634 A CENTURY OF PROGRESS IN THE NATURAL SCIENCES 



cept and the Linnaean species and to overemiie tlic ohjectioiis of thoso who re- 

 fused to give up the binary system. 



Kleinschmidt admitted the existence of organic evolution but believed that 

 evolution had taken place within each Fonnenkreis following its special creation. 

 In 1926 he elaborated upon the Formenkreis concept but the weaknesses imposed 

 by his insistence on considering each "seed species" the result of special creation 

 were sharply criticized. Bernhard Eensch (b. 1900) was the chief critic of Klein- 

 schmidt 's concept. Rensch (1929) clarified the concept by proposing that Har- 

 tert's geographically varying species should be called "Rassenkreise" and two 

 or more closely related but monotypic species which are geographically comple- 

 mentary should be called "Artenkreise." These terms have not come into general 

 usage but they served to call further attention to the characteristics of geo- 

 graphically variable groups. 



The publication of Genetics and the Origin of Species (1937) by Theodosius 

 Dobzhansky marked the beginning of a new phase in avian systematics. This 

 book made a deep impression on naturalists by relating systematics to genetics. 

 Dobzhansky was largely responsible for bringing to the attention of taxonomists 

 the important developments in population genetics made by Sewall Wright in 

 the United States and R. A. Fisher in England. 



With the realization that studies of variation were capable of producing 

 important evidence of evolutionary processes a new method of investigation 

 developed. In 1941 Alden H. Miller (b. 1906) forcibly demonstrated the value 

 of examining large series of specimens in the study of variation. In his study 

 of the avian genus Junco Miller assembled 11,776 study skins. Special trips were 

 made to critical areas to collect adequate numbers of birds and the analysis of 

 variation utilized statistical techniques to indicate probable as well as observable 

 ranges of variation. Miller's Junco paper has served as the inspiration and the 

 pattern for a number of subsequent studies of speciation undertaken by his 

 students. 



Because of the relatively advanced state of avian systematics it was almost 

 inevitable that an ornithologist would produce the first synthesized treatment of 

 taxonomic practice and evolutionary theory. The synthesis was admirably pro- 

 vided in 1942 by Ernst Mayr (b. 1904). In his Systematics and the Origin of 

 Species Mayr gave systematics the first adequate integration of taxonomy, 

 genetics, and natural history. Mayr has continued to lead in the field of evolu- 

 tionary systematics. He was the prime mover in the founding of the Society 

 for the Study of Evolution in 1946, and the first editor (1947-1949) of the 

 journal Evolution. The contributors to this journal have incliided botanists, 

 geneticists, paleontologists, and zoologists, with a wide diversity of special in- 

 terests. The existence of the Society and the journal epitomizes the modern 

 synthesis of fields of thought which a few years ago were regarded as diverse 

 disciplines. Further evidence of this synthesis is provided by the recent (1953) 

 volume on methods and principles of systematic zoology coauthored by Mayr 

 and the entomologists, Linsley and Usinger. For a review of speciation in birds 

 and a bibliography of recent publications see Mayr, 1950. 



The prediction by Sharpe in 1909 that ternary nomenclature would eventually 

 overburden its users with names is currently finding new protagonists. The de- 

 scription of clinal variation is difficult to accomplish with names and excessive 



