Vol 'wi9 XVI ] Loomis, The Reality of Species. 237 



been misinterpreted and made the basis of apocryphal species and 

 their supposed hybridization on a grand scale. In the alleged 

 Junco species, for instance, possibly dichromatism or polychroma- 

 tism, originating in mutations, obtains along with geographic 

 variation. 



Vermivora leucobronchialis (Brewster) and Vermivora lawrencei 

 (Herrick) are not overlooked in this discussion. The evidence 

 thus far presented tends to prove that they are hybrids between 

 two species rather than intermediates of one dichromatic species. 1 

 Be this as it may, hybridization between unquestionable species 

 of birds is an abnormal and relatively rare occurrence. 



To affirm that bird species are concepts, is to ignore the facts 

 in the case. Ammodromus samuelis Baird and Melospiza fallax 

 Baird are concepts, but Melospiza melodia with all its geographic 

 variations is a reality. It is absolutely separated from Melospiza 

 lincolni and Melospiza georgiana and all other existing bird species. 

 Colaptes auratus is likewise a reality. In spite of its great dichro- 

 matic variation, it does not intergrade with any other woodpecker. 

 It is confidently stated that the great majority of the A. 0. U. 

 'Check-List' species are also realities, and the remainder time- 

 honored concepts based on inconstant variations, like Fulmarus 

 rodgersi Cassin, which is merely an extreme white phase of Ful- 

 wiarus glacialis (Linnseus). 2 



In a word, absence of intergradation among birds results in a 

 definite entity, the existing bird species. 



1 Cf. Faxon, Mem. Mus. Comp. Zool., Vol. XL, 1911. pp. 57-78. 

 » Cf. Proc. Calif. Acad. Sci., 4th Ser., Vol. II, Pt. II, 1918, p. 88. 



