ANATOMY OF THE SHOE-BILL. 665 



the ureter until the latter nearly had reached the wall of the 

 cloaca, and then twisted outwards. A transverse fold also sepa- 

 rated the urodseum from the pi'octodseum (text-fig. 124, B). In 

 the proctodfeum, at each side and just at the edge of the sphincter, 

 were four or five little glandular ajjertures leading into small 

 cavities lined with irregular ridges. I find in my notes of dissec- 

 tions of Ostriches, both male and female, that similar glandular 

 crypts are 2:)resentin that bird. In the middle line of the procto- 

 dseum, just behind the fold separating that chamber from the 

 urodfeum, lies the large, elongately oval aperture of the Bursa 

 FabricJi (text-fig. 124, F). The bursa is a very large chamber, 

 lying above the cloaca, running forwards almost to the rectum. 

 The inner wall is lined by irregular, heavy ridges, making it 

 resemble the reticulum of a ruminant stomach. In the figure, 

 part of the dorsal wall of the coprodseum and urodaeum is repre- 

 sented as cut away to show the cavity. The bursa was empty. 

 There was no trace of a penis. 



Our knowledge of the Bursa Fabricii is due chiefly to Foi'bes, 

 later writers having added very little to his observations and 

 conclusions (9). In Struthious birds, especially when they are 

 young, there is practically no constriction separating the procto- 

 dseum and the bursa, the latter being simply a forwardly 

 directed and dorsally placed continuation of the cavity of the 

 posterior division of the cloaca. In the diflerent groups of birds 

 there appears to be a genei'al tendency for a convei'gent modifica- 

 tion of this simple arrangement ; the constriction between procto- 

 dseum and cloaca becomes more and more pronounced, until the 

 bursa becomes a tubular or pyrifonn sac opening by a very small 

 pore into the dorsal wall of the cloaca. This progressive change 

 is most marked in Passerines and in those birds in other groups 

 which most nearly mimic the passerine type, and may lead to the 

 complete disappearance of the aperture and of the bursa. There 

 is of course no reasonable doubt but that the Passerines present 

 the most specialized results of avian evolution. To a certain 

 extent, ontogenetic changes in the bui\«;a show a similar course of 

 change, the aperture of the bursa narrowing, and the bursa itself 

 tending to contract and even to disappear with age. There is 

 probably, therefore, no special significance in the condition of the 

 bursa in the example of Balcuniceps I dissected, its large size and 

 wide aperture being perhaps due to youth. Forbes, however, 

 states that in the Storks and Herons he examined, the bursa was 

 large and its aperture small. He also mentions the absence in 

 these birds of the reticulum of ridges in the lining wall of the 

 bursa, although he found them in Steganopods much as I describe 

 them in Balceniceps. I cannot draw any systematic conclusions 

 from these facts. 



A small penis is stated to be present in Storks, absent in 

 Herons, so that in the absence of thnt organ Balcenicejis resembles 

 the latter group, but I attach no systematic value to this. 



