DIVING BIRDS AT THE ZOO 
79 
stand, with wings spread out to dry, and the light 
shining through the pink skin and membranes, their 
descent from some very early form of bird suggests 
itself at once, though the anatomists forbid us to 
jump to the conclusion that the darters are saurian- 
birds as the penguins are seal-birds. 
The submarine flight of the penguin is perhaps the 
most beautiful form of animal movement known ; 
certainly it is the most beautiful which we can see and 
admire with our own eyes. The motions of flight in 
the air, though now analyzed and laid before us in the 
exquisite drawings of M. Marey, must always remain 
something which must be taken on faith ; transcripts 
made by other eyes than ours, records of the camera 
and the sun. The true movements of flight, so made 
familiar to our brain, may in part be detected after- 
wards by the naked eye. Yet the speed and direction 
of birds’ flight in air, and the necessary distance 
between them and ourselves, which every beat makes 
greater, must always leave it something of a mystery. 
But the change of medium from air to water gives an 
added charm to flight. The substitution of aqueous 
for aerial poise detracts nothing from the wonderful 
powers of the wing. But it adds two conditions. In 
the first place, the whole scene is directly cognizable 
by our senses. All the wonderful phenomena of 
flight can be watched from a distance of a few feet, 
or even inches, from the eye. The simile of the 
caged butterfly does not apply to the diving bird in 
its tank, which exhibits its powers, pursuing its prey 
