140 TlMEHRt. 
cidental source whatever. The ash of turacine is pure, 
black copper oxide. The pigment is only present in the 
red feathers : and the birds, when bred in England and 
kept in confinement, produce the same copper pigment. 
The plantain fruits, on which the birds chiefly feed, have 
been found to contain distinct traces of copper. 
We see from this, then, that the red colour in these 
birds is due to the presence of turacine, and that the 
formation of turacine depends on the presence of the 
metal copper in the food material. The chief food 
material that supplies the copper seems to be plantain. 
If, therefore, food other than plantain, food in which no 
copper was present, alone was supplied to the birds, it 
would be an impossibility for them to elaborate turacine^ 
and they would thus be unable in the course of time, 
to supply the place of any red feathers, which might be 
lost, with feathers of the same hue. If, therefore, under 
these conditions, the feathers were plucked out after 
some time had elapsed, or the bird moulted, the new 
feathers must take on some other colour, dependent on 
the kind of pigment produced under the changed condi- 
tions of life — a pigment the nature of which could only 
be determined by experiment in each individual case. 
It would be extremely interesting to have determina- 
tions made of the different pigments that impart charac- 
teristic colours to the feathers of birds, the purples, 
blues, greens, yellows, oranges and reds ; to determine 
whether similar colours in different groups of birds were 
due to the presence of similar pigments ; and to ascer- 
tain the changes in pigments, and hence the changes of 
coloration, produced by withholding from the birds that 
kind of food containing what may be looked upon as the 
