1920.] Letters, Extracts, and Notes. 965 



At the outset conspicuous geograpliic variations were 

 mistaken for constant characters and described as species. 

 When larger series were available for study, the mistake 

 was partially discovered, and the apocryphal species were 

 demoted to the rank of varieties. Later, the term variety 

 was superseded by the term subspecies. It was assumed 

 that geographic \ariations are incipient species. There is no 

 valid reason for such an assumption. We are not endovved 

 with the gift of prophecy, and can not foretell the remote 

 future of any variation having evolutionary possibilities. 

 It matters not whether the variation be geographic, dichro- 

 matic, or individual. Moreover, it is not known liow 

 existing bird species were evolved. The manner of the 

 unfolding is lost iu the mists of the past. 



Dichromatic variations (possible saltations) have also fared 

 ill at the hands of systematists. Many such variations have 

 been described as species. Some of them were ultimately 

 identified as colour phases of species. Other?, because of 

 differences in the geographic distribution of phases and lack 

 of correlation with environmental conditions, were relegated 

 to the category of intergrading species. 



In nature, fundamental bird units abound. The indi- 

 viduals composing these units possess a peculiar assemblage 

 of characters, an assemblage that absolutely separates them 

 from all other bird individuals. These units are conven- 

 tionally styled species. Called by any other name, they 

 would be as real. Geographic and dichromatic variations 

 are inconstant variations within bird units. If trinomial or 

 binomial names are applied to these variations, a false 

 impression of unity is conveyed that is difficult to expel 

 from the mind when once entertained. In short, no magic 

 words or question-begging phrases can make geographic 

 and dichromatic variations units. 



It has often been urged that the subspecies theory is a 

 convenient scheme for handling geographic variations and 

 an important aid in tracing migration routes. One has only 

 to read a recent systematic monograph of a bird group, 

 treated on the subspecies basis, to learn that the author has 



