248 BULLETIN OF TOE 



some cases difficult to distinguish. They can he satisfactorily investigated 

 only from extensive suites of specimens taken from the same locality 

 in the breeding season, and sufficiently extensive suites of this character 

 arc, with rare exception-, still wanting. In specimens taken during 

 migration it is difficult to determine what share of the variation is due 

 to birthplace and what to individuality. Whilst, however, the varia- 

 tions noticed cannot be always traced with certainty to their origin, 

 their bearing upon the general subject of variation within specific limits 

 is in no way vitiated. In considering hypothetical species, it is fre- 

 quently clearly evident that they are based in part upon slight and 

 tolerably constant climatic differences, and in part and sometimes wholly 

 upon the individual peculiarities of the single specimen upon which the 

 original description of the species was based ; in part, too, upon seasonal 

 differences, and upon characters of immaturity. It seems to me that in 

 the numerous clo-ely allied species of the ^.Egiutltus group, to cite a case 

 in point, some are based in part upon one and in part upon other of 

 these differences of a single circumpolar species. As already shown, 

 the bill in different specimens oF ^E. Unarms varies greatly in size, yet 

 an examination of a considerable series of specimens of several of its 

 allies shows an amount of variation in the bill closely approximate to 

 that seen in the specimens of the various assumed species of uEgiothus. 

 Much of the variation in color seen in the flocks of JEgiothi that visit 

 the Northern States in winter is due to age, yet it has been taken as 

 characteristic of different species. These birds only visiting us in 

 winter, those inhabiting widely distant localities in the breeding season 

 are probably then more or less associated. The light-colored specimens 

 are doubtless in part old or fully mature birds, or inhabitants in summer 

 of more northern districts than the browner or more fulvous ones, a 

 large portion of which, however, an; unquestionably young birds. The 

 short-hilled ones have also relatively longer seta; at the base of the 

 bill, which, by concealing a large portion of it, give it the appearance 

 of being shorter than it really is. Analogy would lead us to infer that 

 those with the shorter and more heavily clothed bills have a more 

 northern habitat than the others. 



The persistency with which nominal species when characterized by 

 " authorities " are retained in our literature is not a little remarkable. 

 If specimens from the original localities cannot lie found to exactly tit 

 the descriptions, the diagnosis is slightly amended to suit examples that 



