124 Mr. G. M. Mathews on the [lb 



IS, 



green plumage has been lost, in both erythrism is missing, 

 in both xanthochroism is dominant, but in the one case 

 cyanism is a strong factor, in the other melanism is a new 

 and overpowering feature. I can see no reason for these 

 differences, as the environmental stresses seem similar. 



The immature of the north-eastern species {adscitus,Vl. III. 

 fig. 4), which is the cyanistic one, has the head yellowish 

 speckled with blackish, back with dull yellow scalloping, the 

 cheeks blue and white, the rump and under surface dull 

 greyish blue. The mature has the head and cheeks pale 

 yellow, the back scalloped with bright golden, the rump and 

 underparts greyish blue. Great variability in tone is seen in 

 the species, in some parts the blue having a greenish shade, 

 in others a greyish, while the cheeks are parti-coloured blue 

 and yellowish white. However, tlie xanthochroistic ten- 

 dency seems to be increasing, as the majority of fully adult 

 specimens have the yellow of the head encroaching on to the 

 throat and breast, and the more colour the paler it becomes, 

 suggesting an albinistic tendency. 



In the north-western species {venustus, PI. III. fig. 8), the 

 cyanism is entirely suppressed, being only seen in the cheeks, 

 which are parti-coloured blue and white. The head is wholly 

 black, the yellow-scalloped back being followed by a yellow 

 rump, the feathers, however, are tipped with black ; while the 

 under surface is also yellow, the feathers tipped with black, 

 and the bases black. An atavistic erythristic tendency 

 seems to have been recorded in a red forehead and even 

 a totally red head. The general progress appears to be 

 strongly melanistic, the black becoming more extensive, and 

 the yellow diminishing. 



It may help in appreciating these changes to indicate in 

 tabular form the dominating elements : — 



P. caledonicus Nearest ancesti'al, slight xanthochroism. 



P.jlaveolus Strong xanthochroism. 



■p. elegans Strong erythrism. 



P. icterotis Weaker erythrism, weak cyanism. 



P. exhnius Strong xanthochroism, strong erythrism. 



P. adsciUis Xanthochroism, strong cyanism. 



P. vemisins Xanthochroism, strong melanism. 



