286 



DOMESTIC DUCKS. 



Chap. VIII. 



Name of Breed. 



Wild mallard . . 



Aylesbury 



Tufted (Dutch) . . . 



Penguin 



Call (from Mr. Fox) 



Weight of entire 

 Skeleton. 

 (N.B. One Metatar- 

 sus and Foot was 

 removed from each 

 skeleton, as it had 

 been accidentally lust 

 in two cases.) 



Grains. 



839 



1925 



1404 



871 



717 



Wild mallard 



Aylesbury 



Tufted (Dutch) 



Penguin 



Call (from Mr. Baker) 

 Call (from Mr. Fox) 



Weight of Skeleton 

 as above. 



Grains. 

 839 

 1925 

 1404 

 871 

 914 

 717 



Weight of 

 Femur, Tibia, 

 and Metatarsus. 



Grains. 



54 

 164 

 111 



75 



57 



Or as 



1000 : 64 

 1000 : 85 

 1000 : 79 

 1000 : 86 

 1000 : 79 



Weight of 

 Humerus, 

 Radius and 

 Ulna, and Meta- 

 carpus. 



Grains. 



97 

 204 

 148 



90 

 100 



92 



1000 

 1000 



115 

 105 



1000 : 105 

 1000 : 103 

 1000 : 109 

 1000 : 129 



table we see, with, the exception of one case, a plain reduction in the weight 

 of the bones of the wing, and this no doubt has resulted from their lessened 

 use. The one exceptional case, namely, in one of the Call-ducks, is in truth 

 no exception, for this bird was constantly in the habit of flying about ; 

 and I have seen it day after day rise from my grounds, and fly for a long 

 time in circles of more than a mile in diameter. In this Call-duck there 

 is not only no decrease, but an actual increase in the weight of the wing- 

 bones relatively to those of the wild duck ; and this probably is consequent 

 on the remarkable lightness and thinness of all the bones of the skeleton. 



Lastly, I weighed the furcula, coracoids, and scapula of a wild duck and 

 of a common domestic duck, and I found that their weight, relatively to 

 that of the whole skeleton, was as one hundred in the former to eighty- 

 nine in the latter ; this shows that these bones in the domestic duck have 

 been reduced eleven per cent, of their due proportional weight. The pro- 

 minence of the crest of the sternum, relatively to its length, is also much 

 reduced in all the domestic breeds. These changes have evidently been 

 caused by the lessened use of the wings. 



It is well known that several birds, belonging to different 

 Orders, and inhabiting oceanic islands, have their wings greatly 

 reduced in size and are incapable of flight. I suggested m 

 my 'Origin of Species' that, as these birds are not persecuted 

 by any enemies, the reduction of their wings has probably been 

 caused by gradual disuse. Hence, during the earlier stages of the 



