short, are ‘‘instinctive.’’ Those with defective instincts 
are forthwith killed by falling to the ground. They leave no 
offspring to inherit their defects. 
Perhaps the most convincing evidence of all as to the 
“instinctive ’’ nature of flight, in nestling birds, is furnished 
by the mound-birds, of the Malay Region and Eastern 
Australia. 
These extraordinary birds lay their eggs in heaps of 
decaying vegetable-matter, or in the soil near hot springs ; 
and there leave them to their fate. They lay very large eggs, 
it is to be noticed, so large that the growing chick finds 
nourishment enough within the egg to enable it to pass the 
ordinary nestling stage while still within the shell. By the 
time it emerges it has both grown and shed its first coat of 
nestling-down, and has developed long wing-quills. Having 
burst its prison walls it wriggles its way up through the loose 
earth to the light of day, ready to fight its way in the world 
unaided. Here, then, there can be no question of “ teaching ”’ 
the young to fly. 
But some birds, at least, do, indeed, receive instruction 
when on the wing. And in such cases, it will be noticed, their 
food can only be captured by dexterous movements in full 
flight. For a day or two, for example, young swallows simply 
practice flight, to exercise and strengthen their wings. They 
are fed by their parents when at rest. The next step comes 
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