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 ab- 

 stracting 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. Puerbiinger'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 introduc- 

 tion 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 my friend ; moreover, I was naturally anxious to see what my 

 own resources would enable me to find out. This is my 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 why and 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 weigh the same characters 

 every time anew and in different ways, whenever we inquire into the 



