478 MANUAL OF ZOOLOGY SECT. 



as in the Frog ; the narrow eustachian tubes open by a 

 common aperture (Fig. 270, eus. ap) in the roof of the 

 pharynx. 



The kidneys (Fig. 270, kd, Figs. 273 and 274, K) have a 

 very characteristic form. Each is a flattened organ divided 

 into three main lobes, and fitted closely into the hollows of 

 the pelvis. The ureters (ur) are narrow tubes passing 

 directly backwards to open into the middle compartment of 

 the cloaca. 



The testes (Fig. 273, ts) are ovoid bodies, varying greatly 

 in size according to the season, attached by perito- 

 neum to the ventral surfaces of the anterior ends of 

 the kidneys. From the inner border of each goes off a 

 convoluted vas deferens (vd), which passes backwards, 

 parallel with the ureter, to open into the cloaca on the 

 extremity of a small papilla. The posterior end of the 

 sperm-duct is slightly enlarged to form a vesicula seminalis 

 (v.s\ The female organs (Fig. 274) are remarkable for the 

 more or less complete atrophy of the right ovary and 

 oviduct. The left ovary (ov) is a large organ in the adult 

 Bird, its surface studded with follicles or ovisacs, varying 

 in size from about 15 mm. in diameter downwards, and 

 each containing a single ovum. The left oviduct (L od) is 

 long and convoluted ; its anterior end is enlarged to form 

 a wide, membranous coelomic funnel (/. od") into which the 

 ripe ova pass on their liberation from the ovisacs ; the rest 

 of the tube has thick muscular walls, lined with glandular 

 epithelium, and opens into the cloaca. 



Internal impregnation takes place. As the ova or 

 "yolks " pass down the oviduct they are invested with the 

 secretions of its various glands ; first with layers of albttmen 

 or " white," next with a parchment-like shell-membrane, and 

 lastly with a white calcareous shell. They are laid, two at a 



