STRUCTURE AND CLASSIFICATION OF BIRDS 



get broader in the lumbar region ; they finally completely 

 fuse to form a broad and uninterrupted tract. 



The ventral tract is undivided in the neck in Otis ; it is 

 very broad in the pectoral region, where it divides into two 

 narrow bands, with an indication of a third in the form of a 

 slightly divergent outer group of particularly strong feathers. 

 The two pairs of narrow tracts unite round the cloaca. 



In Eupodotis australis the dorsal tract is divided high up 

 on the neck, the ends of the tracts at ends of scapula are 

 particularly strongly feathered, arid the two halves of the 

 posterior region of the dorsal tract run in anteriorly between 

 the anterior forks. The ventral tract has a fainter indication 

 than in Otis of the outermost branch. It does not appear 

 again to divide into two. 



A striking peculiarity of the bustards is the variability of 

 the carotids. In Otis and Honiara there are two ; \i\Eitpo- 

 dotis only the right ; in Tetrax only the left. 



The following are intestinal measurements :- 



The caecum of Otis tarda is highly remarkable. The 

 median third of the gut is much dilated, and is lined by a 

 smooth mucous membrane, which is marked by about seven 

 slightly raised longitudinal folds, which are visible externally, 

 but connected with no sacculation. Scattered about are 

 numerous circular glands, of the size of hemp seed. The 

 terminal part of each caecum, which is some two inches in 

 length, has villi, like intestine. The apical region has not, 

 but there is a close retiforrn disposition of mucous membrane, 

 which gradually passes into longitudinal folds of the middle 



