AVES. 229 



CHAPTER XL AVES. 

 16. COLUMBA LIVIA (The Rock-Pigeon). 



The common Rock-Pigeon is here selected for description, but 

 it must be remembered that the very numerous fancy breeds 

 have all been derived from this form. In some few places the 

 structure of the Fowl (G-allus bankiva) is alluded to, where it 

 differs markedly from the Pigeon. 



MORPHOLOGY AND PHYSIOLOGY. 



1. External Characters. The bilaterally symmetrical body, in 

 addition to head and trunk, possesses a long flexible neck, and a 

 short stumpy posterior process, the tail (uropygium). Fore- and 

 hind-limbs are present, the former modified into wings, the latter 

 set on to the body very far forwards, thus securing equilibrium, 

 and facilitating bipedal progression. The body is largely, but 

 not entirely, covered with feathers, arranged in definite tracts 

 (pterylce), there being intervening bare spaces (apteria). There 

 are several kinds of feathers, the largest, quill-feathers, present on 

 the wings and tail, are those principally used in flight. The 

 wing-quills (remiges) are 19 in number on each side. They are 

 overlapped, above and below, by smaller wing-coverts. The tail- 

 quills (rectrices), 12 in number, are attached to the uropygium, 

 and are overlapped on both sides by tail-coverts. The small soft 

 feathers, which invest all parts of the body, and confer the 

 characteristic outlines, are contour-feathers. In addition to these 

 a very great number of minute rudimentary feathers are present, 

 the filoplumes. 



The head is well rounded behind, while in front it tapers into 

 the beak, the upper and lower parts of which are encased in horn, 

 and bound the large mouth. A bare elevated area, the cere, is 

 present at the base of the upper division of the beak, and in 

 front of this two slit-like nostrils (external nares). The large 

 eyes possess upper and lower featherless eyelids, and each is 

 provided as well with a thin translucent third eyelid (nictitating 

 membrane) which can be quickly drawn over the eye, or folded 



