308 CALIFORNIA ACADEMY OF SCIENCES. 



being a tendency towards the assumption of a uniform 

 coloration. Climatic influences and isolation appear to 

 have played an important part in the origination of 

 specific and varietal differences. 



GENUS MELOSPIZA. THE SONG SPARROWS, ETC. 



(1) Adult male like female; young similar to adult. 



Prevailing colors, brown, rufous, gray, ashy, white. 



This genus is comparatively little modified from the 

 streaked ancestral plumage. The general effect of sun- 

 light upon pigmentation is shown by the tendency of 

 the breast to be white and the back dark, although the 

 bird is streaked both above and below. The special in- 

 fluence of the environment upon the colors is shown in 

 Plate XIII where the color of the back of each race is 

 marked in the locality inhabited by the respective form. 



GENUS PASSERELLA. THE Fox SPARROW, ETC. 



(1) Adult male like female; young like adult. 



Prevailing colors, brown, rufous, gray, white. 



The transition from a streaked to a uniform mode of 

 coloration is shown by the backs of P. iliaca and P. 

 iliaca unalaschcensis , which are races of the same species 

 probably largely due to climatic influences. Upon the 

 breast the primitive streaked plumage is replaced by the 

 second type of marking, the spot. The markings of 

 this genus are surprisingly like those of the thrush 

 family, and may well have been produced by the same 

 or similar influences. 



GENUS EMBERNAGRA. TEXAS SPARROW, ETC. 



(1; Adult male like female; young like adult (?). 



Prevailing colors, olive-green, brown, gray, buffy, 

 white, yellow. 



This genus appears as if it had been more brilliantly 

 colored in past time, but had lost most of its character- 



