1896.] 



INTESTINAL THACT OF BIEDS. 



147 



resemblance to the Ostrich is heightened by tlie fact that iu 

 Chauna and the Ostrich the rectum, by being thrown into a sub- 

 sidiary set of folds, departs in a similar way from the common type. 

 The resemblance between Chauna and lihea is very striking. 



The Ducks and Geese (fig. 11) display a very definite and simple 

 modification of the ground-type. It consists simply in the elon- 

 gation of a limited number, generally five, of the primitive irregular 

 loops of the circular loop. In a young Bernirla magellanica, still 

 in its down plumage, the duodenum and the third part of the gut 

 were in the typical condition, but the circular loop was already 

 pulled out into three or four subsidiary loops, of which the longest 

 bore the yolk-duct vestige. In adult Ducks, Geese, and Swans 

 the arrangement differed in no' essential respect from the drawing 



Fig. 11. 



Cygnus atratus ; intestinal tract. a\ sbort-circuiting vessel divided. 



(fig. 11). The duodenum was simple. The duodenal vessel received 

 short-circuiting veins from the hinder portion qf the circular loop.. 

 A striking feature of the minor loops on the front part of the 

 mid-gut is the presence upon them of minor loops. The circular- 

 loop had a huge median mesenteric vein, which ran out to the 

 much elongated .subsidiary loop bearing the yolk-duct. It gave- 

 off three vessels to three expansions of the pioximal part of the 

 circular loop, vessels to a long and short distal expansion, and a 

 vessel to the straight part of the loop along which the caeca were 

 attached. The rectum was straight and in the typical fashion 

 was supplied by a posterior mesenteric vein. 



Falconifobmes. 



I have not had the opportunity of examining any of the Cathartse. 

 The Accipitres show a marked divergence from the common type. 

 The gut generally is enormously long, especially in the fish-eaters. 

 From the point of view of relation to type, I cannot see that there 

 is any special relation between the Accipitrine deviation and the 



10* 



