228 CALIFORNIA ACADEMY OF SCIENCES. 



colour is caused by a pigment termed capsicin, which 

 can be separated from the pepper; and it might easily 

 be supposed that the change from yellow to red in the 

 feathers of the canary was simply caused by a trans- 

 ference of the pigment * * but Dr. Sauermann 

 has shown that it is not so. Yellow-coloured canaries 

 were not in the very slightest degree affected by the pig- 

 ment alone; but, curiously enough, parti-coloured birds 

 did react, the brown parts of the feathers becoming 

 distinctly lighter in hue. It is a fatty substance 

 (triolein) which appears to convey the pigment, and 

 produce thus a changing of the colour from yellow to 

 red; and further experiments were made .with other 

 birds, showing that it is not only canaries which are in- 

 fluenced by their food in this way. Some white fowls, 

 belonging to a special breed, showed traces of yellow 

 among the feathers after feeding with cayenne; but in 

 this case there were not racial but individual differences 

 in susceptibility, for all the specimens of the birds ex- 

 perimented with did not react to the stimulus. 



A similar series of experiments was made with some 

 other colours: it was found with carmine that the yellow 

 colour was destroyed and the birds became white. This 

 unexpected effect is explained by the fact that a mixture 

 of violet and yellow produces white. The proof that the 

 fatty constituent, triolein, plays the chief part in the 

 colouring of the feathers may perhaps help to explain 

 the very singular fact that the Amazon parrots change 

 from green to yellow when fed upon the fat of certain 

 fishes. 



With regard to the white fowls referred to, the ex- 

 periments made by Dr. Sauermann were particularly in- 

 teresting. The interest lies in the fact that the pigment 

 was not absorbed equally by all the feathers; only special 

 tracts were affected; the breast feathers, for instance, 



