THE rEIIfAET AND GEJTEEATITE SYSTEMS. 209 



pair of caeca there may be a single caecuiii or there may be 

 nothing o£ the kind whatever. 



The rectum opens posteriorly into the terminal chamber of 

 the alimentary canal, which is called the cloaca. The latter is 

 a capacious rounded space, into which the urinary and generative 

 ducts also open, the whole communicating with the exterior by 

 a single aperture, the vent. 



A glandular structure, called the bursa Fabricii, also opens 

 upon the wall of the cloaca into its cavity. 



A gland, called the pancreas, which supplements by its secre- 

 tion the action of the saliva, lies embraced by the duodenal 

 fold of the Latestiae. Two or three ducts from it enter the 

 intestine near its commencement. A little further down, the 

 ducts of the liver convey its secretion, the bile, into the intes- 

 tine. It is divided into two main lobes, and may or may not 

 be provided with a gall-bladder. 



A small round or oval body, called the spleen, lies not far 

 from the stomach. 



The TJErN-AKY and G-enbeatite Systems. 



The urinary system consists of two kidneys, the ducts of 

 which — the ureters — pass backwards and open into the cloaca, 

 behind where the alimentary canal opens into it. The kidneys 

 are soft in texture, and sometimes — as in the Grebe and Coot- 

 are more or less blended together at their hinder ends. They 

 are dark-coloured and firmly fixed upon the ventral sur- 

 face of the dorsum of the trunk, especially within those 

 cavities of the sacrum before described *. At the anterior end 

 of either kidney is a small yellowish body named the supra^ 

 renal capsule. 



The testes, or essential male organs, are a pair of oblong or 

 more elongated bodies placed on the ventral side of the ante- 

 rior part of the kidneys. Each consists of a mass of most 

 minute and highly convoluted tubes. The testes vary much 

 in size according to the season of the year, enlarging greatly 

 at the breeding-season. Their secretion is conveyed outwards 

 by two long, more or less convoluted tubes — the vasa deferentia 

 ■ — which pass back beside the ureters and open, each on a 

 papilla, in the cloaca, one on each side of the openings of 



* See ante, p. 174. 



