190 



DE. P. CHALMERS MITCHELL ON THE 



posterior mesenteric vein and exliibiting' a short supra-csecal kink. The caeca are 

 reduced, but not to the same extent as in other Steganopodes except the Pelicans. The 

 rectum is extremely short. The three factors of the portal vein are of diagrammatic 

 simplicity. 



Fig. 10. 



Intestinal Tract of Phaethon fla I'lrostris. Lettering ;is before. 



(2) SilLiD^. — In Sula bassana (fig. 11) the apocentricity of Phaethon is carried 

 further. The general arrangement is similar, hut the duodenum is longer and is com- 

 pound ; certain of the minor loops of Meckel's tract are longer, especially the last, that 

 forming a characteristic supra-duodenal loop with bridging vein ; and the kink on the 

 posterior part of Meckel's tract, that drained by the rectal vein, is larger. 



(3) Phalacrocoracid^. — In Phalacrocorax carlo (fig. 12) the duodenum is very long 

 and narrow ; Meckel's tract is extremely elongated, in which respect it resembles the 

 condition found in Platalea and Phatnicopterns, and is symmetrically disposed about the 

 middle mesenteric vein, which in the archecentric fashion runs from a large Meckel's 

 diverticulum. The supra-duodenal loop is long; there is a large supra-csecal kink 

 supjjlied by the rectal vein. The cseca are vestigial, and the rectum is relatively longer 

 that in Phaethon and Sula. In Plotus anhinga (fig. 13) the form of the tract presents 

 marked dhferences. The duodenum is similar. The anterior portion of Meckel's tract 

 is relatively much shorter, and consists of a single narrow loop, followed by one very 



