INTESTINAL TRACT OF BIRDS. 



251 



Meckel's tract is short, and forms a circular expanse with the diverticulum nearly at 

 the central point. The posterior region of the tract, however, shows traces of former 



Fig. 69. 



Intestinal Tract of Oi/pselits apus. 



complexity, in that it is drained partly by a bridging vein, a circumstance to which 1 

 attach importance as evidence that the apparent simplicity of the gut is pseudocentric. 

 The caeca are absent, and the rectum is straight and wide. 



TROCHILID^E. I have examined a number of Humming-birds, and found that the 

 conformation of the gut was in every case practically identical with that in Cypselm. 

 It is worth while pointing out that the Humming-birds differ clearly in the conformation 

 of the gut from the Passerine Nectariniidae, although in both the small size has brought 

 about a remarkable simplicity. The Nectariniidae possess the Passerine nipple-like caeca, 

 and show clear indications of the spiral twist in Meckel's tract which is a striking 

 Passer'ne character, and there is no trace of either of these peculiarities in the 



Humming-birds. 



COLII. 



I have already described and figured the intestinal tract of Coitus capemis (26. fig. 21). 

 It is relatively shorter and wider than in any other bird that I have examined, and this 

 modification, no doubt due to small size and frugivorous habit, has obliterated practically 

 completely the underlying morphological form. The gut consists of a very wide 

 duodenum, a Meckel's tract bearing a small diverticulum, and consisting of a simple 

 loop similar to the duodenum in size and appearance, and a short, wide rectum. There 

 are no traces of caeca. 



