INTESTJNAL TEACT OF BIRDS. 



185 



similar. Two of the minor loops of Meckel's tract are carried out to a great length, one 

 of them bearing Meckel's diverticulum at its summit ; the caeca "are relatively much 

 longer, and the supra-duodenal loop is still more highly specialized. The Podicipedes, 

 then, present an apocentricity rather more marked than that of the Divers. 



Fig:. 5. 



Intestinal Tract of Podieipes cristatus. 



x, bridging factor of the duodenal vein draining S.D.F., the supra-duodenal loop ; ?, probable 



position of Meckel's diyerticulum. 



When allowance has been made for the size and piscivorous habits of the Colymbiform 

 birds, it appears that while the character of the gut has moved outwards from the arche- 

 centric position chiefly in the direction of the formation of specialized straight loops 

 (according to Gadow's nomenclature, the folding is orthocoelous), the apocentricity is not 

 great, and is certainly not of such a uniradial character as to associate them closely 

 with any other group. 



