308 The Bird 
of blood-like scarlet in the centre of its breast? The re- 
markable and inexplicable resemblance is heightened 
by the stiffened vanes of the centre feathers, causing them 
to appear bedraggled and clotted, as if by an actual wound! 
The photograph does but little justice to the bird’s real 
appearance. 
Another class of colours, while still protective, is so 
for a purpose very different from those cases which we 
Fic. 245.—Bleeding-heart Pigeon. 
have been considering. The colours which we are now 
to mention have been aptly called aggressive colours, as, 
by their means, a bird of prey is enabled to approach 
its victim more easily. So, throughout the entire animal 
world we find two phases of phenomena constantly pres- 
ent: on the one hand the pursued ones, striving to escape 
by all means in their power; and on the other hand the 
pursuers, ever trying to outwit those upon which they 
prey. If a duck acquires great speed of flight, the Duck 
