554 



THE AMEBIC AN NATURALIST [Vol. XLVIII 



one on each half of the part covered, with an ultimate 

 center at the base of the neck, usually the last spot to re- 

 main when the area is much reduced. 



In albinistic individuals, that is, those in which restric- 

 tion of the pigment areas has taken place, the neck 

 patches are usually first reduced at the upper part of the 

 throat, so that a white patch appears from the chin to 

 upper throat, as commonly seen in street pigeons; in 

 others, however, the restriction may be at the posterior 

 end of the patch, so that a white ring develops at the 

 base of the neck. 



In many birds the neck patches have been much devel- 

 oped as characteristic pigmented areas. Two general 

 categories may be here distinguished : ( 1 ) those in which 

 the neck is rather uniformly colored all about, and (2) 

 those in which the ventral portion is heavily pigmenti 

 and the dorsal portion much less so. In the latter belo: 

 such birds as the black-capped chickadee (Penthestes 

 atricapillus) with a black throat hut a pale neck, 

 too, the golden-winged warbler [Vermivora chrysop- 

 trra). In this latter category it is probable that a 

 ond factor is present, comparable to that producing a 

 centrifugal type of pigmentation in mammals, such for 

 example as in the Himalayan breed of rabbit, which lias 

 the end of the nose and the feet black-pigmented, contrary 

 to the usual rule of normal areal reduction where the 

 extremities are the first to become white. That this is 

 a separate category from a physiological standpoint is 

 indicated by its behavior in heredity as worked out so 

 admirably by Faxon (1913) in the case of the Brewster's 

 warbler. He discovered that the black throat as present 

 in the golden-winged warbler is recessive in the cross 

 with a related species, the blue-winged warbler (Ver- 

 mivora pinus), a yellow-throated bird. The offspring 

 of this cross have white throats, — the so-called V. leuco- 

 bronchialis. The black throat patch may be evidence of 

 "centrifugal" pigmentation as defined farther on (p. 53). 

 The essential bilaterality of such a throat patch is 



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