ON THE BURSA FABRICII IN BIRDS. 

 Fig. 4. 



13 



Cloaca of Casuarius uniappendiculatus, viewed from behind. 



a, a. Cut surface of posterior wall of bursa. b. Opening of cloacal chamber into 

 bursa. c. Pointer passing from cavity of bursa to exterior, d'. Pointer passed 

 from cloaca into bursa through opening b ; the upper part is supposed to be seen 

 through the wall of cloaca, e. Clitoris. 



narrow, cylindrical tube, the central cavity of which becomes closed up 

 as atrophy advances. In (Edicnemus there is a similar form of bursa. 

 In Attac/is, on the other hand, the form is pyriform, more like that of the 

 Passeres and Gallinse. 



In Larus I found the bursa represented by a small pouch. In the 

 young Uria troile it is large and sac-like, and slightly curved from side 

 to side (see fig. 2, p. 9). The walls are very glandular, and so thick 

 that the central cavity is but small. There are no crests. In an adult 

 Alca tor da it was reduced to a pore-like opening. 



In none of the Tinami that I have dissected have I found any bursa ; 

 on the other hand, the posterior wall of the third cloacal chamber is 

 covered with numerous glands arranged in a tree-like manner. 



In all the birds hitherto mentioned (with the exception of Plotus) the 

 bursa, as we have seen, opens by a more or less constricted aperture into 

 the general cavity of the cloaca. In the Struthious birds, however, the 

 very opposite is the case. The cloaca (or at least as much of it as 

 corresponds to the first and second chambers) opens into the bursa Fabricii. 

 This will perhaps be best explained by looking at fig. 4, represent- 

 ing the cloaca and bursa of a not full-grown Cassowary (Casuarius 



P. Z. S. 1877, 

 p. 314. 



