58 ARE THE EFFECTS OF USE INHERITED? 



skeleton, then the apparently reduced weight of 

 the wing-bones is fully accounted for by the same 

 circumstance, and disuse has had no inherited 

 effect. 



Another strange circumstance is that the wing- 

 bones have diminished in length only. The shorten- 

 ing is about 6 per cent, more than in the shortened 

 legs, and it amounts to n per cent, as compared 

 with the weight of the skeleton. Such a shortening 

 should represent a reduction of 29 per cent, in 

 weight, whereas the actual reduction in the weight 

 of the wing-bones relatively to the weight of the 

 skeleton is only 9 per cent, even in the breeds 

 that never fly. Independently of shortening, the 

 disused wing-bones have actually thickened or 

 increased in weight. In the Aylesbury duck 

 the disproportion caused by these conflicting 

 changes is so great that the wing-bones are 

 47 per cent, heavier than they should be if 

 their weight had varied proportionally with their 



