206 



UlRl) CALI.KHV. 



Colour. — The coluiir of leathers is due to one of three causes. : — 

 (1 ) It may arise frt)ni tlie pi'esence of actual pigment, (2) from pigment 

 overlaid by colourless structures, or (3) from irideseeuee due to the (-fleet 

 of light falling on tlic polished, ridircd or pitted surfaces of the feather 

 which act as piisms. . , ■ . 



Vvs. IV. . ' • ' -., . 



Side view of HiplU Foot of a Piirplu (Jiilliuuli/ (Poi-phi/riu) to sliovv tlie 

 composition of the lioniy coveriug (pudot/iecd). 



1 . Hallux ur hind toe. 



2. Inner toe. 



3. Middle loe. 



4. Outer toe. 



o. Scales (,Sciitr//fe). 



(i. Ueticulate sciiles. 



Yellow colour, like black, brown and red, is as a rule due to pigment 

 diffused througliout the substance of the feather. Some yellow feathers, 

 however, contain no pigmeut whatever, the colour being due to the 



