ON THE BURSA FABRIC1I IN BIRDS. 7 



Francolinus vulgaris, GAVI^B. 



F. Ucalcaratus. Larus ridibundus. 



Euploctimus cristatus. 



PTGOPODES. 

 Argus yis/anteus. 



Meleagris meviccma. Uria troile ' 



Alca torda. 



ALECTORIDES. TINAMI. 



Otis tarda. Rhynchotus rufesccns. 



Grus carunculata. Crypturus tatupa. 

 Serpentarius reptilivorus. 



Oeydromm australis. STRUTHIONES. 



Porphyno alien i. Struthio camelus. 



P. marlinieus. Rhea americana. 



P. poliocephalus. Dromceus novce-hollandice. 



Hydrophasianus chiruryus. Casuarius beccarii. 



C. picticollis. 



GEALLJ;. ^ uniappendiculatus. 



(Edicnemus crepitans. Apteryx mantdli. 



Attagis, sp. A. oweni. 



For an opportunity of examining a specimen of the last I am indebted 

 to Prof. Newton's kindness. 



If the cloaca of an ordinary bird be taken and laid open in front (i. e. p. z. S. 1877, 

 on the ventral surface) along the middle line, the rectum will be seen P* ^' 

 to terminate at the top of a more or less well-marked chamber, which 

 usually is iwore capacious than the terminal part of the alimentary tract, 

 from which it is generally separated off by a more or less plain valvular 

 constriction, the different nature of the two parts being also frequently 

 shown by the differences in the character of the mucous membrane lining 

 them. Below the entrance of the rectum, on the posterior wall of the 

 cloaca, and disposed symmetrically as regards the median line on the 

 sides of which they He, are the openings of the uro-genital ducts, fre- 

 quently elevated on papillae, which vary in shape in different birds. Of 

 these the ureters open nearest the middle line ; externally to them are 

 the openings or opening of the vasa deferentia or oviduct, which latter 

 is fully developed only on one side, though sometimes a trace of it may 

 be seen on the other also. Above the uro-genital papillae in many birds 

 (e. g. Meleagris mexicana and Tetrao urogallus) is a well-marked valvular 

 fold of mucous membrane, which thus separates off the upper portion 

 of this " cloaca " from that part into which the urino-genital ducts open. 

 Below these, again, is a similar, but usually better-marked fold (the 

 vesical sphincter of St.-Ange), which is present in all the birds I have 

 examined, in a more or less developed state. Below this in the middle 

 line, and also on the posterior wall, is seen (if the specimen be not too 

 old) a circular hole of varying dimensions. This is the opening of the 



