| OCR Text |
Show 1896.] INTESTINAL TRACT OF BIRDS. 145 slight spiral twist, the axis of which is the middle mesenteric 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 ft nigra, is Fig. 9. Ciconia nigra ; intestinal tract, .r, short-circuiting vessel divided. twisted with a spiral formed from the first subsidiary loop of the circidar 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 circular system and the third part of the gut and the veins occur in the fashion typical of the whole group. Pelecanus fuscus, which is the only Steganopod I have examined, displays a simple variety of the Ciconiiform 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. ANSERIFORMES. 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 Chauna, 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 Chauna, and of an PROC. ZOOL. Soc-1896, No. X. 10 |
