1896.] ~ INTESTINAL TRACT OF BIRDS. 141 
described frequently, were marked by the attachment of a spiral 
valve. But the rectal part of the intestine, that supplied by the 
Fig. 4. 
tes Struthio camelus ; intestinal tract. .«, short-circuiting vessel cut across. 
posterior mesenteric vein, is expanded into an enormous coil 
swung at the circumference of a semicircular expansion of its 
mesentery. Only in Chauwna and in the Eagles and Petrels have 
I found the slightest trace of a convergent resemblance to this 
feature, but in the latter the subsidiary rectal loops, although sup- 
plied by the rectal vessel, lie above the cxca. 
I have not yet had an opportunity of dissecting a Rhea or an 
Apteryx 1. 
It is plain that, so far as degree of divergence of type in the 
alimentary canal goes, the Ratites deserve their accepted place at 
the bottom of the avian scale. 
CARINATA. 
COLYMBIFORMES. 
In these (Podiceps not examined) (fig. 5, p. 142) the duodenal loop 
is straight and normal. The circular loop is pulled out into a series 
of minor loops that are arranged almost symmetrically round the 
middle mesenteric vein. The yolk-sac vestige lies in front of the 
middle point of the series. The last loop of the circular system 
? [In a Rhea americana which I have more recently examined the gut was 
intermediate in form between those of Caswarius and Struthio. The anterior 
portion resembled Caswarius; the rectum had an expansion recalling that in the 
Ostrich, but much less strongly marked.—P. OC. M., March 1896.] 
