SIBLEY: ORNITHOLOGY 



635 



subspecific ''splitting" has caused some systematists to propose that trinomials 

 should be discarded or at least withdrawn from the protection of the Interna- 

 tional Eules of Zoological Nomenclature. Thus, in 1953, w^e see the beginning 

 of a third phase in the description of geographic variation. Just as the recogni- 

 tion of geographic subspecies originally resulted from the combination of the 

 development of evolutionary theory and the growth of collections so the present 

 dissatisfaction results from the same factors. The theoretical basis has now, for 

 continental situations at least, outstripped the descriptive method and collec- 

 tions are now large enough frequently to reveal the true details of clinal varia- 

 tion. It is yet too early to discern the outcome but the most hopeful approach 

 will probably be found in a numerical evaluation of clines for only in numbers 

 do we have a means for expressing or describing continuous variation. Although 

 Sharpe's prediction thus proves to have contained a measure of truth, his advo- 

 cacy of adherence to strict binomialism is certainly not the answer to the problem. 



The Anatomy and Classification of Birds 



The earliest systems of classification were based either upon external charac- 

 ters such as the bill and foot structure or upon characteristics of habit (swim- 

 ming, running, etc.). The famous English anatomist, Richard Owen (b. 1804, 

 d. 1892), devoted a number of papers to avian anatomy, and the second volume 

 of his three-volume work on vertebrate anatomy (1866-1868) was concerned 

 to a large extent with birds. Johannes Miiller (b. 1801, d. 1858) proposed 

 (1847) a division of the passerines upon the basis of the structure of the syrinx, 

 a method still followed. 



In 1867 Thomas Henry Huxley (b. 1825, d. 1895) developed a classification 

 of birds upon the structure and relative positions of the palatal bones. The fal- 

 lacy of attempting to base broad conclusions upon such a narrow basis was not 

 immediately apparent and the palatal structure has been used by many subse- 

 quent workers as a basis for ordinal groupings. Recently (e.g., McDowell, 1948, 

 and Hofer, 1949) there have been strong doubts cast upon the validity of Hux- 

 ley's palatal types. 



Alfred Henry Garrod (b. 1846, d. 1879) fell into similar difficulties when 

 he based his classification primarily upon the arrangement of the carotid arteries 

 (1873a) and certain pelvic muscles (1873b, 1874). His "pelvic muscle formula" 

 has been used extensively and George E. Hudson has recently (1937) re-evalu- 

 ated and extended Garrod 's formula. 



William A. Forbes (b. 1855, d. 1883) and Hans F. Gadow (b. 1855, d. 1927) 

 produced a long series of reports on bird anatomy. Gadow (1891) wrote the 

 section on avian anatomy for Bronn's Klassen unci Ordnungen des Thier-Reichs. 

 In this monumental work Gadow brought previous studies up to date and at- 

 tempted to describe the complete morphology of the bird, including function 

 and homologies. At about the same time (1888) there appeared the great two- 

 volume work of Max Fiirbringer (b. 1846, d. 1920), in which he assembled an 

 enormous amount of anatomical information and carefully weighed the charac- 

 ters of value in classification. He recognized that the flightless groups were not 

 necessarily monophyletic. Flirbringer's work is still the classic of bird anatomy. 



To some opponents of Darwinism analogy and homology were of equal taxo- 



