INTESTINAL TRACT OF BIRDS. ' 



215 



completely lost the caeca. Pandion stands by itself; its gut is so extremely long that 

 none of the usual minor loops except the supra-caecal kink can be identified. Haliaetus 

 is a simple modification of the Falconiform metacentre, the irregularity being due to 

 increase in length. For the Anseridae it is necessary to go back to the Pelargo-Colymbo- 

 morphine metacentre. Anseranas is practically in that position unmodified, save that 

 the caeca are still longer, a condition common to all the Anseridae except some of the 

 Mergansers. The Cygnus type, with its three definite and contorted minor loops on 

 the anterior portion of Meckel's tract and its very long axial loop with peculiar blood- 

 vessels, gives an Anserine metacentre from which Nettopus and Spatula have diverged 

 still further. Mergus is probably a pseudocentric modification of the Spatula type. 



TINAMIFORMES. 



CRYPTTTRID^E. Of these I have been able to examine the intestinal tract of several 

 specimens of Rhynchotus rufescens and Nothura maculosa. The conformation is prac- 

 tically identical in these two forms. The duodenum is a long narrow loop ; Meckel's 

 tract (Rhynchotus rufescens, fig. 36) is divided into two nearly equal parts, the large 



Fig. 36. 



Intestinal Tract of Rhynchotus rufescens. 

 c, compare loop similarly marked in Gruiformes, figs. 41, 42, 43, &c. Other lettering as before. 



Meckel's diverticulum lying between the two. The first portion is one very long narrow 

 loop ; the second portion is an equally long and narrow supra-duodenal loop drained by a 

 branch of the middle mesenteric vein as well as by the usual " bridging " factor from the 

 duodenal vein. Meckel's diverticulum was very large in two specimens of Rhynchotus, 

 small in a third, and very small in Nothura. The small minor loop just distad of it 



33* 



