have not to go outside the classes of fishes to 

 notice inconsistencies. Anyone who i-eviews the characteristics on which the families of Percoid- 

 ean and Scombroidean fishes have been distinguished must recognize that the distinctions which 

 have been employed to separate them are of far less value and significance than t"he characters 

 which differentiate various constituents or constituents in the sets of families as recognized by 

 ichthyologists of the old school. 



The author insists, as in previous publications, on the entirely provisional nature of the pres- 

 ent arrangement. Changes — grave changes — must neces.sarily be made in the system when the 

 species shall be studied in a more scientific way than has been generally done heretofore. Many 

 families are entirely unknown in an anatomical point of view, and until their structure has been 

 investigated and carefully compared with that of others, their systematic relations must remain 

 doubtful. No scientific investigator should fear to change his opinion. An obstinate persistence 

 in ancient views because they have been once adopted has been too long detrimental to the inter- 

 ests of systematic ichthyology, and such obstinacy has retarded the general progress of science for 

 twenty to thirty years. While the aspect of every other branch of vertebrate zoology has entirely 

 changed within that period, ichthyology, the most complex and the least advanced of all, might 

 appear to the casual observer to have had a more certain basis than any, inasmuch as tlie text- 

 books of a past generation have essentially the same system as the latest. Either almost omnis- 

 cience and preseience were the attributes of the guides of the past who keep to the same path in 

 the present, or obstinacy and blindness to an extraordinary degree have been manifested. To a 

 great extent ichthyology has been limited to descriptions of species or habits, and taxonomic prin- 

 ciples have been quite neglected. One author even, treating of the fish fauna of Great Britain, had 

 appreciated a few of the faults of the system he adopted, and yet seriously gave as a reason for 

 adopting it that "specimens are arranged in the national collection in accordance with it."* If 

 such reasons were generally regarded as sufficient we might well despair of any rapid progress of 



* Day's Fishes of Great Britain and Ireland, vol. i, p. xxix, 1884. 



