230 THE HISTOEY OF CREATION. 



still liviBg ostriches, also belong to this group. The Birds 

 of the ostrich kind — by giving up the habit of flying, by 

 the degeneration of the muscles for flying resulting from this, 

 and of the breast bone which serves as their support, and 

 by the corresponding stronger development of the hinder 

 legs for running — have probably arisen out of a branch of 

 the Keel-breasted birds. But possibly, as Huxley thinks, 

 they may be the nearest relations of the Dinosauria and of 

 the Reptiles akin to them, especially of the Compsognathus ; 

 at all events, the common primary form of all Birds must 

 be looked for among the extinct Reptiles. 



