EVOLUTION OF THE COLORS OF BIRDS. 323 



merely two dichroic species, in one of which (H. pinus) 

 the Xanthochroic (yellow) phase, and in the other 

 (H. chrysoptera) the leucochroic (white) phase represents 

 the normal plumage and admitting that these two 

 species, in their various conditions, hybridize (which 

 seems to be an incontrovertible fact) we have an easy 

 and altogether plausible explanation of the origin of the 

 almost interminably variable series of specimens which 

 have found their way into the ' waste-basket ' labelled 

 ' H. leucobronchialis.' ' 



Whatever view may prove to be the correct one, the 

 important point to note in this connection is that olive 

 green and yellow seem to be very closely related to gray 

 and white, and that the latter has the appearance of 

 being a bleached out phase of the former, due perhaps 

 to the failure to deposit the pigment in sufficient quanti- 

 ties. The accompanying table shows the probable gene- 

 alogy of the genus. I am largely indebted to Coues' 

 Key for the specific characters, which are there stated in 

 a particularly terse and comprehensive table. 



