492 PROCEEDINGS OF THE ACADEMY OF [1898. 



Thus from the time of Nitzsch down to the present day, the 

 classification of birds has gone through many changes and many 

 phases at the hands of the ornithologists of the succeeding genera- 

 tions as they have passed. The greatest advances have been made 

 since the scientific demonstration of the law of organic evolution 

 and the derivation of birds became known, and these by the men 

 who have studied the subject from that standpoint. Were it pos- 

 sible for us now to know the complete biology of every bird-form 

 that has existed upon the earth since birds as birds came into exist- 

 ence, there would be among ornithologists an agreement of opinion 

 upon their classification, the world over, within a twelvemonth. If 

 half the species that have existed were known, the scheme would 

 almost work itself out. As it is, we probably see to-day in the 

 world's avifauna but a paltry remnant of that enormous and un- 

 known host, and it will be generations yet to come ere there will be 

 a consensus of opinion upon the affinities of this puzzling and very 

 homogeneous group of vertebrates. When compared with other 

 major groups of animals, either vertebrate or invertebrate, the 

 structural differences to be found among the forms making up the 

 natural minor groups of existing birds are far less apparent than in 

 any one of them. Taken in their entireties, the difference between 

 an Apteryx and a Humming-bird morphologically, is not to be com- 

 pared with what exists when thus contrasted, between such forms, 

 for example, as a man and an Ornithorhynchus among mammals, or 

 between a Lancelet and a Bass among fishes. Birds are an extremely 

 compact group, and the disposition is altogether too prevalent in 

 attempts to classify them, to accord too high rank to not a few of the 

 divisions above the family. Were birds fishes, the entire congrega- 

 tion of them, would hardly make more than a respectable order. 

 They are a lucky lot of closely affined volant feathered reptiles that 

 have specifically multiplied at a wonderful rate since they sprang 

 into existence, and as useful and as charming as the majority of them 

 are in nature, their taxonomy nevertheless has puzzled the wits of 

 many a man since Aristotle lived, and will doubtless continue to do 

 so in the years to come. To arrive at their true affinities and a 

 natural grouping of the class, it will be necessary to utilize every 

 fact that we possess in regard to their biology ; by this it is meant 

 every palreontological fact; every fact referring to geographical dis- 

 tribution for all time ; every morphological fact ; besides all that is 

 known of their biology, habits, and development. In so far as their 



