122 Mr. G. M. Mathews on the [Ibis, 



taking place by the revival of the cyanistic element, and 

 this has caused the back-feathers by interaction with the 

 erythristic element to become grey, while the blue tail- 

 feathers come into their own as seen in the eastern forms. 

 Then still the erythristic element is working, and we find 

 the grey eliminated in favour of red. All these stages can 

 be seen at once in a series from the west, and, moreover, 

 it appears that the grey phase is becoming the juvenile 

 plumage and the red the adult, the immature green of the 

 coast being lost ; further, on the coast the green is more or 

 less perpetual, the back and tail-feathers remaining in that 

 colour. We can guess that the climatic conditions in these 

 cases favour the changes denoted, but in other parts of 

 Australia similar climatic conditions are associated with 

 entirely different coloration. 



To return to the Tasmanian form ; on the islands of Bass 

 Straits we find it varying, being constantly darker, but in 

 one case larger, in the other smaller, while in the one it has 

 red under tail-coverts, in tlie other green. No reason for 

 this variation can be suggested at the present time. On the 

 mainland, as regards the south three species occur : one is 

 the mainland representative of the Tasmanian species in 

 which the xanthochroistic element has maintained itself, 

 and the bird has become practically wholly yellow, the blue 

 cheeks, blue shoulder-patch, blue (upper) tail-feathers, and 

 red forehead being unchanged. It has varied only in the 

 depth of the yellow. 



The second is the erythristic form of the group, and this 

 is the dominant species, so far as can be ascertained, in 

 eastern Australia. Commencing life with a red cap, red 

 breast and vent, blue cheeks and shoulder-patch, otherwise 

 all green, it has developed all the head and under surface 

 scarlet, the edges of the feathers of the back scarlet, the 

 tail blue above, the blue cheek and blue shoulder-patch 

 persistent; it will be noted that the xanthochroistic element 

 has been entirely suppressed, though the cyanistic has main- 

 tained its usual standard. Variation in this species is 

 notable and interesting. At the extremities of its range, it 

 has become smaller and melanistic, while it is suggested that 



