310 CALIFORNIA ACADEMY OF SCIENCES. 



following attempt to explain it according to the law of 

 pigment assortment may seem forced, but is suggested 

 for what it is worth. There can be no doubt that the 

 orchard oriole (Icterus spurius) was originated from 

 the same stock as the other orioles, from the fact that 

 the young plumage is almost identical in color with cor- 

 responding stages of other species. Here it seems that 

 an intensification of yellow has produced a reddish 

 brown instead of scarlet or crimson. In the same way, 

 it is not impossible that the rufous color of Pipilo has 

 been produced by the intensification of yellow, which 

 color is present in certain members of the genus, in- 

 cluding P. chlorurus. The combination of the yellow 

 with the black would produce the olive green of P. chlo- 

 rurus. As showing the relationship of P. fuscus, it is 

 to be noted that in this species the feathers of the belly 

 are white, basally, indicating that this part was formerly 

 as in P. maculatus. 



These birds are all the descendants of a streaked an- 

 cestor, but what factors have produced the wide diversity 

 at present exhibited we cannot well determine. Complete 

 and long continued isolation of the original species into 

 three sections may have started the different branches 

 upon widely different courses of evolution. Sexual 

 selection, recognition and protection have all played a 

 part in this. 



Genus Cardinalis 



, The Cardinals. 

 Genus Pyrrhuloxia 



(7) Adult male more conspicuously colored than 

 female; young similar to adult female, but duller. 



Prevailing colors, vermilion, carmine, black, brown, 

 buff, gray. 



Sexual selection alone can account for the colors of 

 this genus, the females having inherited a small portion 

 of the bright colors of the male. The fact mentioned 



