SBC. II PRINCIPLES AND PRACTICE OF CLASSIFICATION loi 



mucli of a fixture in Nature's museum as any specimen in the 

 naturalist's cabinet. Crops of classifications have been sown in the 

 fruitful soil of such blind error, but no lasting harvest has been 

 reaped. The confusion thus engendered has brought about the 

 inevitable reaction ; and the fashion of the present day is decidedly 

 the opposite extreme, — that of counting external features of little 

 consequence in comparison with anatomical characters. Too much 

 time has been wasted in arguing the superiority of each of- these 

 characters for the purposes of classification ; as if a natural classi- 

 fication should not be based upon all points of structure ! as if 

 internal and external characters were not reciprocal and mutually 

 exponent of each other ! But the genius of modern taxonomy 

 seems to be so certainly right, — to be tending so surely, even if 

 slowly, in the direction of the desired consummation, that all 

 differences of opinion, we may hope, soon will be settled, and 

 defect of knowledge, not perversity of the mind, be the only 

 obstacle left in the way of success. The taxonomic goal is not now 

 to find the way in which birds may be most conveniently arranged, 

 described, and catalogued ; but to discover their pedigree, and so 

 construct their family-tree. Such a genealogical table, or 'phylum 

 (Gr. t^vXov, phulon, tribe, race, stock), as it is called, is rightly con- 

 sidered the only taxonomy worthy the name, — the only true or 

 natural classification. In attempting this end, we proceed upon 

 the belief that, as explained above, all birds, like all other animals 

 and plants, are related to each other genetically, as offspring are to 

 parents ; and that to discover their genetic relationships is to bring 

 out their true affinities, — in other words, to reconstruct the actual 

 taxonomy of Nature. In this view, there can be but one natural 

 classification, to the perfecting of which all increase in our knowledge 

 of the structure of birds infallibly tends. The classification now in 

 use, or coming into use, is the result of our best endeavours to 

 accomplish this purpose, and represents what approach we have 

 made to this end. It is one of the great corollaries of that theorem 

 of Evolution which most naturalists are satisfied has been demon- 

 strated. It is necessarily a 



Mopphologieal Classifleation ; that is, one based solely upon 

 consideration of structure or form (/xop<^)7, morphe, form) ; and for 

 the following reasons : Every offspring tends to take on precisely 

 the structure or form of its parents, as its natural physical heritage ; 

 and the principle involved, or the law of heredity, would, if nothing 

 interfered, keep the descendants perfectly true to the physical 

 characters of their progenitors ; they would " breed true " and be 

 exactly alike. But counter-influences are incessantly operative, in 

 consequence of constantly varying external conditions of environ- 

 ment ; the plasticity of organisation of all creatures rendering them 



