2S4 COLOUR IN NATURE chap. 



the reduced condition. The pigment, like carmine, 

 behaves as an acid, being readily soluble in dilute 

 alkalies, but insoluble in acids. 



Turacin is generally supposed to be confined to 

 the plantain-eaters, but it has been also described 

 by Krukenberg in one of the cuckoos {Dasylophus 

 superciliosus). The use, meaning, and origin are 

 alike unknown ; its importance in coloration appears 

 to be relatively slight, the feathers in which it occurs 

 frequently showing bluish structural colour in addition 

 to the red colour due to turacin. It is somewhat 

 interesting to note that the family of the plantain- 

 eaters is an exceedingly small one of very limited 

 distribution — it occurs in Africa only. 



If turacin be boiled for a long time in air, it loses 

 its red colour and becomes green, the change, accord- 

 ing to Krukenberg, indicating the conversion into a 

 new pigment. This new pigment he describes as 

 being devoid of copper, but containing a considerable 

 amount of iron ; its spectrum shows a single band, 

 instead of the two of turacin itself. This green 

 pigment was found by Krukenberg in the green 

 feathers of Corythceola crisiata, one of the Musopha- 

 gidae in which turacin is absent, and of Corythaix 

 albicristata, one in which it is present. This seems 

 therefore to be one of those interesting cases of 

 chemical relations existing between the different 

 pigments of allied genera — a subject of which we 

 know only too little. Church is, however, inclined 

 to doubt the existence of an independent green 

 pigment. 



Another interesting pigment of similarly restricted 

 distribution is the red colouring-matter to which the 



