298 



DOMESTIC DUCKS. 



Chap VIII, 



fifteen cervical and nine dorsal vertebrae ; in a third skeleton small 

 ribs were attached to the so-called fifteenth cervical vertebra, 

 making ten pairs of ribs ; but these ten ribs do not correspond, or 

 arise from the same vertebra, with the ten in the above-mentioned 

 Labrador duck. In the Call duck, which had small ribs attached 

 to the fifteenth cervical vertebra, the haemal spines of the thirteenth 

 and fourteenth (cervical) and of the seventeenth (dorsal) vertebrae 

 corresponded with the spines on the fourteenth, fifteenth, and 

 eighteenth vertebrae of the wild duck: so that each of these 

 vertebrae had acquired a structure proper to one posterior to it in 



position. In the eighth cervical 

 vertebra of this same Call duck 

 (fig. 40, B), the two branches of the 

 haemal spine stand much closer 

 together than in the wild duck 

 (A), and the descending haemal 

 processes are much shortened. 

 In the Penguin duck the neck 

 from its thinness and erectness 

 falsely appears (as ascertained by- 

 measurement) to be much elon- 

 gated, but the cervical and dorsal 

 i) vertebrae present no difference; 

 the posterior dorsal vertebrae, 

 however, are more completely 

 anchylosed to the pelvis than in 

 the wild duck. The Aylesbury 

 duck has fifteen cervical and ten 

 dorsal vertebrae furnished with 

 ribs, but the same number of 

 lumbar, sacral, and caudal verte- 

 brae, 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 twelfth 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 p'dvlft 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 



Fig. 4°. — Cervical Vertebrae, of natural size. 

 A. Eighth cervical vertebra of Wild Duck, 

 viewed on haemal surface. B. Eighth 

 cervical vertebra of Call Duck, viewed as 

 above. C. Twelfth cervical vertebra of 

 Wild Duck viewed laterally. D. Twelfth 

 cervical vertebra of Aylesbury Duck, 

 viewed laterally. 



