180 THE LESSON OF EVOLUTION 



in the Chatham Islands, and P. traversi in 

 Macquarie Island and a section in which the skin 

 between the eyes and the mouth is smooth. This 

 section contains P. chalconotus from New Zealand 

 and Stewart Island, P. campbelli from Campbell and 

 Auckland Island, P. colensoi from Auckland 

 Islands, and P. ranfurlyi from the Bounties. 



In P. carunculatus the naked skin of the lores is 

 at first smooth and then becomes carunculated , from 

 which we may infer that the carunculated section is 

 descended from the non-carunculated. Again, 

 several of the species have a white bar on the wing- 

 coverts and another across the lower back, which do 

 not appear until the birds are mature ; consequently 

 we may assume that the species with these white 

 bars are descended from those without them. All 

 the carunculated species have these white bars, 

 which is confirmatory evidence of their having des- 

 cended from the non-carunculated section. 



Of the non-carunculated species, P. stewarti is 

 the only one in which both white bars are present, 

 so that we can look upon it as the connecting link 

 between the two sections. P. ranfurlyi has an alar 

 bar, but shews only vestiges of the dorsal bar, so that 

 it must also be a descendant of the P. stewarti. 

 P. chalconotus is only a black variety of P. stewarti, 

 and sometimes has white feathers on its breast and 

 abdomen. In P. colensoi and P. campbelli there is 

 an alar bar but no dorsal one, and the alar bar is very 

 narrow in P. campbelli. In P. campbelli, also, the 

 throat only is white and the neck is dark ; while in 

 the adult P. colensoi both the throat and the fore 



