158 ON THE INTESTINAL TRACT OF BIRDS. (Jan. 14. 
Colies (fig. 24) have the same parts, but still wider and shallower. 
At first sight the gut of the Coly seems very different from that of 
the Hornbill. But the vestige of the yolk-duct orients the apex 
of the middle subsidiary loop of the mid-gut: the anterior and 
posterior loops of the mid-gut may then be seen as simple shallow 
curves on the gut. The wide duodenum and the straight rectum, 
and the veins, are as in the Hornbill and Woodpecker. 
PASSERIFORMES. 
I have proceeded only a short way in the examination of the 
members of this vast group, but those that I have examined 
show a simple and identical modification of the common type. 
Parus major (fig. 25) may serve as a fairly generalized example of 
the Passerine type. The duodenum isasimpleloop. The circular 
coil of the mid-gut shows a tendency to be spirally twisted, the 
Fig. 25. 
Parus major ; intestinal tract. 2, short-circuiting vessel divided. 
vestige of the yolk-duct forming the apex of the spiral, and the 
median mesenteric vein forming the axis of the spiral. The spiral is 
hardly visible in Parus ; it forms jess than halfa turn. In the Crows 
and Nutcrackers, and in a very large number of other Passeres, the 
spiral is long and forms several turns. Between the spiral and 
the rectum there is a subsidiary loop on the mid-gut where in the 
primitive type the ceca ran forwards. This in Parus and in all 
other Passeres I have examined is closely connected with the 
duodenum, which is folded under it. Frequently a lobe of the 
pancreas passes across and lies in this subsidiary loop. The loop 
has a recurrent vein from the middle mesenteric vein, and a short- 
circuiting vein or veins opening into the duodenal vein. The 
rectum is short and straight, and where these are present, as in 
Parus, bears the ceca. The veins are normal. 
Some Passeres, as, for instance, the Nutcracker, show signs of a 
subsidiary loop of the mid-gut between the spiral and the duode- 
num. In others, as, for instance, the Poé Honey-eater (Prosthe- 
madera), the anterior part of the mid-gut and the spiral are reduced 
to practically a simple fold, while the last loop of the mid-gut is 
considerably expanded. 
7 
