Feet and Legs 361 
in which birds have inherited the earth. When we realize 
the immense advantage which the power of flight gives 
to them, we do not marvel at this remarkable distribu- 
tion, but the more we think about it the more wonders 
appear. The utmost efforts which man has made to 
reach the North Pole have shown flocks of birds winging 
their way still farther to the North, heedless of the ter- 
rible cold. In the heat of deserts and the sweltering 
jungles of the tropics, birds find congenial haunts and 
abundant food. Thousands of miles out at sea, on the 
highest mountains, and even in dark underground tun- 
nels; the whole day—twilight, midnight, and dawn,— 
all have been conquered by these tireless, energetic feath- 
ered ones. 
When we see a large collection of birds, we can appre- 
ciate how they are adapted to such varying conditions 
of temperature, of moisture, of light, and of altitude. 
Their bodies, wings, legs, feet, and tails—in fact every 
organ and member is of all sizes and shapes, and shows to 
what condition of life the individual is suited. But when 
we come to know birds better, and we realize that there 
are wheels within wheels, that behind these very evident 
divisions into Families and Orders there are lesser groups, 
among the members of which the competition is no less 
keen, we look for and find gentler gradations and adapta- 
tions which, in their way, are more to be wondered at 
than the larger, more radical differences; for these birds 
have changed their habits and haunts without waiting 
for Nature to adjust their wings or their feet. They have 
taken the initiative as it were, and, like a man of letters 
