INTESTINAL TRACT OF BIRDS. 



isls 



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 caica are relatively much 

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

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



Fis:. 5. 



Intestinal Tract of Pafliclpes cri.ftatus. 

 X, bridging factor of the duodenal vein draining S.D.F., the supra-duodenal looj) ; ?, probable 



position of Meckel's diverticulum. 



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

 birds, it appears tliat Avhilc the character of the gut has moved outwards from the archc- 

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

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

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

 with any other group. 



