148 MR. P. CHALMERS MITCHELL ON THE [Jan. 14, 
deviation among the Pelargi, although Dr. Gadow has laid some 
stress on the existence of such a resemblance. In some of the 
Vultures and Falcons there are spirals formed by the subsidiary 
loops, just as occurs, for instance, in Ciconia (fig. 9). On the 
other hand, members of both groups exhibit a much simpler 
method of attaining increased length, and this seems to imply 
that the spiral formation is a convergent resemblance. When 
the simplest members of the groups are taken—I am speaking 
of them only from the point of view of gut-formation—the special 
spiral formation disappears and the relations between the groups 
are only their relations to the common type. The White-tailed 
Sea-Eagle (fig. 12) shows the general character of the group. Its 
gut is very long, and if the spiral twists were a character of the 
Fig. 12. 
Haliaétus albicilla ; intestinal tract. 2, short-circuiting vessel divided. 
group one would expect the increased length to be displayed in 
the formation of complicated spirals. This does not occur. The 
duodenum is thrown into a complicated set of subsidiary loops, 
thus recalling the similar modification in the Penguin. Among 
the Accipitrines generally the duodenum is a very wide irregular 
loop, but I have not found it thrown into secondary loops in other 
cases. The circular loop forms a very extended set of minor 
loops, some of which, especially on the lower side, are slightly 
twisted into spirals. In other Accipitres it is more often the 
upper loops of this series that are twisted. The vestige of the 
yolk-duct occurs at the end of the median mesenteric vein in the 
typical fashion, but is situated rather nearer the proximal end of 
the loop. The last loop of the circular system is very long and 
usually, as in Haliaétus, spirally twisted. It gives a short-circuiting 
vein to the duodenal vein. The part of the hind gut between the 
ceca and the circular loop is thrown into a complicated set of folds, 
