MUSEUM OF COMPARATIVE ZOOLOGY. 351 



question yet to be decided." Dr. Coues, however, in his " List of the 

 Birds of Fort Whipple, Arizona," * says he thinks there can be no doubt 

 respecting the propriety of separating the " western turkey from the com- 

 mon species of the Eastern United States"; but he has given us no infor- 

 mation as to how great the differences between them are, or in what they 

 consist. As mentioned by Gould and by Baird, the Mexican bird differs 

 from the eastern one only in being lighter colored, and in having, in 

 correlation with the generally lighter color of the plumage, the terminal 

 band of the tail, as also the tips of the tail coverts, whitish instead of pale 

 brown, as the eastern bird usually has them. This, however, seems by no 

 means necessarily a specific difference, it being only a slight geographical 

 variation, not restricted to the turkey, but which runs through most spe- 

 cies of both birds and mammals that have the same distribution ; the 

 probable cause of which variation I have already adverted to in Part III. 

 The common eastern turkey occasionally approaches much nearer to the 

 so-called Mexican bird than appears to be generally supposed. According 

 to some authors, the tip of the tail in M. gallopavo is never whitish, but 

 " plain chestnut, lighter than the ground color " of the tail. Yet of five 

 specimens in the Museum of Comparative Zoology from one of the West- 

 ern States, probably either Ohio or Michigan, two correspond with the 

 description of the assumed typical M. gallopavo, two very nearly as well 

 with that of the so-called M. mexlcana, and one is intermediate between 

 them. Three of them are decidedly lighter colored, and possess a lighter 

 terminal band to the tail than they should to correspond with the true M. 

 gallopavo as recently defined. I have, on the whole, no hesitancy in refer- 

 ring the .1/. mexicana Gould to the M. gallopavo Linne. The unquestionable 

 specific identity of the domestic turkey with the wild one of the Eastern 

 United States, though originally derived from the Mexican bird, seems 

 further to support this view. From the great constancy of the white on 

 the tail and its coverts in the domestic turkey, it has been thought to more 

 resemble the western bird, or the M. mexicana, than the eastern. I need, 

 however, only to recall the testimony of Dr. Bachman, already given in 

 discussing another point, to show that it has necessarily no such signifi- 

 cance. It will be remembered that Dr. Bachman states that he had 

 known the wild birds of the Atlantic States, when kept entirely by them- 

 selves, to become more or less white under confinement in three genera- 

 tions.f Instead of this being either a " reversion " or a distinctive specific 

 feature, it can be regarded only as the result of a diminution of the color- 

 ing matter through degeneracy, under the influences of domestication. 



* Proc. Phil. Acad. Nat. Sci., Vol. XVIII, p. 93, 1866. Republished under the title 

 of " Prodrome of a Work on the Ornithology of Arizona Territory." 



t Mr. Darwin mentions a similar fact as having happened iu England. (Animals and 

 Plants under Domestication, Vol. I, p. 354). 



