Feet and Legs 391 
cause the toes of these birds are all bound together with 
a single web. The hind toe points almost in a forward 
direction when the foot is in action, and, to complete 
the adaptation for a perfect swimming foot, the outer 
toe is the longest, a rare condition among birds. If one 
will watch the snake-birds in a zoological park, as they 
swim about their glass tank, the extreme delicacy of the 
foot mechanism becomes apparent at once. 
Not only is the flat side of the leg used as a cutwater, 
but the toes curl and uncurl with a slight oblique revolving 
motion like the blades of a propeller. When drawn for- 
ward through the water they are rolled up into a very 
small compass and then instantly spread out as widely 
as possible on the return stroke. To the eye it seems 
as if the bird was constantly grasping something tangible 
in the water and thrusting it behind. 
This propeller motion may be observed even better 
in a captive grebe. If the bird’s head is placed in a glass 
of water, its feet will move back and forth in the air with 
all the motion of swimming. The adaptation for swimming 
in these birds is so fundamental and thorough that even 
the claws are broadened and flattened until they resemble 
finger-nails. On land, grebes are absurdly awkward, 
although they can walk upright even up a slight incline. 
But they are powerless to rise from the ground, even 
with the aid of the wind,—needing the greater speed which 
a swimming take-off from the water will give them. 
The most aquatic of all birds, the penguins, make 
much more use of their wings than of their feet in swim- 
ming and diving. The toes are webbed, however, and 
