CHAPTER XX 



THE BIRDS (Continued) 



THE order Ratitae includes six families of birds Ostriches or 

 Struthiones, Rheas or N audits, Cassowaries and Emus or Megistanes, 

 Kiwis or Apteryges, Moas or Dinornithes, and Rocs or Aepyornithes 

 the last two families being extinct. 



The Ratita are a primitive group of birds characterised by 

 having no keel to the sternum ; greatly reduced wings, useless 

 as flying organs ; feathers having free barbs, not held together 

 by hooked barbules ; the absence of the curious " ploughshare " 

 bone at the end of the tail ; and the construction of the skull, which 

 differs from that of all flying birds, with the exception of the 

 tinamou. 



They have been described by Professor W. K. Parker as " over- 

 grown, degenerate birds that were once on the right road for 

 becoming flying fowl, but through greediness or idleness never 

 reached the ' goal ' went back, indeed, and lost their sternal 

 keel, and almost lost their unexercised wings." The generally 

 accepted theory is, however, that the Ratita are descended from 

 birds which once possessed the power of flight, but lost it in con- 

 sequence of the abundance of food and scarcity of enemies in 

 the areas they frequented, which rendered flight unnecessary ; and 

 that the small wings of the ostrich and the mere vestiges seen in 

 the cassowary, emu, and kiwi are degenerate and not incipient. 

 The fact that every degree of the degeneration of the wing can 

 be traced down to its entire disappearance in certain extinct moas 

 is brought forward in proof of this theory by W. P. Pycraft, who 

 argues that if this is not a case of degeneration, " we must suppose 

 the wings (of the present types of Ratitse) to have developed from 

 nothing ; and this would imply that the earliest birds were de- 

 scendants of creatures wherein the fore-limb had disappeared, 

 and in time reappeared in the form of a minute useless organ, 



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