PIGEON'S BREAST-BONE. 69 



Under domestication there would be a suspension 

 of the previous elimination of reduced breast- 

 bones by natural selection (Weismann's panmixia), 

 and a diminution of the parts concerned in flying 

 might even be favoured, as lessened powers of 

 continuous flight would prevent pigeons from stray- 

 ing too far, and would fit them for domestication 

 or confinement. Such causes might reduce some of 

 the less observed parts affected by flying, while 

 still leaving the wing of full size for occasional 

 flight, or to suit the requirements of the pigeon- 

 fanciers. A change might thus be commenced 

 like that seen in the rudimentary keel of the 

 sternum in the owl-parrot of New Zealand, 

 which has lost the power of flight although 

 still retaining fairly-developed wings. 



the rock-pigeon in size. We can hardly suppose that use-inherit- 

 ance especially affects the eight breeds that have varied most in size. 

 If we exclude these, there is only a total shortening of 7 per cent, to 

 be accounted for. 



