INTESTINAL TRACT OP BIEDS. 189 



length in association with the nature of their food, and certainly multiradial ; second, 

 Meckel's tract in all, while remaining nearly symmetrical, tends to be drawn out into a 

 series of long, narrow, and straight loops, a feature which may give some clue to affinity ; 



Fig. 9. 



Intestinal Tract of Diomeclea exulans. Lettering as before. 



third, the rectum in all is very short. The Colymbiformes are least modified; the 

 Penguins and Petrels are more modified, the two latter showing degeneration of the 

 caeca and certain peculiarities in the posterior portion of Meckel's tract, peculiarities 

 repeated in Steganopodes and Falconiformes. 



CICONIIFORMES. 



STEGANOPODES. 



(1) PHAETHONTID.E. Phaethon (fig. 10) displays a simple form of alimentary tract. 

 The duodenal loop is simple ; Meckel's tract is thrown into a series of narrow, minor 

 loops, some of which are slightly complicated by folding. Meckel's diverticulum occurs 

 on one of the minor loops rather more near the distal end of the tract. The posterior 

 portion has no special supra-duodenal loop, and ends in a portion drained by the rectal or 



SECOND SERIES. ZOOLOGY, VOL. VIII. 30 



