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Show 1892.] DR. H. GADOW ON THE CLASSIFICATION OF BIRDS. 229 4. On the Classification of Birds. By HANS GADOW, M.A., Ph.D., F.Z.S., Strickland Curator and Lecturer on Advanced Morphology of Vertebrata in the University of Cambridge. [Received March 12, 1892.] By undertaking, in 1884, the continuation of the part ' Aves' of Bronn's ' Klassen und Ordnungen des Thier-Reichs,' I became pledged not only to a descriptive account of the anatomical structure of birds, but also to a systematic treatment of this Class with its Orders. The anatomical portion has been written with the view of abstracting therefrom a classification. In the meantime (after Huxley, Garrod, Forbes, Sclater, and Reichenow's systems) have appeared several other classifications: one each by Prof. Newton, Dr. Elliott Coues, Dr. Stejneger, Prof. Fuerbringer, Dr. R. B. Sharpe, and two or three by Mr. Seebohm. Some of these systems or classifications give no reasoning, and seem to be based upon either experience in ornithological matters or upon inclination-in other words, upon personal convictions. Fuerbringer's volumes of ponderous size have ushered in a new epoch of scientific ornithology. No praise can be high enough for this work, and no blame can be greater than that it is too long and far too cautiously expressed. For instance, the introduction of " intermediate "groups (be they suborders orgentes) cannot be accepted in a system which, if it is to be a working one, must appear in a fixed form. In several important points I do not agree with m y friend ; moreover, I was naturally anxious to see what my own resources would enable m e to find out. This is m y apology for the new classification which I propose in the following pages. The author of a new classification ought to state the reasons which have led him to the separation and grouping together of the birds known to him. This means not simply to enumerate the characters which he has employed, but also to say whyand howhe has used them. Of course there are characters and characters. Some are probably of little value, and others are equivalent to half a dozen of them. Some are sure to break down unexpectedly somewhere, others run through many families and even orders; but the former characters are not necessarily bad and the latter are not necessarily good. The objection has frequently been made that we have no criterion to determine the value of characters in any given group, and that therefore any classification based upon any number of characters however large (but always arbitrary, since composed of non-equivalent units) must necessarily be artificial and therefore be probably a failure. This is quite true if we take all these characters, treat them as all alike, and by a simple process of plus or minus, i. e. present or absent, large or small, 1, 2, 3, 4, & c , produce a "Key," but certainly not a natural classification. To avoid this evil, we have to sift or weiyh the same characters every time anew and in different ways, whenever we inquire into the |