1896.] INTESTINAL TRACT OF BIRDS. 153 
of the circular loop is expanded. In Pterocles it forms a long 
narrow loop, the end of which is bent upon itself. The posterior 
Fig. 18. 
Pterocles bicinctus ; intestinal tract. «x, short-circuiting vessel divided. 
part of the circular loop remains in the primitive condition, and 
has the long cca attached to it. A short-circuiting vein from 
the duodenum is present. The rectum is straight. 
In the Columbe which I have examined (Colwmbe of several 
species, Phlogenas cruenta) (fig. 19), it is tempting to regard the 
Fig. 19. 
Columba livia; wtestinal tract ; the spiral is figured as rather too symmetrical. 
«, short-circuiting vessel divided. 
