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Certain birds (e.g., Ostrich, Duck) have a copulatory organ 

 or penis. The right ovary atrophies, and the right oviduct 

 is reduced. The eggs are large, contain much yolk and 

 albumen, and are enclosed in limy shells ; the embryo has 

 an amnion, an allantois, and a large yolk-sac. 



Birds are oviparous, feathered bipeds, which have the 

 fore-limbs modified as wings ; they are warm-blooded, and 

 the efficiency of their respiratory mechanism is superior 

 to that of Mammals^ 



The Pigeon (Columba). 

 A Type of Birds. 



Briefly enumerate the External Features of the Pigeon. 



The head is produced into a horny toothless beak, above 

 the base of which is the sensory cere, overhanging the 

 nostrils (external nares). Eyes with eyelids and, at the 

 anterior angles, a third eyelid or nictitating membrane. 

 Ear openings (external auditory meatus) behind the eyes. 

 Neck well- developed. Trunk deep, prominent keel vent- 

 rally ; tail short. Preen gland above, and cloaca below 

 base of tail. 



The feathers are attached along definite tracts or pterylae, 

 the intervening featherless areas are the apteria. A large 

 feather shows the following structure : Stem or axis con- 

 sisting of a lower hollow part, the calamus or quill, and an 

 upper solid rachis or shaft, which bears the vane. The 

 vane is composed of numerous barbs, along each side of the 

 rachis, held together by minute barbules which have hook- 

 lets. The quill has at its proximal end an aperture, the 

 inferior umbilicus ; and at its distaj end, just below the 

 vane, is the superior umbilicus (near which, in many birds, 

 there is a tuft called the aftershaft). The different kinds 

 of feathers are, (1) quills, (2) smaller contour feathers of 

 body, (3) down or plumules (absent in pigeon), (4) filo- 

 plumes. The tail quills (rectrices) are used for steering ; 

 the wing quills (remiges) are either primaries (those attached 

 to bones of the manus or hand) or secondaries (attached to 

 ulna). A small tuft of feathers borne by the first digit 

 (thumb) is the bastard wing. Some of the contour feathers 

 are coverts, which overlie the bases of the wing and tail 

 quills. The fine filoplumes (seen on the skin after plucking) 

 are hair-like with a few terminal barbs. The four clawed 

 toes, and the tarso-metatarsal part of the leg, are covered 

 with scales. 



