194 



DE. P. CHALMEES MITCHELL ON THE 



tightly or much elongated as a whole. These two forms of modification of the middle 

 loop point towards the condition found in many of the Ibididse sucli as Platalea, and in 



Fie. 15. 



Intestinal Tract of Pelecanus rvfescens. Letterins; as before. 



the Flamingoes, where Meckel's tract, in the unfolded condition not unlike that of the 

 Pelican,l[is in life twisted irregularly into a spiral. I find, then, in the apocentricity of 

 the Steganopod Meckel's tract an underlying resemblance to that of the Colymbomorphae, 

 as if a metacentric position had been common to all these, but from this metacentre the 

 two sets have diverged in difi'erent directions. The reduction of the cseca, the shortening 

 of the rectum, and the formation of minor loops above the cseca, but drained by the 

 posterior mesenteric vein, are common, Intt not invariable, in the whole set. 



