284 



DOMESTIC DUCKS. 



Chap. VIII. 



the pelvis than in the wild duck. The Aylesbury dnck has fifteen cervical 

 and ten dorsal vertebrae furnished with ribs, but the same number of 

 lumbar, sacral, and caudal vertebrae, as far as could be traced, as in the wild 

 duck. The cervical vertebrae in this same duck (fig. 40, D) were much broader 

 and thicker relatively to their length than in the wild (C) ; so much so, 

 that I have thought it worth while to give a sketch of the eighth cervical 

 vertebra in these two birds. From the foregoing statements we see that 

 the fifteenth cervical vertebra occasionally becomes modified into a dorsal 

 vertebra, and when this occurs all the adjoining vertebrae are modified. 

 We also see that an additional dorsal vertebra bearing a rib is occasionally 

 developed, the number of the cervical and lumbar vertebrae apparently 

 remaining the same as usual. 



I examined the bony enlargement of the trachea in the males of the 

 Penguin, Call, Hook-billed, Labrador, and Aylesbury breeds; and in all 

 it was identical in shape. 



The Pelvis is remarkably uniform ; but in the skeleton of the Hook-billed 

 duck the anterior part is much bowed inwards; in the Aylesbury and 

 some other breeds the ischiadic foramen is less elongated. In the sternum, 

 furcula, coracoids, and scapula, the differences are so slight and so variable 

 as not to be worth notice, except that in two skeletons of the Penguin 

 duck the terminal portion of the scapula was much attenuated. 



In the bones of the leg and wing no modification in shape could be 

 observed. But in Penguin and Hook-billed ducks, the terminal phalanges 

 of the wing are a little shortened. In the former, the femur and meta- 

 tarsus (but not the tibia) are considerably lengthened, relatively to the 

 same bones in the wild duck, and to the wing-bones in both birds. This 

 elongation of the leg-bones could be seen whilst the bird was alive, and is 

 no doubt connected with its peculiar upright manner of walking. In a 

 large Aylesbury duck, on the other hand, the tibia was the only bone 

 of the leg which relatively to the other bones was slightly lengthened. 



On the effects of the increased an d decreased Use of the Limbs.— -In all the breeds 

 the bones of the wing (measured separately after having been cleaned) rela- 

 tively to those of the leg have become slightly shortened, in comparison with 

 the same bones in the wild duck, as may be seen in the following table :— 



Name of Breed. 



Wild mallard . 

 Aylesbury .. 

 Tufted (Dutch) 

 Penguin 

 Call 



Length of Femur, 

 Tibia, and Meta- 

 tarsus together. 



Inches. 



7-14 



8-64 

 8-25 

 7-12 

 6-20 



Length of Humerus, 

 Radius, and Meta- 

 carpus together. 



Inches. 



•28 

 ■43 

 •83 

 •78 



•77 



Or as 



100 : 129 

 100 : 120 

 100 : 119 

 100 : 123 

 100 : 125 



Wild duck (another specimen) 

 Common domestic duck 



Length of same 

 Bones. 



Inches. 

 6-85 

 8-15 



Length of all the 

 Bones of Wing. 



Inches. 

 10-07 

 11-26 



100 : 147 

 100 : 138 



