WONDERS OF THE MICROSCOPE 255 



condor previously shown, will quite account for 

 their difference in outward appearance. 



Another example from the same order of flight- 



. 174. A portion of the feather of a humming 

 bird, showing how the barbs interlace 



less birds is given in Fig. 177. This represents the 

 feather of an emu, whose plumage somewhat resem- 

 bles long fur 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 



