The Body of a Bird 289 
in the apteryx and emeu (Tig. 23). Compare a feather 
of the latter with one of a condor and the difference is 
remarkable. So unfeatherlike is the emeu’s plume and 
so loose are its barbs that it brings to mind the much- 
divided leaflets of an Acacia. 
The plumage of the snake-bird is inexplicable. This 
bird is so emphatically aquatic that we would expect 
a dense, compact covering of the body; but in reality 
it more nearly resembles hair or fur, soaking through so 
quickly and thoroughly that, after immersion for some 
time, the bird becomes waterlogged and has to hang 
itself out to dry by seeking some sunlit perch, opening 
wide its wings and waving them to and fro. 
The feathers of the penguin are small, flat, and rigid, 
approaching in these respects the scales of fishes—an 
interesting reacquiring of characters consequent upon 
an all but wholly aquatic life. It is interesting to com- 
pare the colouring of such a bird as the Scaled Partridge 
with a fish like the Carp, the dark margins of the feathers 
and scales bringing about a remarkable resemblance. 
Taking up the subject of colour in general, we realize, 
after even a superficial glance at a collection of birds, 
that in gorgeousness of hue and diversity of shade and pat- 
tern, they are to be compared only with insects. In a 
former chapter we have briefly considered the chemical 
and optical causes of colour in feathers; but the causes 
due to environment (using that word in its widest sense) 
cover a vastly greater field and one as vet comparatively 
unexplored. 
Advancement of actual knowledge of any subject in 
