1896.] INTESTINAL TRACT OF BIRDS. . 145 



slight spiral twist, the axis of which is the middle mesenteric vein, 

 which runs out to the yolk-duct vestige. The last loop and the 

 third part of the intestine, and the veins, are as in the Spoonbill. 



Ciconia alba, Ciconia nigra (fig. 9), Leptoptilus crumeniferus, 

 and Leptoptilus argila show the tendency to form spirals which is 

 present throughout this group in an increasing degree. In these 

 four birds the duodenum forms a spiral which, in C. nigra, is 



Fig. 9. 



Ciconia nigra ; intestinal tract, x, short-circuiting vessel divided. 



twisted with a spiral formed from the first subsidiary loop of the 

 circular loop. The remainder of the circular loop is elongated in 

 them all, and the yolk-duct vestige occurs at the elongated point. 

 The last loop of the cii'cular system and the third part of the gut 

 and the veins occur in the fnshion typical of the whole group. 



Pelecanus fuscus, which is the only Steganopod I have examined, 

 displays a simple variety of the CiconiiforQi type. The duodenum 

 is straight and encloses a curiously lobulated pancreas. The 

 circular coil begins with a short straight minor loop, and then 

 forms an enormous bunch of short equally sized loops, supplied by 

 radiating branches of the middle mesenteric vein. Upon one of 

 these, nearer the posterior than the anterior end, occurs the yolk- 

 duct vestige. The end of the circular loop is drawn out into the 

 usual loop, with a short-circuit vein from the duodenum, and the 

 third part of the gut is as in the other Ciconiiformes. 



Ansbbifoembs. 



The striking character of the Anseriformes is the small deviation 

 from the primitive type represented in their intestines. As I have 

 already pointed out in a communication on the anatomy of GJiauna, 

 the gut of that bird has deviated from the avian type even less 

 than the gut of the Ostrich. The result is a very striking similarity 

 between the gut of the Struthious birds, of Ckauna, and of an 



Proc. Zool. Soc— 1896, No. X. 10 



