1 6 THE CLASSIFICATION OF BIRDS 



easily be made ; but in this expectation he is doomed to absolute 

 disappointment. It is very easy to group genera into families, it 

 is not very difficult to arrange families into suborders, but to take 

 a retrospect of the history of Birds so far back as to discover the 

 genealogy of the suborders, and arrange them into orders and sub- 

 classes, is an unsolved problem. Most writers on classification 

 have attempted to determine the limits of the higher groups, a 

 few have attempted roughly to define the orders, but, so far as I 

 know, no one has been rash enough to diagnose the subclasses of 

 birds except myself. My first attempts were very imperfect, and 

 no one is more conscious of the imperfections of my last attempt 

 than I am ; but it seems to me that every attempt that shows the 

 independent development of characters to be fewer in number or 

 smaller in importance than previous classifications demand is a 

 step in the right direction. 



Perfection appears to be unattainable, possibly because we are 

 not yet working on the right lines. Shuffle the cards as we may, 

 we soon find that no possible combination of families can be made 

 without placing some of them in such a position , that makes it 

 imperative to assume the independent development of apparently 

 very important characters in very distantly related orders. Indeed 

 so constantly do we find characters which seem to be most difficult 

 of acquirement, but which must have been independently acquired 

 under every possible arrangement, that we are forced to the con- 

 clusion that it is not, as might naturally be supposed, a rare 

 exception to find a character which has been independently 

 acquired by two or more groups ; but that, on the contrary, it is 

 very exceptional to find any character other than those which are 

 common to all Birds which has not been acquired by two or more 

 groups independently of each other. 



It must be constantly borne in mind that no character which 

 has not been derived from inheritance has the smallest taxonomic 

 value. Those characters which have been independently acquired 

 are perfectly useless for purposes of classification ; they throw no 

 light whatever, not even the smallest ray, upon the genetic affinity 

 of the groups which possess them : no one of them, nor any number 

 of them, must be allowed for one moment to influence the 

 judgment; they must be totally ignored. The pre-Darwinian 

 naturalists recognised this fact, and admitted that some similari- 

 ties of character were marks of affinity, whilst others were only 

 marks of analogy. 



