The Body of a Bird 289 



in the apteryx and emeu (Fig. 23). Compare a feather 

 of the latter with one of a condor and the difference is 

 remarkable. So imfeatherlike 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 bod}" but in reality 

 it more nearly resembles hair or fur, soaking through so 

 quickl}" 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 reacquirmg 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 yet comparatively 

 unexplored. 



Advancement of actual knowledge of any subject in 



