158 ON TUB INTESTINAL TBAOT OP BIEDS. [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. 



PASSEEirOEMES. 



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 is a simple loop. The circular 

 coil of the mid-gut shows a tendency to be spirally twisted, the 



Fig. 25. 



Pants major ; intestinal tract, x, 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 less than half a 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 cajca 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 iu 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 cajca. The veins are normal. 



Some Passeres, as, for instance, the Nutcracker, show signs of a 

 subsidiary loop of the uiid-gut between the spiral and the duode- 

 num. In others, as, for instance, the Poij Honey-eater (ProstJie- 

 ■madera), the anterior part of the mid-gut and the spiral are reduced 

 to practically a sim])le fold, while the last loop of the mid-gut is 

 considerably expanded. 



