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Show 144 ME. P. CHALMERS MITCHELL ON THE [Jan. 14, gated, the greater part of the elongation having occurred in the circular loop. The caeca are small, and lie on the third part of the gut, some distance below where it joins the circular loop. As usually happens when the caeca are reduced, the last part of the circular loop is pulled out into a long free loop, which, in the natural position, is closely attached to the under surface of the duodenum, and gives a vein to the duodenal vein. Platalea leuco- Fig. 8. Platalea leucorodia ; intestinal tract, x, short-circuiting vessel cut across. rodia, the Spoonbill (fig. 8), shows the least differentiation among those that I have examined. The duodenum is very long and is curved far round to the left in the abdominal cavity. The circular loop is enormously expanded, and forms a rough spiral, of which the middle mesenteric vein, running out to the vestige of the yolk-duct, forms the axis. The figure represents this after it has been dissected out and is more diagrammatic than most of the drawings I give. The most important points to which I would call attention are: that the yolk vestige, though at the end of the spiral, is much nearer the posterior than the anterior end of the circular loop, owing to the greater development of the first half of the circular loop ; and the fact that on the whole the minor loops of the circular loop are of similar length, with the exception of the last loop. It is in this respect especially that the Spoonbill has departed less than other Ciconiiformes from the type. The veins of the gut are almost diagrammatic in the simplicity of their arrangement, the only peculiarity being the short-circuiting branch from the duodenal vein to the distal loop of the circular loop. In Pseudotantalus ibis the duodenum, which was curved in Platalea, is very much elongated and twisted into a spiral. The first portion of the circular loop is elongated into a separate loop: the remainder of the circular loop is more primitive even than in Platalea, consisting of a number of nearly equal radial folds at the circumference of the whole fold. There is a very |