ON THE BURSA FABRICII IN BIRDS. 



11 



even these disappear finally. The process of atrophy in the other species 

 which he observed is essentially the same as that in the Fowl. 



I now proceed to describe the general characters of the bursa Fabricii 

 in the groups of birds I have examined. In the Passeres it is usually 

 small, pyriform, with a small opening and glandular walls without ridge- 

 like elevations on the interior. It seems to disappear completely in 

 adult birds. In the RhamphastidaB it disappears in the adult, only leaving 

 a small pore to mark its place of opening. In the Cuculidae it presents 

 a very characteristic shape, the peduncle being long and thin, and the 

 extremity club-shaped, giving the whole somewhat the appearance of a P. Z. S. 1877, 

 shortened and clumsy antenna of a butterfly (see fig. 3). It disappears P* ~' 



Fig. 3. 



Cloaca and Bursa of Geococcyx affinis. 



The cloaca is cut short and laid open from before. The narrow peduncle of the 

 bursa is supposed to be seen through the cloaca, a. "Yesical sphincter.' b. 

 Bursa. c. Opening of same, d, d'. Ureter and opening, e, e' . Vas deferens 

 and opening. 



completely in adult birds. In specimens of Dacelo gigantea, Merops, 

 and Momotus lessoni it was sac-like and of considerable size. In the 

 Parrots it is well marked and bag-like, opening by a small pore. As 

 already mentioned, in an old specimen of Platycercus icterotis I found the 

 bursa well marked, though its opening into the cloaca was nearly 

 obliterated. In a specimen of Stringop* I found no bursa. In the 

 Accipitres it forms a moderate-sized pyriform sac ; in old birds this 

 becomes reduced to a sort of small conical pouch in the substance of the 

 back wall of the cloaca at the place of aperture. Of the Steganopodes, 

 in Phalacrocorax (2 species) and Sula bassana the bursa is a large sac, 

 l|-2 inches in length, which opens by a small pore in the usual places. 

 The walls of the bursa are very thick ; they are traversed by about seven 

 rows of large, irregular, crypt-like pores, separated by smooth, narrowed, 

 raised ridges. The ridges and pores disappear towards the base of the 

 bursa ; but the upper part has a curious honeycomb-like appearance, some- 

 what like that of the Ruminant reticulum. The internal surface is covered 

 with numerous, small, opaque, granular-looking corpuscles, especially 



