200 



DK. P. CHALMEKs MITCHELL ON THE 



Phcenicopteri. 



Phcenicopterii)^. — In Fhoenicopterus ruber (tig. 21) the duodenum is a simple loop, 

 but with a slight Heron-like twist. Meckel's tract is very much elongated as in 

 Platalea, and, again as in that bird, it consists of very many short loops symmetrical 

 about the middle mesenteric vein which runs towards a Meckel's diverticulum. As in 

 Plaialea tliis region is twisted into a rude spiral, and there is a well-formed sujjra- 

 duodenal loop. The caeca are long, and the rectum is of moderate length but straight. 

 The only Anserine feature in the intestinal tract of the Flamingo is the presence of long 

 caeca; and this, as we shall see in the further course of this memoir, is an obviously 

 multu'adial apocentricity. In all other respects the intestinal tract of the Flamingo is 

 that of a low Ciconiiform bird. 



Fig. 2L 



-->'X 



Intestinal Tract of Phcenicoj>ieriis rulicr. Lettering as before. 



It is unnecessary to do more than sum up in a few words the conditions of the gut 

 found among the Ciconiiform birds. The ground-form is closely similar to tliat of the 

 Colymbomorphie, pointing towards the existence of a common metacentre for all these 

 birds. From this metacentre the groups of Ciconiiformes have diverged in different 

 directions and to different amounts. The Steganopods sliow a tendency to the bunching 

 up of the loops of Meckel's tract on the axis given by the middle mesenteric vein. The 

 Herons display a tendency to the individual elaboration of the minor loops of Meckel's 

 tract. The Ciconiine birds show the most definitely uniradial apocentricity, 'consisting 

 of an elaboration and intimate connection between the duodenum and the first looji of 

 Meckel's tract, with a reduction of the posterior portion of Meckel's tract, except the 

 supra-duodenal loop. The Ibidid*, or at least Platalea, show a primitive elaboration of 

 Meckel's tract as a whole, and this tendency is carried further in the Flamingoes. 



