WONDERS OF THE MICROSCOPE 255 



condor previously shown, will quite account for 

 their difference in outward appearance. 



Another example from the same order of flii^-ht- 



Vig. 174. A portion of the feather of a humming 

 biT-d. sliow ing how tlie barbs interlace 



less birds is given in Fig. i y/. This represents the 

 feather of an emu, whose plumage somewhat resem- 

 bles long tur as it hangs down on either side of the 

 bird's body from the central parting line which 

 runs down the middle of the back. Penguins — 

 birds which dive and swim instead of flying — 

 develop but small and scaly feathers 



